[tt] NYT: Seeing the Risks of Humanity's Hand in Species Evolution

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Seeing the Risks of Humanity's Hand in Species Evolution
http://www.nytimes.com/2009/02/10/science/10humans.html

By CORNELIA DEAN

According to the sages who issued the Biblical edicts of
Deuteronomy, if you come upon a bird's nest, you may take eggs and
nestlings, but you must leave the mother bird behind. "Let the dam
go," the King James version says.

Some consider this advice as odd as many of Deuteronomy's other
injunctions, like its ban on clothing made of blends of linen and
wool. It runs counter to the fishing tradition of throwing the small
fry back so they can grow up, aiming for the largest males in trophy
hunting.

But now some biologists are starting to think Deuteronomy has it
right. They see this approach as a remedy for a growing
environmental problem -- the way human predation is causing target
species to evolve to reproduce at younger ages and smaller sizes, to
their short-term benefit but to the long-term harm of the species.

"Humans are frighteningly efficient predators," said J. Stanley
Cobb, a lobster expert who retired recently from the University of
Rhode Island. "They impose mortality in specific ways, at particular
stages of the life cycle. If we believe that natural selection has
shaped the life history characteristics of a species, then we have
to believe that a different mortality regime will affect life
history."

Because humans discovered fire, the benefits of hunting in teams and
the bounties of agriculture, people have been changing the natural
landscape, causing plants and animals to evolve in response.

Starting perhaps 12,000 years ago, when people in what is now the
Middle East began turning wolves into dogs, humans have domesticated
animal species as varied as cows to cats. They initiated or
encouraged changes that turned weedy grasses into crop plants like
rice and corn. Stone age hunters may even have helped drive some
ancient creatures, like wooly mammoths, to extinction.

In a report in Friday's issue of the journal Science, researchers
led by Jeff Feder, a biologist at Notre Dame, say the introduction
of apples to North America in the 17th century eventually led some
fruit flies that had specialized on hawthorn fruit to branch out to
apples instead. By the mid-1800s, the scientists say, the two groups
of flies had become genetically different. And that, in turn,
encouraged modifications of parasitic wasps that feed on the flies.

"It's a nice demonstration of how the initial speciation of one
organism opens up an opportunity for another species," Dr. Feder
said in a statement.

Human behavior has affected human evolution as well. Cattle-herding
peoples developed an ability to digest milk as adults through
mutations that provided a definite survival advantage when times
were hard.

But those were low-tech days. Since the beginning of the Industrial
Revolution, humanity's collective ability to change the world has
been powered by fossil fuels and multiplied by machines. Often, the
result has been evolutionary change at a fast pace and on a broad
scale.

Researchers have long known that bacteria evolve to evade
antibiotics, and that parasites, like those that cause malaria,
adapt to drugs used against the disease. More recently, researchers
have reported that cod, overfished for decades off New England and
the Canadian Maritime Provinces, have begun reproducing at younger
ages and smaller sizes. Other scientists have reported similar
changes in species as diverse as bighorn sheep, caribou and ginseng
plants.

The shift improves the chances of reproducing before being killed.
But at least as far as the fish are concerned, the change is harmful
in the long run, according to Paul Paquet, an environmental
scientist at the University of Calgary. The spawn of younger fish do
not seem to be as robust as the spawn of older fish.

"It's forced evolution," he said. "It is not working to their
advantage."

Fishery officials in Maine, eager to preserve the state's lucrative
lobster catch from similar effects, now say fishers must release any
lobster not just if it is small, but also if its shell is larger
than 5 inches.

"This law exists to protect breeders," the Atwood Lobster Company,
one of the state's major distributors, tells would-be customers on
its Web site. "Larger lobsters are capable of reproducing greater
and healthier numbers of offspring, and Maine lobster harvesters
feel very strongly about protecting this brood stock."

Like other lobster-producing states, Maine also requires fishers who
trap egg-bearing females to mark them with a small "V-notch" and
throw them back. Anyone who in turn catches one of these notched
lobster must also throw it back.

But the effects of this kind of regulation can be hard to predict.
In Rhode Island, Dr. Cobb said, a notching program began about a
decade ago, after an oil spill killed many lobsters. Initially, he
said, it was so successful "the sex ratio went all out of whack," to
the point that researchers estimated that 75 percent of the state's
lobsters were female, a situation that can work against reproductive
success.

"The concern is for sperm limitation," he said, adding that a
similar problem had been seen with blue crabs. The end result was
more lobster eggs but not more baby lobsters in state waters.

In many areas of the West, conservationists hope to maintain genetic
diversity in deer, bears and other species by building tunnels and
overpasses to allow them access to their full range, even if it is
now divided by highways. But often the animals have already adapted
to their newly humanized habitats. Deer thrive on suburban shrubs.
Black bears in Nevada dine so well at garbage cans and dumpsters
that they have more and healthier cubs than their country cousins.

In another report in Science last week, researchers from Stanford
and elsewhere reported that wolves and coyotes with dark coats may
have originally gained a gene for darkness by mating with their
humanized kin, dogs. Conservation purists often cringe at the mixing
of wild and domesticated animals, but as the wolves and coyotes
confront shrinking wild habitat, the researchers said, the
introduction of genes from domesticated animals may turn out to help
them.

As climate warms, plants in the Rocky Mountains are moving to higher
elevations, where it is cooler. In some areas of New England,
researchers report that trees, shrubs and flowers are in bloom a
week or two earlier than they were even a century ago. And the cast
of characters seems to be changing in the tide pools of Monterey
Bay, where plants and animals adapted to warmer water seem to be
moving in.

Sometimes, researchers report, invasive species can add to the
biological richness of a given habitat. But that kind of change can
be a problem for conservation organizations that buy land seeking to
preserve a particular ecosystem, only to find that it is shifting
out from under them.

In addition, when plants, birds and insects have evolved en suite to
sync their hatching, blooming or migrating patterns, individual
changes can leave nestlings hatching too late to dine on their
favored swarming insects, or flowers blooming ahead of the arrival
of the birds they need to pollinate them.

People have also brought technology to bear on themselves. But so
far at least, "the accomplishments have been minimal," said
Francisco Alaya, an evolutionary biologist at the University of
California, Irvine. He cited treatments for diseases like Type I
diabetes that allow people who might otherwise have died in
childhood to grow up and pass their health defects on to their
descendants.

He predicts it will be a long time before geneticists are able to
manipulate genes to improve the human species, especially because
the genetic influence on desirable traits, like high intelligence or
ethical behavior, is so complex and so meshed with environmental
factors. Even the traits themselves, he said, are hard to define.

Anyway, he said, "if we start to change genes, how many people are
we going to manipulate? A hundred? A thousand? A million? Still it
will be a very little fraction."

Dr. Ayala said he found it far more interesting to contemplate the
way humans have improved their scope as a species by cultural
evolution.

"We are still biologically adapted to tropical climates," he said.
"Yet we have populated the continents of the earth without changing
our physiology. We just use clothing and housing and heating and air
conditioning. We travel the oceans without scale, and we fly without
having evolved wings."