[tt] NYT: A Toast to Evolvability and Its Promise of Surprise

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A Toast to Evolvability and Its Promise of Surprise
New York Times, 7.3.6
http://www.nytimes.com/2007/03/06/science/06angi.html

Basics
By NATALIE ANGIER

Late last month, the day after my birthday, I was feeling punch
drunk on my favorite glogg of sullenness, self-pity and panic. My
life was passing by at relativistic speed, not one of my rotten
siblings had called to wish me a happy birthday, my husband hadnt
bothered to arrange so much as a waiter-serenaded slice of cake at
the restaurant the night before, and did he really think that his
gift to me of an amazing squirrel-proof bird feeder would excite
anybody but the squirrels?

My post-birthday gloom was so rich, so satisfyingly glutinous, that
I forgot to be suspicious, and when we headed over to a neighbors
house later that evening, I opened the door like a cartoon buffoon
onto a huge throng of friends and relations, gathered from across
the nation and athwart my entire curriculum vitae, bellowing out in
fractured synchrony that magic word Surprise! I gasped. I squealed.
I felt like Id died and gone to a TV game show. Id gotten the
surprise party of my admittedly oft-expressed fantasies, and I was
thrilled, moved and profoundly grateful. Yet as I stumbled in a
stupor from one friend whod spent hundreds of dollars on airfare
just to be there to the next, I couldnt help wondering why Id
wanted such a shock to my system in the first place.

Im not much of a thrill seeker or adventurer. I like libraries,
museums and speed bumps. I am, nevertheless, a multicellular
organism of reasonably complex structure, and we complex bioforms
cant help but appreciate novelty. We are the fruits of it. If not
for evolutionary novelty that is, the periodic and often radical
overhauling of an existing cell type, body plan, limb shape or
brain design into something new and useful, or at least
entertaining we might still be so many daubs of blue-green algae
decorating an Australian rock. And while I mean no offense to algae
and recognize that my ancestors looked very much like them, an
algal colony has yet to throw me a surprise party or make a
passable stab at saying Gday.

A tip of the paper-cone hat, then, to biological novelty. Under its
tutelage, early groups of cells made the leap from the sleepy
expulsion of oxygen as waste to the aerobic consumption of oxygen
to grow at a hastier pace; and groups of single cells learned to
pool their talents into multicellular collectives of specialized
body compartments that could then go out and hunt other
multicellular collectives; and fishy fins became amphibious feet
and crept onto the beach, and some land-weary feet changed their
mind and flippered back to the sea, while still other limb bones
lengthened and found skin flaps for flying, and, hey, this airborne
business is pretty handy, lets rearticulate the forelimbs of three
separate lineages and take wing as a pterodactyl, a bird, a bat.

As scientists see it, these and others of natures fancy feats
forward are clearly the result of large-scale evolutionary forces,
but the precise mechanisms behind any given innovation remain
piquantly opaque. For some researchers, the conventional gradualist
narrative, in which organisms evolve over time through the steady
accretion of many mincing genetic mutations, feels unsatisfying
when it comes to understanding true biological novelty.

The standard Darwinian view always sounds like a better theory for
making improvements than for making inventions, said Dr. Marc W.
Kirschner, a professor of systems biology at Harvard Medical
School. If incremental, additive genetic changes were responsible
for all the boggling biodiversity we see around us, he said, how
can it be that humans have hardly more genes than a microscopic
nematode, and that many of those genes are nearly identical in
roundworms and humans besides?

In their recently published book, The Plausibility of Life, Dr.
Kirschner and Dr. John C. Gerhart of the University of California,
Berkeley, offer a fresh look at the origins of novelty. They argue
that many of the basic components and systems of the body possess
the quality of what they call evolvability that is, the components
can be altered without wreaking havoc on the parts and systems that
connect to them, and can even produce a reasonably functional organ
or body part in their modified configuration. For example, if a
genetic mutation ends up lengthening a limb bone, said Dr.
Kirschner, the other parts that attach to and interact with that
bone neednt also be genetically altered in order to yield a
perfectly serviceable limb. The nerves, muscles, blood vessels,
ligaments and skin are all inherently plastic and adaptable enough
to stretch and accommodate the longer bone during embryogenesis and
thus, as a team, develop into a notably, even globally, transformed
limb with just a single mutation at its base. And if, with that
lengthened leg, the lucky recipient gets a jump on its competitors,
well, gday to you, baby kangaroo.

Dr. Kirschner also observes that cells and bodies are extremely
modular, and parts can be moved around with ease. A relatively
simple molecular switch that in one setting allows a cell to
respond to sugar can, in a different context, help guide the
maturation of a nerve cell. In each case, the activation of the
switch initiates a tumbling cascade of complex events with a very
distinctive outcome, yet the switch itself is just your basic
on-off protein device. By all appearances, evolution has flipped
and shuffled and retrofitted and duct-taped together a
comparatively small set of starter parts to build a dazzling
variety of botanic and bestial bodies.

The combined modularity and bounciness of body parts suggest that
life is spring-loaded for change, for outrageous commixtures, the
wildest fusion cuisine. And who knows whether our organismic
suppleness, our deep evolvability, isnt related to our mental
thirst for the new, and our hope that behind the door lies the best
surprise yet?