[tt] New Scientist: Evolution: 24 myths and misconceptions
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Evolution: 24 myths and misconceptions
New Scientist, 8.4.16
http://www.newscientist.com/channel/life/dn13620-evolution-24-myths-and-misconceptions.html
et seq.
It will soon be 200 years since the birth of Charles Darwin and 150years
since the publication of [75]On the Origin of Species,arguably the most
important book ever written. In it, Darwinoutlined an idea that many still
find shocking that all life onEarth, including human life, evolved through
[76]natural selection.
Darwin presented [77]compelling evidence for [78]evolution in On theOrigin
and, since his time, the case has become [79]overwhelming.Countless fossil
discoveries allow us to trace the evolution oftoday's organisms from earlier
forms. DNA sequencing has confirmedbeyond any doubt that all living
creatures share a [80]commonorigin. Innumerable examples of [81]evolution in
action can be seenall around us, from the [82]pollution-matching pepper moth
tofast-changing viruses such as HIV and H5N1 bird flu. Evolution is asfirmly
established a scientific fact as the roundness of the Earth.
And yet despite an ever-growing mountain of evidence, [83]mostpeople around
the world are not taught the truth about evolution, ifthey are taught about
it at all. Even in the UK, the birthplace ofDarwin with an educated and
increasingly secular population, one[84]recent poll suggests less than half
the population acceptsevolution.
For those who have never had the opportunity to find out aboutbiology or
science, claims made by those who believe in supernaturalalternatives to
evolutionary theory can [85]appear convincing.Meanwhile, even among those
who accept evolution, misconceptionsabound.
Most of us are happy to admit that we do not understand, say, stringtheory
in physics, yet we are all convinced we understand evolution.In fact, as
biologists are discovering, its consequences can bestranger than we ever
imagined. Evolution must be the best-known yetworst-understood of all
scientific theories.
So here is New Scientist's [86]guide to some of the most commonmyths and
misconceptions about evolution.
There are already [87]several [88]good and [89]comprehensive guides[90]out
there. But there can't be too many.
Shared misconceptions:
[These are the articles that are coming.]
[91]Everything is an adaptation produced by natural selection
[92]Natural selection is the only means of evolution
[93]Natural selection leads to ever-greater complexity
[94]Evolution produces creatures perfectly adapted to theirenvironment
[95]Evolution always promotes the survival of species
[96]It doesn't matter if people do not understand evolution
[97]"Survival of the fittest" justifies "everyone for themselves"
[98]Evolution is limitlessly creative
[99]Evolution cannot explain traits such as homosexuality
[100]Creationism provides a coherent alternative to evolution
Creationist myths:
[101]Evolution must be wrong because the Bible is inerrant
[102]Accepting evolution undermines morality
[103]Evolutionary theory leads to racism and genocide
[104]Religion and evolution are incompatible
[105]Half a wing is no use to anyone
[106]Evolutionary science is not predictive
[107]Evolution cannot be disproved so is not science
[108]Evolution is just so unlikely to produce complex life forms
[109]Evolution is an entirely random process
[110]Mutations can only destroy information, not create it
[111]Darwin is the ultimate authority on evolution
[112]The bacterial flagellum is irreducibly complex
[113]Yet more creationist misconceptions
[114]Evolution violates the second law of thermodynamics
References
75.
http://darwin-online.org.uk/EditorialIntroductions/Freeman_OntheOriginofSpecies.html
76. http://gregladen.com/wordpress/?p=144
77.
http://www.newscientist.com/article/mg18725132.000-what-ifdarwin-had-not-sailed-on-the-beagle.html
78. http://sandwalk.blogspot.com/2007/01/what-is-evolution.html
79. http://www.sciohost.org/ncse/kvd/Padian/Padian_transcript.html
80.
http://scienceblogs.com/pharyngula/2007/06/segmentation_genes_evolved_und.php
81.
http://www.newscientist.com/channel/life/mg19225834.000-review-2006-evolution-in-action.html
82.
http://www.newscientist.com/channel/opinion/mg19626330.500-reclaiming-the-peppered-moth-for-science.html
83. http://dx.doi.org/10.1126/science.1126746
84. http://news.bbc.co.uk/1/hi/sci/tech/4648598.stm
85. http://dx.doi.org/10.1126/science.319.5866.1034
86. http://www.newscientist.com/evolutionmyths
87.
http://www.sciam.com/article.cfm?chanID=sa013&articleID=000D4FEC-7D5B-1D07-8E49809EC588EEDF&pageNumber=1&catID=2
88. http://evolution.berkeley.edu/evolibrary/misconceptions_faq
89. http://www.talkorigins.org/indexcc/list.html
90. http://www.skepticreport.com/creationism/thingscreationistshate.htm
91.
http://www.newscientist.com/channel/life/dn13615-evolution-myths-everything-is-an-adaptation.html
92.
http://www.newscientist.com/channel/life/dn13616-evolution-myths-natural-selection-is-the-only-means-of-evolution.html
93.
http://www.newscientist.com/channel/life/dn13617-evolution-myths-natural-selection-leads-to-ever-greater-complexity.html
94.
http://www.newscientist.com/channel/life/dn13640-evolution-myths-evolution-produces-perfectly-adapted-creatures.html
95.
http://www.newscientist.com/channel/life/dn13687-evolution-myths-evolution-promotes-the-survival-of-species.html
96.
http://www.newscientist.com/channel/life/dn13621-evolution-myths-it-doesnt-matter-if-people-do-not-understand-evolution.html
97.
http://www.newscientist.com/channel/life/dn13671-evolution-myths-survival-of-the-fittest-justifies-everyone-for-themselves.html
98.
http://www.newscientist.com/channel/life/dn13639-evolution-myths-evolution-is-limitlessly-creative.html
99.
http://www.newscientist.com/channel/life/dn13674-evolution-myths-natural-selection-cannot-explain-homosexuality.html
100.
http://www.newscientist.com/channel/life/dn13688-evolution-myths-creationism-is-an-alternative-to-evolution.html
101.
http://www.newscientist.com/channel/life/dn13695-evolution-myths-the-theory-is-wrong-because-the-bible-is-inerrant.html
102.
http://www.newscientist.com/channel/life/dn13696-evolution-myths-accepting-evolution-undermines-morality.html
103.
http://www.newscientist.com/channel/life/dn13689-evolution-myths-evolutionary-theory-leads-to-racism-and-genocide.html
104.
http://www.newscientist.com/channel/being-human/dn13722-evolution-myths-religion-and-evolution-are-incompatible.html
105.
http://www.newscientist.com/channel/life/dn13683-evolution-myths-half-a-wing-is-no-use.html
106.
http://www.newscientist.com/channel/life/dn13677-evolution-myths-evolution-is-not-predictive.html
107.
http://www.newscientist.com/channel/life/dn13675-evolution-myths-evolution-cannot-be-disproved.html
108.
http://www.newscientist.com/channel/life/dn13694-evolution-myths-evolution-is-just-so-unlikely.html
109.
http://www.newscientist.com/channel/life/dn13698-evolution-myths-evolution-is-random.html
110.
http://www.newscientist.com/channel/life/dn13673-evolution-myths-mutations-can-only-destroy-information.html
111.
http://www.newscientist.com/channel/life/dn13633-evolution-myths-all-biologists-are-darwinists.html
112.
http://www.newscientist.com/channel/life/dn13663-evolution-myths-the-bacterial-flagellum-is-irreducibly-complex.html
113.
http://www.newscientist.com/channel/life/dn13717-evolution-myths-yet-more-misconceptions.html
114.
http://www.newscientist.com/channel/life/dn13720-evolution-myths-evolution-violates-the-second-law-of-thermodynamics.html
Evolution myths: Everything is an adaptation
We tend to assume that all characteristics of plants and animals
areadaptations that have arisen through natural selection. Many areneither
adaptations nor the result of selection at all.
Why do so many of us plonk ourselves down in front of the telly witha
microwave meal after a tiring day? Because it's convenient? Orbecause TV
meals are "the natural consequence of hundreds ofthousands of years of human
evolution"?
Stop laughing. You've probably made similar assumptions. For justabout every
aspect of our bodies and behaviour, it's easy to inventevolutionary "Just
So" stories to explain how they came to be thatway. We tend to assume that
everything has a purpose, but often weare wrong.
Take male nipples. Male mammals clearly don't need them: they havethem
because females do and because it doesn't cost much to grow anipple. So
there has been no pressure for the sexes to evolveseparate developmental
pathways and "switch off" nipple growth inmales. Some people claim the
female orgasm exists for the samereason as male nipples, though this is a
far more controversialidea.
Then there's our sense of smell. Do you find the scent of rosesoverwhelming
or do you struggle to detect it? Can you detect thedistinctive odour that
most people's urine acquires after eatingasparagus? People vary greatly when
it comes to smell, largely dueto chance mutations in the genes that code for
the smell receptorsrather than for adaptive reasons.
Yet other features are the result of selection, but not for thetrait in
question. For instance, the short stature of pygmies couldbe a side effect
of selection for early childbearing in populationswhere mortality is high,
rather than an adaptation in itself.
Multiskilled genes
Another reason why apparent adaptations can be side effects ofselection for
other traits is that genes can have different roles atdifferent times of
development or in different parts of the body. Soselection for one variant
can have all sorts of seemingly unrelatedeffects. Male homosexuality might
be linked to gene variants thatincrease fertility in females, for instance.
A non-adaptive or detrimental gene variant can also spread rapidlythrough a
population if it is on the same DNA strand as a highlybeneficial variant.
This is one reason why sex matters: when bits ofDNA are swapped between
chromosomes during sexual reproduction, goodand bad variants can be split
up.
Other features of plants and animals, such as the wings ofostriches, may
once have been adaptations but are no longer neededfor their original
purpose. Such "vestigial traits" can persistbecause they are neutral,
because they have taken on anotherfunction or because there hasn't been
enough evolution to eliminatethem even though they have become
disadvantageous. Take theappendix. There are plenty of claims that it has
this or thatfunction but the evidence is clear: you are more likely to
survivewithout an appendix than with one.
So why hasn't it disappeared? Because evolution is a numbers game.The
worldwide human population was tiny until a few thousand yearsago, and
people have few children with long periods between eachgeneration. That
means fewer chances for evolution to throw upmutations that would reduce the
size of the appendix or eliminate italtogether and fewer chances for those
mutations to spread throughpopulations by natural selection. Another
possibility is that we arestuck in an evolutionary Catch-22 where, as the
appendix shrinks,appendicitis becomes more likely, favouring its retention.
Wisdom teeth are another vestigial remnant. A smaller, weaker jawallowed our
ancestors to grow larger brains, but left less room formolars. Yet many of
us still grow teeth for which there is no room,with potentially fatal
consequences. One possible reason why wisdomteeth persist is that they
usually appear after people reachreproductive age, meaning selection against
them is weak.
For all these reasons and more, we need to be sceptical ofheadline-grabbing
claims about evolutionary explanations fordifferent behaviours. Evolutionary
psychology in particular isnotorious for attempting to explain every aspect
of behaviour, fromgardening to rape, as an adaptation that arose when our
ancestorslived on the African savannah.
Needless to say, without solid evidence, claims about how, forinstance, TV
dinners "evolved" should be taken with a large pinch ofsalt.
Evolution myths: Natural selection is the only means of evolution
Much change is due to random genetic drift rather than positiveselection. It
could be called the survival of the luckiest.
Take a look in the mirror. The face you see is rather different tothat of a
Neanderthal. Why? The unflattering answer could be for noother reason than
random genetic drift. With features that can varysomewhat in form without
greatly affecting function, such as theshape of the skull, chance might play
a bigger role in theirevolution than natural selection.
The DNA in all organisms is under constant attack from highlyreactive
chemicals and radiation, and errors are often made when itis copied. As a
result, there are at least 100 new mutations in eachhuman embryo, possibly
far more. Some are harmful and are likely tobe eliminated by natural
selection by death of the embryo, forinstance. Most make no difference to
our bodies, because most of ourDNA is useless junk anyway. A few cause minor
changes that areneither particularly harmful nor beneficial.
You might think that largely neutral mutations would remainrestricted to a
few individuals. In fact, while the vast majority ofneutral mutations die
out, a few spread throughout a population andthus become "fixed". It is pure
chance some just happen to be passedon to more and more individuals in each
generation.
Although the likelihood of any neutral mutation spreading by chanceis tiny,
the enormous number of mutations in each generation makesgenetic drift a
significant force. It's a little like a lottery: thechance of winning is
minuscule but because millions buy a ticketevery week there is usually a
winner.
As a result, most changes in the DNA of complex organisms over timeare due
to drift rather than selection, which is why biologistsfocus on sequences
that are similar, or conserved, when they comparegenomes. Natural selection
will preserve sequences with vitalfunctions, but the rest of the genome will
change because of drift.
Drifting through bottlenecks
Genetic drift can even counteract natural selection. Many slightlybeneficial
mutations can be lost by chance, while mildly deleteriousones can spread and
become fixed in a population. The smaller apopulation, the greater the role
of genetic drift.
Population bottlenecks can have the same effect. Imagine an islandwhere most
mice are plain but a few have stripes. If a volcaniceruption wipes out all
of the plain mice, the island will berepopulated by striped mice. It's a
case of survival not of thefittest, but of the luckiest.
Random genetic drift has certainly played a big role in humanevolution.
Human populations were tiny until around 10,000 yearsago, and went through a
major bottleneck around 2 million years ago.Other bottlenecks occurred when
a few individuals migrated out ofAfrica around 60,000 years ago and
colonised other regions.
There is no doubt that most of the genetic differences betweenhumans and
other apes and between different human populations aredue to genetic drift.
However, most of these mutations are in thenine-tenths of our genome that is
junk, so they make no difference.The interesting question is which mutations
affecting our bodies orbehaviour have spread because of drift rather than
selection, butthis is far from clear.
Evolution myths: Natural selection leads to ever greater complexity
In fact, natural selection often leads to ever greater simplicity.And, in
many cases, complexity may initially arise when selection isweak or absent.
If you don't use it, you tend to lose it. Evolution often takes awayrather
than adding. For instance, cave fish lose their eyes, whileparasites like
tapeworms lose their guts.
Such simplification might be much more widespread than realised.Some
apparently primitive creatures are turning out to be thedescendants of more
complex creatures rather than their ancestors.For instance, it appears the
ancestor of brainless starfish and seaurchins had a brain.
Nevertheless, there is no doubt that evolution has produced morecomplex
life-forms over the past four billion years. The toughquestion is: why? It
is usually simply assumed to be the result ofnatural selection, but recently
a few biologists studying our ownbizarre and bloated genomes have challenged
this idea.
Rather than being driven by selection, they propose that complexityinitially
arises when selection is weak or absent. How could thisbe? Suppose an animal
has a gene that carries out two differentfunctions. If mutation results in
some offspring getting two copiesof this gene, these offspring won't be any
fitter as a result. Infact, they might be slightly less fit due to a double
dose of thegene. In a large population where the selective pressure is
strong,such mutations are likely to be eliminated. In smaller
populations,where selective pressure is much weaker, these mutations
couldspread as a result of random genetic drift (see Natural selection isthe
only means of evolution) despite being slightly disadvantageous.
The more widely the duplicated genes spread in a population, thefaster they
will acquire mutations. A mutation in one copy mightdestroy its ability to
carry out the first of the original gene'stwo functions. Then the other copy
might lose the ability to performthe second of the two functions. As before,
these mutations won'tmake the animals any fitter such animals would still
look and behaveexactly the same so they will not be selected for, but they
couldnevertheless spread by genetic drift.
Use your mutations
In this way, a species can go from having one gene with twofunctions to two
genes that each carry out one function. Thisincrease in complexity occurs
not because of selection but despiteit.
Once the genome is more complex, however, further mutations can makea
creatures body or behaviour more complex. For instance, having twoseparate
genes means each can be switched on or off at differenttime or in different
tissues. As soon as any beneficial mutationsarise, natural selection will
favour its spread.
If this picture is correct, it means that there are opposing forcesat the
heart of evolution. Complex structures and behaviour such aseyes and
language are undoubtedly the product of natural selection.But when selection
is strong as in large populations it blocks therandom genomic changes that
throw up this greater complexity in thefirst place.
This idea might even explain why evolution appears to speed up
afterenvironmental catastrophes such as asteroid impacts. Such eventswould
slash the population size of species that survive, weakeningselection and
increasing the chances of greater genomic complexityarising through
non-adaptive processes, paving the way for greaterphysical or behavioural
complexity to arise through adaptiveprocesses.
Evolution myths: Evolution produces perfectly adapted creatures
You don't have to be perfectly adapted to survive, you just have tobe as
well adapted as your competitors. The apparent perfection ofplants and
animals may be more a reflection of our poor imaginationsthan of reality.
It's a theme repeated endlessly in wildlife documentaries. Again andagain we
are told how perfectly animals are adapted to theirenvironment. It is,
however, seldom true.
Take the UK's red squirrel. It appeared perfectly well adapted toits
environment. Until the grey squirrel arrived, that is, andproved itself
rather better adapted to broadleaf forests thanks, inpart, to its ability to
digest acorns.
There are many reasons why evolution does not produce "designs" thatare as
good as they could be. Natural selection's only criterion isthat something
works, not that it works as well as it might. Botchedjobs are common, in
fact. The classic example is the panda's thumb,which it uses to grasp
bamboo. "The panda's true thumb is committedto another role. So the panda
must... settle for an enlarged wristbone and a somewhat clumsy, but quite
workable, solution," wroteStephen Jay Gould in 1978.
As this example shows, evolution is far more likely to reshapeexisting
structures than to throw up novel ones. The lobed fins ofearly fish have
turned into structures as diverse as wings, fins,hoofs and hands. We have
five fingers because our amphibianancestors had five digits, not because
five is necessarily theoptimal number of fingers for the human hand.
Many groups simply never evolve features that might have made themeven more
successful. Sharks lack the gas bladder that allows bonyfish to control
their buoyancy precisely, for example, and insteadhave to rely on swimming,
buoyant fatty livers and, occasionally, agulp of air. Similarly, mammals'
two-way lungs are far lessefficient than birds' one-way lungs. And sometimes
creatures evolvefeatures that actually reduce their overall fitness rather
thanincrease it, such as the peacock's tail (see Evolution alwaysincreases
fitness).
Use it or lose it
Continual mutation also means that if you don't use it, you lose it.For
instance, many primates cannot make vitamin C, because of a genemutation.
This mutation makes no difference to animals that getplenty of vitamin C in
their diet. However, when the environmentchanges, such loss of function can
make a big difference, as oneprimate discovered on long sea voyages.
Evolution's lack of foresight can produce inherently flawed designs.The
vertebrate eye with its back-to-front wiring and blind spotwhere the wiring
goes through the retina is one example. Lateradaptations have compensated
for these problems to a large extentbut once natural selection fixes upon a
flawed, but workable,design, a species' descendants are usually stuck with
it.
An organism's fitness is also relative to its environment, which isusually
changing. There is a constant arms race going on betweenpredator and prey,
parasite and host. Many species have to evolvecontinuously just to maintain
their current level of relativefitness, let alone get fitter. As the Red
Queen says in Through theLooking Glass: "It takes all the running you can
do, to keep in thesame place."
Evolution's peak?
Humans are not running fast enough. Evolving through naturalselection is
about time and numbers. The number of new mutationsthat appear, and the
number of chances that natural selection has toeliminate the harmful and
favour the beneficial ones, depends on thesize of a population, the number
of offspring each individual hasand on the number of generations, among
other things.
We might like to think of ourselves as the most "highly evolved"species but,
in terms of how many rounds of mutation and selectionwe've undergone, we are
one of the least evolved species.
Around 10 billion new viral particles can be produced every day inthe body
of a person infected with HIV. By contrast, the total humanpopulation on
Earth was no more than a few million until a fewthousand years ago.
Furthermore, in a decade bacteria can produce 200,000 generations --about
the number of generations of humans there have been since ourlineage split
from that of chimpanzees. So it's hardly surprisingthat in less than a human
lifespan weve seen the evolution of newdiseases such as HIV and numerous
antibiotic-resistant bacteria.
Although human evolution has sped up in the past 10,000 years, weare
changing our environment faster still. As a result, instead ofbecoming
better adapted we are actually becoming less well adaptedto the world we are
creating. Think of the huge range of modernafflictions, from obesity and
allergies to short-sightedness anddrug addiction, we suffer from. Viruses
and bacteria might approachperfection, but we humans are at best a very
rough first draft.
Evolution myths: Evolution promotes the survival of species
The phrase "survival of fittest" is widely misunderstood (see'Survival of
the fittest' justifies everyone for themselves). Manywrongly assume it means
that evolution always increases the chancesof a species surviving.
Evolution sometimes results in individuals or populations becomingless fit
and may occasionally even lead to extinction.
There are several ways in which evolution can reduce the overallfitness of
individuals or of populations. For starters, naturalselection can take place
at different levels genes, individuals,groups and what promotes the survival
of a gene does not necessarilyincrease the fitness of the individuals
carrying it, or of groups ofthese individuals.
For example, parasitic DNA elements, or transposons, can spreadthrough a
population even though they make their host organisms lessfit. Transposons
are one cause of genetic diseases such ashaemophilia.
Similarly, selfish individuals may thrive at the expense ofaltruistic
individuals in a group making them the "fittest" eventhough they make the
group as a whole less competitive. Suchcheaters can have disastrous
consequences.
In 1932, J. B. S. Haldane suggested this could even lead to theextinction of
populations a phenomenon called evolutionary suicide.Models and some
experimental evidence suggest he was right.
For instance, when nutrients run low, individual myxobacteria
(slimebacteria) may come together to form a fruiting body to producespores.
Lab studies have shown that cheating myxobacteria that onlyproduce spores
and never help form the non-spore producing parts ofthe fruiting body can
drive populations to extinction.
Genes capable of driving populations to extinction might have apractical
use, however. Biologists are exploring the possibility ofreleasing
engineered parasitic DNA into populations ofmalaria-carrying mosquitoes.
There is concern that something similar could happen accidentally.Fish that
have been genetically modified to produce a growth hormonegrow faster and
larger, mature earlier and produce more eggs. Butthey are less likely to
survive in the wild than unmodified fish.According to the Trojan gene
hypothesis, a gene variant thatproduces such characteristics could spread
rapidly through a wildpopulation despite reducing individual fitness, and
eventually drivethe population to extinction.
Another way in which evolution can reduce a species' chances ofsurvival is
through the accumulation of detrimental mutations.Mutations provide the
vital raw material for natural selection, soif the mutation rate is too low
a population will not be able toevolve fast enough to keep up with
environmental changes.
If, on the other hand, a population's mutation rate is too high,detrimental
mutations may accumulate faster than natural selectioncan eliminate them.
Eventually, the number of mutations can exceedthe "error catastrophe
threshold", again leading to the extinctionof a population.
In theory, any species with a very small population could
accumulatedeleterious mutations faster than it can eliminate them. The
problemis especially severe for asexual organisms such as the Amazon mollyan
effect known as Muller's rachet.
It is far less of a problem for sexually reproducing species becausethe
exchange of genetic material between chromosomes can separategood and bad
mutations. Some unlucky offspring get saddled with lotsof nasty mutations
and die out, while the lucky ones get hardly any.
In theory, a mutation catastrophe can also occur as a result oflinkage. This
refers to gene variants that are inherited togetherbecause they sit next to
each other on a chromosome. Suppose amutation that greatly increases the
mutation rate somehow ends upnext to a new mutation that greatly increases
fitness. The immediatefitness benefits of the beneficial mutation will
initially mask thedeleterious effects of the "mutator" mutation, meaning
bothmutations will rapidly sweep through a population, ultimately
withdisastrous consequences.
A few doctors hope to exploit mutation accumulation to treatdiseases.
Certain viruses such as HIV are already close to the errorcatastrophe
threshold. Drugs that increase the mutation rate of theviruses still further
might push them over the threshold and drive apopulation of viruses inside a
person's body to extinction.
Finallly, it has long been recognised that the competition betweenmembers of
the same species to reproduce sexual selection can favourtraits that reduce
a species' overall fitness. Male peacocks withthe biggest and brightest
tails might get the females' attention,but lugging around a heavy,
conspicuous tail reduces their chancesof survival.
Studies of threatened bird species suggest that sexual selection canindeed
drive populations to extinction. Some biologists go so far asto blame sexual
selection for the conspicuous consumption thatthreatens humanity's future.
According to the handicap principle, features such as peacocks'tails evolve
precisely because they are disadvantageous. Consider anindividual who is
trying to signal to females how fit and strong heis. If the signal is easy
to make, weaker males can easily cheat bymaking the same signal. But if
making the signal is costly such asgrowing a large, clumsy tail or giving
away food there's no way tocheat.
Proving that any of these phenomena have ever led to extinctions inthe wild
is far from easy, because any species to which this hashappened are, of
course, no longer around to study. The indirectevidence is growing ever
stronger, though.
Evolution myths: It doesn't matter if people do not understand evolution
At an individual level, it might not matter much. However, anymodern society
which bases major decisions on superstition ratherthan reality is heading
for disaster
So your brother or mother is a creationist. Let them believe whatthey want,
you might think. After all, it makes family get-togethersa lot easier and no
difference to anyone else.
Or does it? Imagine if Mike Huckabee ends up as vice-president ofthe US a
mere heart attack away from the top job. Would you feelcomfortable if the
world's biggest superpower was run by a man whorejects evolution, thanks to
the support of tens of millions ofpeople who also refuse to accept the
truth?
It is dangerous when leaders prefer dogma to biological reality:Stalin's
support for the pseudoscience of Lysenko was a disaster forSoviet
agriculture.
Evolving problems
The success of western civilisation is based on science andtechnology, on
understanding and manipulating the world. Itscontinued success depends on
this, perhaps now more than ever.
Any leader who thinks evolution is a matter of belief is arguablyunfit for
office. How can someone who dismisses the staggeringamount of evidence for
evolution assembled by researchers in myriadfields possibly evaluate more
subtle scientific evidence for, say,climate change?
What's more, evolution is directly relevant to many policydecisions.
Infectious diseases from tuberculosis to wheat rust aremaking a comeback as
they evolve resistance to our defences.Antibiotic-resistant superbugs like
MRSA are a growing problem. Adeadly virus such as H5N1 bird flu or ebola
might evolve the abilityto spread from human to human at any time, leading
to a devastatingpandemic. It is not possible to grasp how serious these
threats areand plan for them unless you understand the power of evolution.
There are many more subtle areas where understanding evolutionmatters too.
For instance, fishing policies that allow fishermen tokeep only large fish
are actually leading to the evolution ofsmaller fish. The tremendous changes
we are making to theenvironment are altering many species, from rats
becoming resistantto poisons to urban birds changing their songs to counter
noisepollution.
There is our future, too. Modern biology is on the brink of givingus
previously unimaginable power over the human body, from reshapingembryos to
rewriting the genetic code and delaying the effects ofageing. Societies'
views on if and how these powers should be usedwill inevitably be shaped by
people's understanding of theirevolutionary origins. Things look rather
different depending whetheryou think we are a perfect, finished product or
crude earlyprototypes thrown up by a desperately cruel process from
whoseclutches we now have to break free.
This is not to say that evolutionary theory tells us how to runsocieties
(see Survival of the fittest justifies everyone forthemselves) or make
ethical decisions (see Accepting evolutionundermines morality). It doesn't.
It is a descriptive science, not aprescriptive one. It does, however, help
us to make informeddecisions.
Evolution myths: 'Survival of the fittest' justifies 'everyone for
themselves'
The "fittest" can be the most loving and selfless, not the mostaggressive
and violent. In any case, what happens in nature does notjustify people
behaving in the same way
The phrase "survival of the fittest", which was coined not by Darwinbut by
the philosopher Herbert Spencer, is widely misunderstood.
For starters, there is a lot more to evolution by natural selectionthan just
the survival of the fittest. There must also be apopulation of replicating
entities and variations between them thataffect fitness variation that must
be heritable. By itself, survivalof the fittest is a dead end. Business
people are especially guiltyof confusing survival of the fittest with
evolution.
What's more, although the phrase conjures up an image of a violentstruggle
for survival, in reality the word "fittest" seldom meansthe strongest or the
most aggressive. On the contrary, it can meananything from the best
camouflaged or the most fecund to thecleverest or the most cooperative.
Forget Rambo, think Einstein orGandhi.
What we see in the wild is not every animal for itself. Cooperationis an
incredibly successful survival strategy. Indeed it has beenthe basis of all
the most dramatic steps in the history of life.Complex cells evolved from
cooperating simple cells. Multicellularorganisms are made up of cooperating
complex cells. Superorganismssuch as bee or ant colonies consist of
cooperating individuals.
Suicidal cells
When cooperation breaks down, the results can be disastrous. Whencells in
our bodies turn rogue, for instance, the result is cancer.So elaborate
mechanisms have evolved to maintain cooperation andsuppress selfishness,
such as cellular "surveillance" programmesthat trigger cell suicide if they
start to turn cancerous.
Looked at from this point of view, the concept of the survival ofthe fittest
could be used to justify socialism rather thanlaissez-faire capitalism. Then
again, the success of social insectscould be used to argue for
totalitarianism. Which illustratesanother point: it is nonsense to appeal to
the "survival of thefittest" to justify any economic or political ideology,
especiallyon the basis that it is "natural".
Is cannibalism fine because polar bears do it? Is killing yourbrother or
sister fine because nestlings of many bird species do it?Is murdering your
children fine because mice sometimes eat their ownpups? Is paedophilia fine
because bonobo adults have sex withjuveniles?
Powerful grip
Just about every kind of behaviour that most of us regard as"unnatural"
turns out to be perfectly natural in some nook or crannyof the animal
kingdom. No one can plausibly argue that thisjustifies humans behaving in
the same way.
Yet even though such examples expose the utter absurdity ofappealing to what
is "natural" to judge right from wrong thenaturalistic fallacy we seem to
have a strange blind spot when itcomes to evolution. Survival of the fittest
has been claimed tojustify all kinds of things, from free markets to
eugenics. Suchnotions still have a powerful grip in some circles.
However, natural selection is simply a description of what happensin the
living world. It does not tell us how we should behave.
Evolution myths: Evolution is limitlessly creative
It might seem like there is no end to nature's inventiveness butthere are
some features that could probably never evolve, at leaston Earth
It often seems that nature invented pretty much everything that canbe
invented long before humans arrived on the scene including thewheel, kind
of. There is a salamander living in the Californianmountains that coils
itself up and rolls downhill when threatened,for example. The pearl moth
caterpillar goes one better and can rollitself along a flat surface for four
or five revolutions to escapepredators.
Nevertheless, there are structures that would clearly be useful buthave
never evolved. Zebras with built-in machine guns would rarelybe bothered by
lions, some point out. So why can evolution inventsome things but not
others?
This is an extremely difficult issue to tackle: how can we studysomething
that has not happened? One way to approach it is to startwith a question
used by those who deny evolution and believe thatmany of nature's
inventions, such as the eye or the bacterialflagellum, are simply too
complex to have evolved. What use is halfa wing, they ask? (see Half a wing
is no use)
Very useful, it turns out. The wings of insects might have evolvedfrom
flapping gills that were originally used for rowing on thesurface of water.
This is an example of exaptation structures andbehaviours that evolved for
one purpose but take on a wholly newone, while remaining useful at every
intermediate stage.
Come in, over
Turn this argument around, however, and it suggests that somefeatures cannot
evolve because a half-way stage really would be ofno use. For example,
two-way radio might be useful for manydifferent animals, for making silent
alarm calls or locating othermembers of your species. So why hasn't it
evolved? The recentinvention of nanoscale radio receivers suggests it is not
physicallyimpossible.
The answer might be that half a radio really is useless. Detectingnatural
radio waves from lightning, for instance would not tellanimals anything
useful about their environment. That means therewill be no selection for
mutations that allow organisms to detectradio waves. Conversely, without any
means of detecting radio waves,emitting them would serve no useful purpose.
Radar might not be ableto evolve for similar reasons.
The contrast with visible light could hardly be greater. It is clearthat
simply detecting the presence or absence of light would beadvantageous in
many environments, that even a blurry picture isbetter than nothing at all,
and so on right up to hawk-eyedsharpness.
Seaweed skies
Emitting visible light can be helpful too, even for creatures thatcannot
detect it themselves. For the bioluminescent phytoplanktonthat light up
ocean waves, for instance, it is a way of summoningpredators that eat the
phytoplankton's enemies. A similar argumentapplies to sound: it is not hard
to see how forms of echolocationevolved independently in groups such as
bats, cave swiftlets andwhales.
One might also wonder why plants that float in the sky like balloonshave
never evolved. The idea does not seem too far-fetched at firstglance: many
seaweeds have floats called pneumatocysts, filled withoxygen or carbon
dioxide. Other algae can produce hydrogen. So filla large, thin pneumatocyst
with hydrogen and perhaps a seaweed couldfly. Flying plants would beat water
and land plants to the light,giving them a big advantage, so why aren't our
skies filled withliving green balloons?
Perhaps partly because large pneumatocysts with extremely thinmembranes
would be far more vulnerable to predators and damage fromwaves, so an
intermediate stage could never evolve. What's more,algae produce hydrogen
only when there's a lack of sulphur in thewater, and in any case the
molecules of hydrogen gas are so tinythat they would leak out of any
pneumatocyst. Half a hydrogenballoon doesn't look very good for anything, at
least on our planet.Even evolution has its limits.
Evolution myths: Natural selection cannot explain homosexuality
There are numerous evolutionary mechanisms that might explainhomosexual
behaviour, which is common in many species of animals
"Simple reasoning shows that evolution cannot explain homosexualityhow would
a homosexuality gene get selected for?" "Why have thegenetic traits
predisposing to homosexuality not been eliminatedlong ago?"
Such arguments are surprisingly common and completely wrong.
Homosexual behaviour has been observed in hundreds of species, frombison to
penguins. It is still not clear to what extenthomosexuality in humans or
other animals is genetic (rather than,say, due to hormonal extremes during
embryonic development), butthere are many mechanisms that could explain why
gene variantslinked to homosexuality are maintained in a population.
A common assumption is that homosexuality means not having children,but this
is not necessarily true, especially in cultures other thanour own. Until it
became acceptable for same-sex couples to livetogether in western countries,
many homosexual people had partnersof the opposite sex. In some traditional
societies, various forms ofnon-exclusive homosexuality were common.
Reasons why
Among animals, homosexual behaviour is usually non-exclusive. Forinstance,
in some populations of Japanese macaques, females preferfemale sexual
partners to male ones but still mate with males theyare bisexual, in other
words.
It has also been suggested that homosexuality boosts
individuals'reproductive success, albeit indirectly. For instance,
same-sexpartners might have a better chance of rising to the top of
socialhierarchies and getting access to the opposite sex. In some
gullspecies, homosexual partnerships might be a response to a shortageof
males rather than have no offspring at all, some female pairsraise offspring
together after mating with a male from a normalmale-female pair.
Another possibility is that homosexuality evolves and persistsbecause it
benefits groups or relatives, rather than individuals. Inbonobos, homosexual
behaviour might have benefits at a group levelby promoting social cohesion.
One study in Samoa found gay mendevote more time to their nieces and
nephews, suggesting it might bean example of kin selection (promoting your
own genes in the bodiesof others).
For your health
Or perhaps homosexuality is neutral, neither reducing nor boostingoverall
fitness. Attempts to find an adaptive explanation forhomosexual behaviour in
macaques have failed, leading to suggestionsthat they do it purely for
pleasure.
Even if homosexuality does reduce reproductive success, as mostpeople
assume, there are plenty of possible reasons why it is socommon. For
instance, gene variants that cause homosexual behaviourmight have other,
beneficial effects such as boosting fertility inwomen, as one recent study
suggests, just as the gene variant forsickle-cell anaemia is maintained
because it reduces the severity ofmalaria. Homosexuality could also be a
result of females preferringmales with certain tendencies sexual selection
can favour traitsthat reduce overall fitness, such as the peacock's tail
(seeEvolution always increases fitness).
Given that, until recently, homosexual behaviour in animals wasignored or
even denied, it's hardly surprising that we cannot yetsay for sure which of
these explanations is correct. It could wellturn out that different
explanations are true in different species.
Related Articles
* Evolution: Survival of the selfless *
http://www.newscientist.com/article.ns?id=mg19626281.500 * 03 November 2007
* Penguins are not people *
http://www.newscientist.com/article.ns?id=mg18825195.900 * 01 October 2005
* Survival of genetic homosexual traits explained *
http://www.newscientist.com/article.ns?id=dn6519 * 13 October 2004 * Queer
creatures * http://www.newscientist.com/article.ns?id=mg16321985.000 * 07
August 1999
Weblinks
* Sexual partner preference in Japanese macaques *
http://dx.doi.org/10.1023/A:1014079117864
Evolution myths: Creationism is an alternative to evolution
The only thing that creationists agree on is that they don't likeevolution.
Even Genesis gives two contradictory accounts of creation
If someone tells you that creationism provides a better explanationfor life
on Earth than the theory of evolution, ask them whichversion of creationism.
Among creationists, there is an extraordinary range of beliefs abouthow life
came to be. A few creationists accept that evolutionproduced the great
diversity of life on Earth apart from humans.Others think all life evolved
but that the process was guided by asupernatural being.
Other creationists accept that evolution can lead to minor
changes(microevolution) but deny that lots of little changes can result
innew species or even new groups of organisms (macroevolution). Somethink a
deity created the very first life but then left it to evolveby itself.
Then there's the vexed issue of timing. "Young Earth Creationists"regard the
Genesis account as "inerrant" despite its contradictions(see Evolution is
wrong because the Bible is inerrant), and claimthe planet was created about
6000 years ago. "Old EarthCreationists" meanwhile accept the hundreds of
lines of evidencesuggesting otherwise.
God, amok
This schism is just the beginning. Some don't dispute the earth'sapparent
age but believe it is an illusion (the omphalos hypothesis,which some
summarise as "God faked it"). Yet others claim that theplanet itself is
billions of years old but that life on it wascreated only recently.
Creationists do at least all believe in a creator. But who is it:God, Allah,
Yahweh, Brahma, Zeus, Olorun, aliens or a gianthermaphrodite?
Those who have studied our planet and the life on it, however, havecome to
very clear conclusions: the Earth is around 4 billion yearsold and all the
life on it gradually evolved from much simplerforms. There is no evidence of
any kind of outside intervention, andno need to invoke it to explain what is
known. Yes, there are manydebates among biologists, geologists and
cosmologists over the finerdetails, but these will be resolved sooner or
later by newdiscoveries or experiments. Reality is the ultimate arbiter.
By contrast, there is no way to resolve the often vast differencesbetween
the numerous forms of creationism. Anyone can come up withtheir own version
of creationism (and many do). How do you convincethe followers of the Flying
Spaghetti Monster, for instance, thathis noodle is not the real creator?
Evolution myths: The theory is wrong because the Bible is 'inerrant'
This argument is undermined by the hundreds of errors andinaccuracies and
contradictions found in Bible. It is anything but"inerrant".
A few creationists are honest enough to admit that the evidencesupporting
the theory of evolution is irrelevant as far as they areconcerned: as it
contradicts the "Word of God", it simply has to bewrong.
Some Christians regard the text of the Bible as literally true or,to use
their term, as "inerrant". If people reject evolution on thisbasis, it is
only fair to ask whether this belief stands up.
Whichever translation of the Bible you look at it is not hard tofind errors.
The texts are full of internal contradictions as wellas historical and
scientific inaccuracies.
There are so many examples it is hard to know where to start. Takeits
cosmology: according to the Bible, the earth is flat andimmovable, the moon
emits its own light, the sky is solid and thestars can be shaken from the
sky by earthquakes.
Its mathematics is also poor. How many sons do you count: "The sonsof
Shemaiah: Huttush, Igal, Bariah, Neriah, and Shaphat, six" (IChronicles
3:22). Such errors are common. The value of pi is givenas 3, even though
many other cultures had already worked it out withgreater precision.
Bible biology
Its biology is no better. The Bible claims that rabbits chew thecud, that
the pattern of goats' coats can be changed by what theirparents look at
while copulating, that only dead seeds can germinateand that ostriches are
careless parents.
So how reliable is the chapter that relates to evolution? Let'sleave aside
the long-standing evidence that Earth is older than 6000years and that there
was no world-wide flood, and look at what elseGenesis says.
Genesis 1 gives the order of creation as plants, animals, man andwoman.
Genesis 2 gives it as man, plants, animals and woman. Genesis1:3-5 says
light was created on the first day, Genesis 1:14-19 saysthe sun was created
on the fourth. Genesis 7:2 says Noah took sevenpairs of each beast, Genesis
7:8-15 says one pair.
The list goes on. The fruit of the tree of knowledge is said to killwithin a
day of being eaten, yet Adam and Eve don't die after eatingit. Genesis says
there were giants (Nephilim) before the flood andthat the flood annihilated
all creatures other than those on theark, but Numbers says there were giants
after the flood.
Sorting it out
Attempts to resolve these contradictions are almost as old as theBible
itself. Those who regard the Bible as inerrant tie themselvesin knots trying
to explain them away (hands up who believes that T.rex was once a peaceful
vegetarian?), or even take it uponthemselves to rewrite the Bible to expunge
them.
However, there are far too many errors, inaccuracies andcontradictions to
dismiss them all. The only rational and reasonableconclusion is that the
Bible is not inerrant.
Don't believe us? That's OK. Go look up all these examples foryourself, ask
questions and make up your own mind.
Evolution myths: Accepting evolution undermines morality
Actually people in more secular countries appear to behave moremorally. And
even if this claim was true, that would not alter thefacts or justify their
suppression.
"Darwinism claims that living beings have evolved as a result ofcoincidences
and by means of a struggle for life. This evil moralityadvises people to be
egoistical, self-seeking, cruel andoppressive."
Such views are not uncommon. The unspoken implication is either
that"Darwinism" (see Biologists are Darwinists) is wrong because itleads to
immorality, or that this knowledge should be suppressedeven though it is
true. Both are nonsense. Even if it were true thataccepting the theory of
evolution undermined people's sense ofmorality, it is not a reason to doubt
the reality of evolution. Thisis equivalent to arguing that atomic theory
must be wrong because anuclear war would be catastrophic.
It is also simply not true that evolution undermines morality.Certainly
there are examples of people appealing to evolutionaryideas to justify
behaviour some would regard as immoral, althoughthe best example one
creationist could find was a song called TheBad Touch by the Bloodhound
Gang, with its chorus: "You and me babyain't nothin' but mammals. So let's
do it like they do on theDiscovery Channel."
On the other hand, one could draw up an extremely long list ofexamples of
people appealing to religion to justify immoralbehaviour, from slavery and
racism to suicide bombings and genocide.This kind of exercise proves little,
though.
Rational morality
A better way of assessing the effects of embracing evolution is tocompare
countries with different levels of acceptance. Countrieswhere higher numbers
of people accept evolution have lower rates ofmurders, sexually transmitted
diseases, teenage pregnancies and soon. In fact, more secular societies are
healthier in almost everyregard, one 2005 study (pdf) concluded.
This kind of crude correlation does not prove accepting evolutionactually
promotes moral behaviour, nor that religion promotesimmoral behaviour.
Indeed, other studies suggest the issue is farmore complex. But it does
prove accepting evolution does notimmediately lead to the breakdown of
society, as some creationistsclaim.
Those who dismiss evolution as immoral often assume that religion iscrucial
to morality. As in: "People who believe in evolution have nobasis for a
moral code, other than the preeminent concern to pass onone's genetic
inheritance."
In fact, there is growing evidence that we have an innate moralsense that
morality is something that evolved, in other words. Thismay seem surprising
to those for whom the phrase "survival of thefittest" conjures up images of
lions ripping each other to shredsand stags clashing antlers. But "the
fittest" can mean thecleverest, the sneakiest, the best camouflaged, the
leastaggressive, the most attractive or the least selfish.
Natural selection can favour altruism and fair play in certaincircumstances.
Behaviours such as loyalty to kin, intolerance oftheft and punishment of
cheats the roots of morality can be seen inmany of our primate cousins.
Evolution myths: Evolutionary theory leads to racism and genocide
Darwin's ideas have been invoked as justification for all sorts ofpolicies,
including some very unpleasant ones. But evolutionarytheory is a descriptive
science. It cannot tell us what is right andwrong.
Rather than attack evolution directly, some try to tar it byassociation. The
claim is often made that the theory of evolutionleads inevitably to eugenics
and to atrocities like thoseperpetrated by Hitler. These claims are
irrelevant to the reality ofevolution and are also largely untrue.
Let's start with Darwin himself, who is often accused of being aracist and a
eugenicist. Yet Darwin went very much against the ideasof his time by
dismissing some of the perceived differences betweenraces. For instance:
"...this fact can only be accounted for by thevarious races having similar
inventive or mental powers."
The following passage is often quoted by those who accuse him ofsupporting
eugenics: "It is surprising how soon a want of care, orcare wrongly
directed, leads to the degeneration of a domestic race;but excepting in the
case of man himself, hardly any one is soignorant as to allow his worst
animals to breed."
The next few paragraphs are often left out: "...If we were tointentionally
neglect the weak and the helpless, it could only befor a contingent benefit,
with overwhelming present evil. Hence wemust bear without complaining the
undoubtedly bad effects of theweak surviving and propagating their kind..."
Eugenical Christians
There is no doubt that some of those who supported eugenics citedDarwin's
theory of evolution as inspiration or justification, butthen evolution has
been invoked to support all kinds of notions andschemes, from communism to
capitalism.
Biology tells us what is, not what ought to be. It is descriptive,not
prescriptive or normative. It can inform our decisions bytelling us what the
likely outcome of different actions will be, butnot which of these outcomes
are ethical or desirable.
In retrospect, it is clear that many of the eugenic policiesimplemented in
the early 20th century were based as much if not moreon racial and social
prejudices than on any understanding ofgenetics and evolution. Some may have
used evolutionary theory as anexcuse, but that does not make it the cause.
What's more, many of the most enthusiastic promoters of the eugenicsmovement
in the US, which led to policies such as compulsorysterilisation, were
evangelical Christians. As Mary Teats explainedin her book The Way of God in
Marriage: "The great and rapidlyincreasing army of idiots, insane,
imbeciles, blind, deaf-mutes,epileptics, paralytics, the murderers, thieves,
drunkards and moralperverts are very poor material with which to 'subdue the
world',and usher in the glad day when 'all shall know the Lord'."
As for the Holocaust, the murder of able-bodied and able-mindedpeople solely
on the basis of their religion can hardly be calledeugenics. It is
incredible to blame Darwin while overlooking therole of Christianity in
fostering anti-Semitism over the centuries.
In 1543, for instance, Martin Luther wrote a booklet called On theJews and
Their Lies calling, among other things, for Jews to beexpelled or forced to
do manual labour, and their synagogues andschools burned. The booklet was
displayed at Nazi rallies. And thisis how Hitler described his motivations
in Mein Kampf, in whichthere is no mention of Darwin or the theory of
evolution: "Hencetoday I believe that I am acting in accordance with the
will of theAlmighty Creator: by defending myself against the Jew, I am
fightingfor the work of the Lord."
Evolution myths: Religion and evolution are incompatible
There are various ways in which the known facts about evolution canbe
reconciled with theistic religions. Some of these ways might beillogical and
irrational, but they are no more illogical andirrational than other aspects
of religions.
The biologist Stephen Jay Gould argued that there is no conflictbetween
science and religion: "Science tries to document the factualcharacter of the
natural world, and to develop theories thatcoordinate and explain those
facts. Religion, on the other hand,operates in the equally important, but
utterly different, realm ofhuman purposes, meanings, and values."
This line is popular with those who wish to avoid confrontation.Most people,
however, see both science and religion as makingfactual claims about the
natural world, and no scientific facts areharder to reconcile with religious
claims than those of evolution.Almost all the major religions are divided on
the issue, with somesects, priests or scholars accepting it as reality and
othersrejecting it.
Needless to say, evolution is incompatible with a literalinterpretation of
the creation myths that form part of manyreligious texts, such as Genesis
(see Evolution is wrong because theBible is inerrant). Of the major
religions, only Buddhism escapesthis fundamental conflict: its founder is
said to have refused toanswer questions about the origin of life.
God steps in
Polls suggest many people in western countries who believe in asupernatural
being accept that evolution happened but believe itscourse was somehow
influenced by that being.
In the absence of a time machine that would allow us to observeevery step in
the evolution of humans, the possibility that somedeity or alien intervened
in the process cannot be ruled out.
However, this "god of the gaps" argument is the logical equivalentof
standing on a beach pointing to missing sections in a trail offootprints and
claiming the creator must have flown between the gapseven as incoming waves
create more gaps in the trail, and even asthe ordinary-looking person who
made the footprints can be seenwalking along in the distance.
Even without that time machine, we are starting to identify many ofthe
mutations that made us human, such as ones related to learning,speech and
brain size, and there is nothing supernatural about them.As more and more
genomes are sequenced, and more fossils unearthed,we will be able to fill in
ever more of the details.
In the beginning
What about a being who set evolution in motion but didn't interferein the
process? This is how the geneticist Francis Collins sees it:"At the moment
of the creation of the universe, God could also haveactivated evolution,
with full knowledge of how it would turn out."Others take this further,
suggesting that while the universe wasdesigned to ensure some kind of
intelligent life evolved, theresults of evolution were not entirely
predestined.
The "deity who set evolution in motion but didn't interfere"interpretation
avoids any conflict with the established facts ofevolution, but it also
raises some tricky questions. For instance,why would a caring deity choose
to "create" through such a cruelprocess? If animals don't have "souls", at
what point did earlyhumans acquire them?
Finally, some people regard "God" not as a conscious being whostands outside
the universe and intervenes in it, but more as thedivine present in all
things. In this view, God is nature. Suchpantheistic ideas have been
suggested by adherents of all the majorreligions over the ages.
So are religion and evolution incompatible? It depends who'sjudging. The
idea that many religious people find most satisfactorythat a deity
intervened in and directed the evolutionary processcannot be disproved but
is not supported by any evidence. Theinterpretations that are most
compatible with what we know that Goddid not intervene in evolution after
creating the universe, or Godis nature are ones that many believers find
unpalatable.
Of course, some biologists such as Richard Dawkins and PZ Myers arewell
known for dismissing all theistic religions. However, thequestion of whether
religion and evolution are compatible is not thesame as the bigger question
of whether any theistic religion iscompatible with reason and rationality.
Evolution myths: Half a wing is no use
Just as objects designed for one purpose can be used for another, sogenes,
structures and behaviours that evolve for one purpose becomeadapted to do
another
Ever used a newspaper to light fires or mop up spills? Stood on achair to
reach something? Or swatted flies with a rolled-up copy ofNew Scientist?
Just as objects designed for a specific purpose canbe co-opted for something
quite different, so features that evolvedto do one task can be used for
another and often are.
But what use is half a wing? It's a question that those who doubtevolution
first asked more than a century ago. When it comes toinsects, rowing and
skimming could be the answer. Stonefly nymphshave flapping gills for
extracting oxygen from water. When standingon the water's surface, early
insects could have used these gillsfor getting oxygen and propulsion rowing
simultaneously. Somestoneflies still stand on the surface and "row" across
water usingtheir wings.
Over time, flapping could have replaced rowing as the main means
ofpropulsion, allowing insects to skim across the water's surface: lowlevels
of friction on this scale mean proto-wings would not have hadto generate
much air flow to be useful for skimming.
As these proto-wings became more efficient and specialised, earlyinsects may
have taken further steps towards flying. While someskimming insects keep all
six legs on the water's surface, fasterskimmers keep just four legs or two
legs on the water. Thissurface-skimming hypothesis concerning the evolution
of insectflight shows how flapping gills could gradually have turned
intowings while remained useful at every stage.
> From T-rex to sparrow
What about the wings of birds? In some dinosaurs, the scalescovering their
bodies evolved into hair-like feathers, most likelyto insulate warm-blooded
bodies or help keep eggs warm.
Those dinosaurs with feathers on their limbs might then have startedto
exploit the aerodynamic properties offered by feathers, perhapsgliding
between trees or running faster along the ground. Fossilsshow a gradual
transition from downy, hair-like feathers into therigid flight feathers that
form the key part of birds' wings.
Another idea that is gaining favour is that flapping forelimbshelped the
ancestors of birds to run up steep slopes or climb treesa technique many
birds still employ today.
Without a time machine it is difficult to prove exactly what earlybirds or
insects used "half a wing" for. But it is now clear thathalf a wing can have
all sorts of uses. Indeed, there are numerousexamples of physical structures
and behaviours that evolved for onepurpose acquiring another one, a process
called exaptation.
Reuse recycle
Evo-devo evolutionary developmental biology is even starting toidentify the
precise mutations that underlie such changes. Forinstance, the forelimbs of
the ancestor of bats turned into wingspartly thanks to a change in a gene
called BMP2 that made its"fingers" far longer than normal.
The webbing between the extra long digits that makes up the bat wingis a
reappearance of a long-lost feature: as embryos, all tetrapodsinitially
develop webbed digits, a hangover from our fish ancestors.Normally, this
webbing kills itself off at an early stage, but inbats this cell suicide is
blocked.
Repurposing a structure does not have to involve the loss of theoriginal
structure. Reptilian jaw bones turned into mammalian earbones, without the
loss of the jaw. The neural circuitry that allowsus to make fine limb
movements may have been adapted to producespeech as well.
In fact, almost every feature of complex organisms can be seen as avariation
on a theme. Switching off one gene in fruit flies, forinstance, can turn
their antennae into legs.
On the shoulders of fish
Sometimes just one aspect of a feature can be co-opted for anotheruse. The
first hard mineralised structures to evolve in ourancestors were the teeth
of early fishes known as conodonts. Oncethe ability to form hard
hydroxyapatite had evolved, it could beexploited elsewhere in the body and
may have been the basis of thebony skeletons of all vertebrates.
As these examples show, there are all kinds of routes by whichstructures and
behaviours that evolved for one purpose cancontribute to new structures and
abilities. Just because it is notimmediately obvious how something as
complex as a bacterialflagellum evolved (see The bacterial flagellum is
irreduciblycomplex) does not prove it did not evolve.
An even more interesting question than what half a wing is good foris
whether some features cannot evolve because half of them reallywould be
useless. Such thought experiments might not prove anythingbut they can be
fun (see Evolution is limitlessly creative).
Evolution myths: Evolution is not predictive
It might not be possible to predict exactly what life will look likein a
billion years but what counts are the predictions that can bemade
Cosmologists make precise predictions about what will happen to theuniverse
in 20 billion years' time. Biologists struggle to predicthow a few bacteria
in a dish might evolve over 20 hours. Some claimthat this lack of precise
predictive power means evolution is notscientific.
However, what matters in science is not how much you can predict onthe basis
of a theory or how precise those predictions are, butwhether the predictions
you can make turn out to be right.Meteorologists don't reject chaos theory
because it tells them it isimpossible to predict the weather 100% accurately
on the contrary,they accept it because weather follows the broad patterns
predictedby chaos theory.
The difficulty in predicting the course of evolution arises partlybecause
organisms are free to evolve in quite different directions.The descendants
of a single species of ape living in Africa around 6million years ago, for
instance, ended up taking rather differentpaths; those that eventually led
to gorillas, chimpanzees andhumans. Such splits in populations might stem
from tiny initialvariations.
The evolutionary paths these apes took might also have beeninfluenced by
changes in the climate. As this shows, the history oflife on this planet has
been partly shaped by chance events. If anasteroid hadn't wiped out the
dinosaurs, the first intelligent lifeform might have been very different, if
indeed human-likeintelligence had evolved at all. If we could wind the clock
back 4billion years and let life evolve all over again, its course mightbe
very different.
Old age planet
Nevertheless, although evolution's predictive power might appearlimited, the
theory can be and is used to make predictions at allsorts of levels. Darwin
realised that the Earth must be very old forthere to have been enough time
for all the life on it to evolve. Ithas turned out to be even older than he
thought.
He also predicted that transitional fossils would be discovered, andmillions
(trillions if you count microfossils) have been.Researchers have even been
able to predict the age and kind of rocksin which certain transitional
fossils should occur, as with thehalf-fish, half-amphibian Tiktaalik.
Or take the famous peppered moth, which evolved black colouration toadapt to
pollution-stained trees during industrialisation inBritain. Remove the
pollution and the light strain should once againpredominate, which is just
what is happening.
Bugged by bugs
Perhaps the most striking prediction in biology was made in 1975
byentomologist Richard Alexander. After studying the evolution ofeusocial
insects such as termites, he predicted that some burrowingrodents in the
tropics might have evolved the same eusocial systemas later proved to be the
case with the naked mole-rat.
Evolutionary theory can and increasingly is being put to morepractical use.
For instance, if you genetically engineer crops toproduce a pesticide, it is
clear that resistant insect strains arelikely to evolve. What is less
obvious is that you can slow thisprocess by growing regular plants alongside
the GM ones, as waspredicted and has turned out to be the case.
Many researchers developing treatments for infectious diseases nowtry to
consider how resistance could evolve and find ways to preventit, for
instance by giving certain drugs in combination. This slowsthe evolution of
resistance because pathogens have to acquireseveral mutations to survive the
treatment.
Most predictions relate to very specific aspects of evolutionarytheory. If a
eusocial mammal like the naked mole-rat had not beenfound, for instance, it
would have proved only that Alexander'sideas about the evolution of eusocial
behaviour were probably wrong,not that there is anything wrong with the
wider theory. However,some broad predictions including the age of Earth, the
existence oftransitional fossils and the common origin of life are crucial
testsof the basic theory (see Evolution cannot be disproved).
Evolution myths: Evolution cannot be disproved
There are all sorts of findings and experiments that could havefalsified
evolution. In the century-and-a-half since Darwinpublished his theory, not
one has
To count as science, hypotheses and theories should make predictionsthat
might turn out to be wrong. In other words, it should bepossible to falsify
these ideas. Some claim this is not true ofevolution, but this is simply
because we find it hard to imagine howdifferent life might have been if it
had not evolved.
When asked what would disprove evolution, the biologist J. B. S.Haldane
reportedly growled: "Fossil rabbits in the Precambrian".What he meant is
that the progression over time seen in the millionsof fossils unearthed
around the world is exactly what evolutionarytheory predicts.
Unicellular organisms, for example, appear before multicellularones. Jawless
fish precede jawed fish. Lunged fish precedeamphibians. Amphibians precede
reptiles. Reptiles with scalesprecede mammals and birds with modified scales
(fur and feathers).Apes precede humans. All it would take is one or two
exceptions toseriously challenge the theory.
Fraudulent claims
Clearly if the first fossil amphibians were older than the firstfossil fish,
it would show that amphibians could not have evolvedfrom fish. No such
exceptions have ever been found anywhere. Therehave been a few claims to
this effect, of course, but even mostcreationists admit that these claims
are fraudulent.
Rabbits with feathers could also disprove evolution. There areanimals with a
mixture of mammalian and reptilian features, such asechidnas, and there are
fossils with a mixture of bird and reptilianfeatures, such as the toothy
archaeopteryx. However, no animals havea mixture of mammalian and bird
features.
This is just what would be expected if birds and mammals evolvedfrom
separate groups of reptiles. There is no reason why an"intelligent designer"
would not have mixed up features, such ascreating mammals with feathers and
efficient bird-like lungs, orfurry, breast-feeding ostriches.
Furthermore, if all organisms were created to fulfil particularroles, they
might be unable to evolve. Instead countlessexperiments, both planned and
unplanned, show that organisms of allkinds evolve and adapt to changing
conditions, providing the changesare not too abrupt. The breeding of plants
and animals, orartificial selection, has produced an incredible range of
forms injust a few thousand years, such as turning wolves into chihuahuasand
great danes. In the laboratory, researchers have been able toproduce
bacteria, plants and animals with all kinds of novelcharacteristics. They
have even produced entirely new species .
In the wild, too, there are numerous examples of evolution inaction. Many
viruses and bacteria have changed dramatically in thespace of a human
lifetime, from HIV adapting to humans to H5N1 birdflu. Several fish species
are becoming smaller, thanks to theselection pressure exerted by humans
catching all the large fish.Weeds like Crepis sancta are adapting to cities
by changing theirseeds.
Deep time
If Earth was very young, that would also be a problem for evolution,because
evolution by natural selection requires vast stretches oftime "deep time" as
Darwin realised. Some thought evolution had beenfalsified in the 19th
century, when physicist Lord Kelvin calculatedthat the Earth was just 30
million years old. Thats far younger thanDarwins 300-million-year estimate,
which Darwin based on how long itwould have taken to erode a rock formation
called the Weald in theUK. But both were wrong. Several lines of evidence,
including leadisotopes, show that Earth is far older than even Darwin
imagined:about 4 billion years.
Darwin also proposed that all life has descended from a commonancestor. This
idea, originally based on studies of anatomy anddevelopment, is being
confirmed by genome sequencing. All life onEarth has turned out to work in
essentially the same way: organismsstore and translate information using the
same code, with only a fewminor variations between the most primitive
organisms. Huge chunksof this information are identical or differ only
slightly evenbetween species that appear very different. Some key
developmentalgenes in the fly can be replaced by the mouse versions without
anyill effect, for instance.
No foresight
Had life been designed, though, even organisms that look similarcould have
turned out to have very different inner workings, just asan LCD screen has a
quite different mechanism to a plasma screen.Human designers are already
creating a range of new life forms whosemolecular underpinnings will be very
different from those ofexisting life forms.
Some argue that it would have made sense for a "designer" to makeall species
variations on the same theme, but wouldn't this applyonly to a designer with
limited resources or imagination? Anall-powerful creator could have made a
world in which every singlespecies was entirely unique and unrelated to any
other.
You also might expect the work of a creator to be easy for us tospot
evidence for, just as Craig Venter has "signed" the syntheticbacterial
genome he created. Instead, the bodies and genomes ofcomplex creatures
reveal a total lack of any intelligence orforesight.
Most of our DNA for instance, consists of millions of defunct copiesof
parasitic DNA. Our bodies are riddled with obvious "design"flaws, from the
blind spot in the eye to the bizarre meandering pathof our vagus nerve.
Furthermore, the high rate of mutations inhumans make it inevitable that
some people will be born with awfulgenetic diseases such as cystic fibrosis
or Huntington's. Theinescapable conclusion is that if indeed life were
designed, thedesigner was lazy and incompetent at best, or cruel at worst.
Evolution myths: Evolution is just so unlikely
By weeding out harmful mutations and assembling beneficial ones,natural
selection acts like an "improbability drive" that can, givenenough time,
produce results that appear utterly impossible at firstglance
In a recent TV special shown in the UK, called The System, a motherwith big
debts was persuaded to borrow even more money to bet on ahorse race. Having
been sent correct predictions of six previousraces, she believed illusionist
Derren Brown really had come up witha foolproof system for predicting the
outcome of races.
In fact, the producers of the show started by sending differentpredictions
to nearly 8000 people. After each race, those sentpredictions that turned
out to be wrong were eliminated and anotherset of varying predictions sent
to the remaining participants. Whatappears utterly extraordinary at first
sending someone correctpredictions of the winners of six races seems very
ordinary as soonas you understand that thousands of people got wrong
predictions.
Confronted by the marvels of the living world, many people jump tothe same
conclusion to the woman in the programme: they cannot bethe result of chance
alone. But what we dont see are all thefailures: the countless numbers of
creatures that died in the egg orin the womb, or hatched or were born with
terrible defects, or fellvictim to predators or disease because of some
weakness.
In the wild, most individuals die long before they get a chance toreproduce.
The living organisms on Earth are the result not just ofsix rounds of
selection, as in the TV programme, but of trillions.This, not chance, is the
crucial factor in evolution.
Three steps to evolution
To understand evolution, you need to appreciate three things.Firstly, that
quadrillion-to-one chances actually happen all thetime. Secondly that, while
mutation is random, which mutationssurvive often is not. And thirdly, given
enough time, theaccumulation of one beneficial mutation after another can
produceamazingly complex systems. Natural selection can be seen as a kindof
improbability drive that given enough time makes the apparentlyimpossible
extremely likely.
If you pick even the simplest creatures alive today and calculatethe odds of
getting their genome by randomly shuffling DNAsequences, you'll find they
are pretty astronomical. Even matchingthe sequence of the simplest virus is
stupendously unlikely.
Does this prove evolution is impossible? Try this: get a pack ofcards,
shuffle it well and spread it out so you can see thesequence. Now try to
generate the same sequence by shuffling anotherpack.
Done it yet? The universe might end before you succeed. If shufflesare truly
random, the chance of generating any particular sequenceof 52 cards is 1
followed by 68 zeroes and yet such an incrediblyunlikely event happens each
time any pack is shuffled.
Shifting genes
In all living creatures, the "pack of cards" is constantly beingshuffled.
Damage to DNA or mistakes in replicating it generaterandom mutations,
ranging from changes in single "letters" toduplications or deletions of huge
chunks of DNA. The vast majoritywill be either harmful or neutral - only a
few will be beneficial.But as the card example shows, even if all beneficial
mutations arehighly unlikely, this doesn't mean they cannot happen.
In fact, the odds of a beneficial mutation occurring are higher thanyou
might think. One recent study of the E. coli gut bacterium putsthe rate as
high as 1 beneficial mutation for every 10,000 newbacteria.
That might not sound like much but populations of many simpleorganisms can
number in the trillions, with new generationsappearing every hour or less.
Do the sums.
What really matters, though, is what happens after mutations appear.That's
when natural selection kicks in. Each new organism's life isessentially a
rigorous testing process. Those with a harmfulmutation will tend to die out,
while those with a beneficialmutation that gives them a competitive edge
will thrive and producemore descendants. This means that beneficial
mutations will becomemore common in a population, while harmful mutations
disappear.
This process happens over and over again. If individuals with onebeneficial
mutation thrive and multiply, eventually anotherbeneficial mutation will
occur in one of them. Over time individualswith both beneficial mutations
will come to dominate a population,making it likely for yet another
beneficial mutation to appear inone of them...
Benefits of sex
What's more, in species that can swap genetic material, for instanceby
reproducing sexually, beneficial mutations that occur in separateindividuals
can be combined in their descendants. In this way,natural selection can
create the astonishing organisms we see aroundus, the result of countless
trillions of beneficial mutations slowlyassembled over billions of years
(see Mutations can only destroyinformation).
It's true that how the process got underway in the first place isstill
something of a mystery. We won't begin to know just how likelyor unlikely
the origin of life was until someone manages to get lifeto evolve from
scratch in the lab or discovers life that originatedindependently, perhaps
on another planet. What is clear, however, isthat as soon as the first
primitive entities capable of replicatingthemselves emerged, further
evolution was inevitable.
And the more evolution there is, the faster it may become. In fact,evolution
might produce "evolvability". For instance, as organismsevolve systems that
can cope with a wide range of environmentalconditions, further evolution
might become more feasible an ideabacked by recent experiments showing
evolution can be speeded byvarying the environment.
Such ideas remain controversial. What is indisputable is that whilethe end
results of evolution might appear utterly impossible, onceyou understand the
way in which natural selection can collect anddistil the results of chance
events, there's nothing impossibleabout it at all.
Evolution myths: Evolution is random
No and yes. Natural selection is a rigorous testing process thatfilters out
what works from what doesnt, driving organisms to evolvein particular
directions. However, chance events play a big roletoo.
"The chances that life just occurred are about as unlikely as atyphoon
blowing through a junkyard and constructing a Boeing 747,"astronomer Chandra
Wickramasinghe told a court in Arkansas in 1981,according a report in New
Scientist (21 January 1982, p 140). Hiscolleague Fred Hoyle made the tornado
version of this claim famousproving that even very clever people can utterly
misunderstandevolution.
A somewhat better analogy would be starting with a millionjunkyards,
painstakingly testing the wreckage left in each one afterthe tornado to find
the most flight worthy, making a million exactcopies of that junkyard,
unleashing another million tornadoes,running another series of exhaustive
tests, and so on, until youproduce some kind of machine no matter how crude
andun-Boeing-747-like capable of flying at least a few yards.
Promoting survival
Evolution by natural selection is a two-step process, and only thefirst step
is random: mutations are chance events, but theirsurvival is often anything
but. Natural selection favours mutationsthat provide some advantage (see
Evolution promotes the survival ofspecies), and the physical world imposes
very strict limits on whatworks and what doesn't. The result is that
organisms evolve inparticular directions.
Consider any kind of creature that lives underwater and has to chaseits
prey, for instance. Random mutations will result in someoffspring having
variety of shapes. Those with shapes that allowthem to move faster with less
energy are much more like to surviveand reproduce than those whose shapes
slow them down.
The result is that all fast-swimming creatures evolve a streamlinedshape, as
we see in animals as diverse as squid, sharks anddolphins. It might look
like the result of design, but it showsinstead the power of natural
selection, which can be thought of as arigorous real-world testing process
for evaluating the effect ofdifferent mutations.
Mutation boost?
Organisms do not always hang about waiting for a helpful mutation tooccur.
For instance, the parasite that causes sleeping sickness hasthousands of
spare genes for its coat proteins, which it mixes andmatches to generate new
coats faster than its host's immune systemcan keep up.
More controversially, a few biologists think some microbes may haveevolved
mechanisms for boosting the mutation rate in specific geneswhen they are
struggling to cope with a changing environment, or for"storing up" variation
for when it is needed. Even if suchmechanisms do exist, however, all they do
is produce randomvariation. Natural selection the testing process is what
movesevolution in particular directions.
One consequence of this is that evolution tends to produce similar"designs"
to meet similar problems, a phenomenon known asconvergence. There are
countless examples. Pterosaurs, birds andbats all evolved similar ways of
flying. Tuna and some sharks usesimilar mechanisms to keep their swimming
muscles warmer than thesurrounding water.
A resemblance
Evolutionary convergence occurs at every level, from proteins tosocieties.
An unusual antibody once thought to be unique to camelshas a close
equivalent in sharks, for instance, while naked molerats form social
colonies like those of ants and bees.
What this means is that if we could wind the clock back and let lifeevolve
all over again, life might take very different paths butstill produce
organisms that, in some ways, resemble the organismsalive today.
There would almost certainly be streamlined swimmers in the oceansand winged
creatures in the skies. In fact, some argue that theevolution of
intelligence is also virtually inevitable, thoughintelligent organisms could
be very different from us.
Taking a different route
Although evolution is not random in the sense described above,chance still
plays a huge role. There are often numerous possibledirections in which
evolution can go. Take the finches Darwincollected from the Galapagos
Islands, which had diverged into 13separate species with beaks specialised
for different foods. Why onegroup of birds took one route and not another
probably dependedentirely on chance mutations, in particular individuals,
thataffected beak size and shape.
What's more, some mutations spread through a population or die outbecause of
random genetic drift rather than natural selection (seeNatural selection is
the only means of evolution). And chance eventsplay a huge part too: if a
huge asteroid hadn't struck the Earth 60million years ago, dinosaurs might
still rule the Earth.
So, while it's wrong to think that evolutionary theory implies
thatstructures such as the eye and wing arose by accident, ichance doesplay
a role in evolution.
Evolution myths: Mutations can only destroy information
Biologists are uncovering thousands of examples of how mutationslead to new
traits and even new species. This claim not only fliesin the face of the
evidence, it is also a logical impossibility
Most people lose the ability to digest milk by their teens. A fewthousand
years ago, however, after the domestication of cattle,several groups of
people in Europe and Africa independently acquiredmutations that allow them
to continue digesting milk into adulthood.Genetic studies show there has
been very strong selection for thesemutations, so they were clearly very
beneficial.
Most biologists would see this as a gain in information: a change
inenvironment (the availability of cow's milk as food) is reflected bya
genetic mutation that lets people exploit that change (gaining theability to
digest milk as an adult). Creationists, however, dismissthis as a
malfunction, as the loss of the ability to switch off theproduction of the
milk-digesting enzyme after childhood.
Rather than get bogged down trying to define what information is,let's just
look at a few other discoveries made by biologists inrecent years. For
instance, it has been shown a simple change ingene activity in sea squirts
can turn their one-chambered heart intoa working two-chambered one. Surely
this counts as increasinginformation?
TRIMming the genome
Some monkeys have a mutation in a protein called TRIM5 that resultsin a
piece of another, defunct protein being tacked onto TRIM5. Theresult is a
hybrid protein called TRIM5-CypA, which can protectcells from infection with
retroviruses such as HIV. Here, a singlemutation has resulted in a new
protein with a new and potentiallyvital function. New protein, new function,
new information.
Although such an event might seem highly unlikely, it turns out thatthe
TRIM5-CypA protein has evolved independently in two separategroups of
monkeys. In general, though, the evolution of a new geneusually involves far
more than one mutation. The most common way fora new gene to evolve is for
an existing gene to be duplicated. Oncethere are two or more copies, each
can evolve in separatedirections.
The duplication of genes or even entire genomes is turning out to
beubiquitous. Without a duplication of the entire genome in theancestor of
modern-day brewer's yeast, for instance, there would beno wine or beer. It
is becoming clear that every one of us has extracopies of some genes, a
phenomenon called copy number variation.
The evolution of more complex body plans appears to have been atleast partly
a result of repeated duplications of the Hox genes thatplay a fundamental
role in embryonic development. Biologists areslowly working out how
successive mutations turned a pair ofprotoHox genes in the simple ancestors
of jellyfish and anemonesinto the 39 Hox genes of more complex mammals.
Newly minted
Can mutation really lead to the evolution of new species?
Yes. Several species of abalone shellfish have evolved due tomutations in
the protein "key" on the surface of sperm that binds toa "lock" on the
surface of eggs. This might appear impossible, butit turns out that some
eggs are prepared to be penetrated by deviantsperm. The same thing can
happen in fruit flies, and likely in manyother groups too. In yeasts, the
mutations that led to some newspecies forming have not only been identified,
they have even beenreversed.
The list of examples could go on and on, but consider this. Mostmutations
can be reversed by subsequent mutations a DNA base can beturned from an A to
a G and then back to an A again, for instance.In fact, reverse mutation or
"reversion" is common. For any mutationthat results in a loss of
information, logically, the reversemutation must result in its gain. So the
claim that mutationsdestroy information but cannot create it not only defies
theevidence, it also defies logic.
Evolution myths: All biologists are Darwinists
Modern evolutionary theory is built on some - but not all - ofDarwin's
ideas, but has gone far beyond them
It is often assumed that biologists eagerly embraced Darwin's theoryabout
the origin of species when he unveiled it, and that scientistscontinue to
accept all his ideas to this day.
In fact, various ideas about the evolution of life had been aroundlong
before Darwin came up with his theory. It was the compellingevidence that
Darwin assembled in his 1859 book On the Origin ofSpecies, however, that
really convinced most biologists of theevolution of life by descent with
modification from a commonancestor.
Modern biologists see Darwin's greatest contribution as the mainmechanism he
proposed: natural selection. During Darwin's lifetime,however, many
biologists were not convinced that it could accountfor evolution, and the
idea fell out of favour.
In the 1930s, it was revived by population biologists, who provedthat
natural selection is a very powerful force driving evolutionarychange (but
not the only one). And with the development of genetics,biologists began to
discover exactly how evolution takes place. Thisled to a new understanding
of evolution, based on discoveries inmany different fields, called the
modern synthesis.
Modern evolution
In many ways the modern synthesis is an extension and refinement ofDarwin's
ideas, but there are also some important differences. Inparticular, some
evolution is now attributed to genetic drift.
While Darwin was right about most things, he also made a fair fewmistakes.
The biggest was his hypothesis of "pangenesis", describedin detail in his
1868 book The Variation of Animals and Plants UnderDomestication. According
to this theory, beneficial characteristicsacquired during the life of an
organism could be passed ontooffspring over the course of several
generations, thanks toparticles called "gemmules" shed by body cells that
becameconcentrated in the reproductive organs.
Darwin thought this could explain, for instance, why children areborn with
thicker skin on the soles of their feet than elsewhere,but this idea was
dismissed in the 20th century. There's a twist inthis tale, though: a few
biologists now think there might be waysfor traits acquired during an
organism's lifetime to be passed on.However, it has yet to be proved that
this can happen and, even ifit can, it is very much the exception rather
than the norm.
Darwin's other mistakes are more trivial. For instance, in oneedition of
Origin of Species, Darwin enthused about "Eozooncanadense", which had been
identified as a primordial microorganismby others but whose "fossils" turned
out to be nothing more thanmineral formations.
Darwin also thought the dog was a hybrid of several wild ancestorswhereas
chickens had only one ancestor. Actually, it turns out thethe opposite is
true. He also suggested the lung evolved from theswimbladder of fish,
whereas nowadays it appears the reverse istrue.
Some biologists are now calling for a revision of the modernsynthesis to
take into account of how new findings have changed ourview of, for instance,
the nature of genes, the origin of sex,epigenetic inheritance, levels of
selection and speciation. Such arevision, however, would merely formally
recognise what biologistshave already learned in recent decades.
So what have they learned? In a sentence, that while the concept ofevolution
by natural selection proposed by Darwin was simple, overthe Earth's
4-billion-year history it has led to incredibly complexand often unexpected
consequences.
Evolution myths: The bacterial flagellum is irreducibly complex
Actually, flagella vary widely from one species to another, and someof the
components can perform useful functions by themselves. Theyare anything but
irreducibly complex
It is a highly complex molecular machine. Protruding from manybacteria are
long spiral propellers attached to motors that drivetheir rotation. The only
way the flagellum could have arisen, someclaim, is by design.
Each flagellum is made of around 40 different protein components.The
proponents of an offshoot of creationism known as intelligentdesign argue
that a flagellum is useless without every single one ofthese components, so
such a structure could not have emergedgradually via mutation and selection.
It must have been createdinstead.
In reality, the term "the bacterial flagellum" is misleading. Whilemuch
remains to be discovered, we now know there are thousands ofdifferent
flagella in bacteria, which vary considerably in form andeven function.
Different strokes
The best studied flagellum, of the E. coli bacterium, containsaround 40
different kinds of proteins. Only 23 of these proteins,however, are common
to all the other bacterial flagella studied sofar. Either a "designer"
created thousands of variants on theflagellum or, contrary to creationist
claims, it is possible to makeconsiderable changes to the machinery without
mucking it up.
What's more, of these 23 proteins, it turns out that just two areunique to
flagella. The others all closely resemble proteins thatcarry out other
functions in the cell. This means that the vastmajority of the components
needed to make a flagellum might alreadyhave been present in bacteria before
this structure appeared.
It has also been shown that some of the components that make up atypical
flagellum the motor, the machinery for extruding the"propeller" and a
primitive directional control system can performother useful functions in
the cell, such as exporting proteins.
Changing zooms
It has been proposed that the flagellum originated from a proteinexport
system. Over time, this system might have been adapted toattach a bacterium
to a surface by extruding an adhesive filament.An ion-powered pump for
expelling substances from the cell mightthen have mutated to form the basis
of a rotary motor. Rotating anyasymmetrical filament would propel a cell and
give it a hugeadvantage over non-motile bacteria even before more spiral
filamentsevolved.
Finally, in some bacteria flagella became linked to an existingsystem for
directing movement in response to the environment. In E.coli, it works by
changing flagella rotation from anticlockwise toclockwise and back again,
causing a cell to tumble and then head offin a new direction.
Without a time machine it may never be possible to prove that thisis how the
flagellum evolved. However, what has been discovered sofar that flagella
vary greatly and that at least some of thecomponents and proteins of which
they are made can carry out otheruseful functions in the cells show that
they are not "irreduciblycomplex".
More generally, the fact that today's biologists cannot provide adefinitive
account of how every single structure or organism evolvedproves nothing
about design versus evolution. Biology is still inits infancy, and even when
our understanding of life and its historyis far more complete, our ability
to reconstruct what happenedbillions of years ago will still be limited.
Think of a stone archway: hundreds of years after the event, how doyou prove
how it was built? It might not be possible to prove thatthe builders used
wooden scaffolding to support the arch when it wasbuilt, but this does not
mean they levitated the stone blocks intoplace. In such cases Orgel's Second
Rule should be kept in mind:"Evolution is cleverer than you are."
Evolution myths: Yet more misconceptions
Evolution is just a theory
Yes it is, like Einstein's theory of special relativity. By
theory,scientists mean an explanation backed by evidence. What
creationistsmean is that evolution is just a hypothesis, unsupported by
evidence- which it is not. Evolution is a fact as well a theory.
Darwin recanted on his deathbed
If Einstein had recanted his theories on his deathbed, would theuniverse be
any different? Scientific hypotheses stand or fall onthe evidence, not on
the whims of their proposers. But for therecord, this myth, popular among
creationists, is not true.
There are no transitional fossils
There isn't a nice way of saying this: anyone making this claim iseither
appallingly ignorant or an outright liar. In fact, there arefar too many
fossils with intermediate features to count - trillionsif you include
microfossils. These fossils show the transitionsbetween major groups, from
fish to amphibians, for instance, as wellas from one species to another. New
discoveries are continuallymade, from the half-fish, half-amphibian
Tiktaalik to an earlygiraffe with a shorter neck than modern animals.
There are serious problems with the theory of evolution
Would you jump off a skyscraper on the basis that the clash betweengeneral
relativity and quantum theory means there are seriousproblems with our
theory of gravity? It makes no more sense toquestion the reality of
evolution because scientists are stilldebating about some of its finer
aspects than it does to questionthe existence of gravity for the same
reason. There are still plentyof details to fill in but, as surely as
dropped objects fall, lifehas and continues to evolve.
If we all evolved from apes, why are there still apes around in thisworld?
Chihuahuas, great Danes and every other type of dog were bred fromwolves,
but there are still wolves in the world. And what breedersdo deliberately
can happen naturally: when a species splits intoseparate populations that
cannot interbreed, these populations canevolve in very different ways. The
emergence of a new species doesnot necessarily mean the disappearance of the
old one, although infact the apes we evolved from are long extinct
chimpanzees andgorillas are our cousins, not our ancestors.
Evolution myths: Evolution violates the second law of thermodynamics
The second law of thermodynamics states that entropy, a measure
ofrandomness, cannot decrease in a isolated system. Our planet is nota
isolated system.
Er, that's it. There are longer ways of saying the same thing if youprefer.
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