Thursday, July 31, 2008
The Panda's Thumb
Our book today is The Panda's Thumb, the 1980 collection of natural history essays by Stephen Jay Gould, who published them all originally in his "This View of Life" column for Natural History magazine, back when that publication was (largely due to his presence month after month) still worth reading.
Gould was an evolutionary biologist, an entomologist, an anthropological theorist, and, more than any of those things (and the half-dozen or so other interdisciplinary hats he wore from time to time), a natural-born teacher, able to summarize and jazzercise virtually any subject, no matter how abstruse, into eight or ten jaunty, inviting pages anybody on Earth would enjoy reading. This is not a trait often found in scientists, and it is not to be scorned (the ones who do scorn it, both inside and outside the scientific world, are invariably the ones who can't do it, or who are too lily-livered to try). Given a small lead-time and no more reference-works than could be found in his overstuffed personal library, Gould could write an essay on, say, neotony, that you could not only hand to your fundamentalist grandmother but that would leave her wanting more. And he did it all amiably, without ever striking a strident note.
This last is all the more remarkable when viewed alongside his peers, some of whom could be very strident indeed. The mind naturally turns to Richard Dawkins, who shared an intellectually heated - and temporarily famous - exchange of letters with Gould in the pages of The New York Review of Books years ago - letters in which Gould comes off the better. Dawkins' 'selfish gene' idea of gene-dominated evolutionary drives never met with much enthusiasm from Gould, as he writes at one point in The Panda's Thumb:
Still, I find a fatal flaw in Dakwins's attack from below. No matter how much power Dawkins wishes to assign to genes, there is one thing that he cannot give them - direct visibility to natural selection. Selection simply cannot see genes and pick among them directly. It must use bodies as an intermediary. A gene is a bit of DNA hidden within a cell. Selection views bodies. It favors some bodies because they are stronger, better insulated, earlier in their sexual maturation, fiercer in combat, or more beautiful to behold.
If, in favoring a stronger body, selection acted directly upon a gene for strength, then Dawkins might be vindicated. If bodies were unambiguous maps of their genes, then battling bits of DNA would display their color externally and selection might act upon them directly. But bodies are no such thing.
Gould will be known in the science-history books mainly as the co-creator (along with Niles Eldredge)(who, with a colleague like Gould, ought to legally change his first name to "along with") of the idea of punctuated equilibrium: the concept that the process of evolution by natural selection is far from the stately, Lyellian progression tradition had made it out to be:
A new species can arise when a small segment of the ancestral population is isolated at the periphery of the ancestral range. Large, stable central populations exert a strong homogenizing influence. New and favorable mutations are diluted by the sheer bulk of the population through which they must spread. They must build slowly in frequency, but changing environments usually cancel their selective value long before they reach fixation. Thus, phyletic transformation in large populations should be very rare - as the fossil record proclaims.
Gradualism, the belief that all change must be smooth, slow, and steady, was never read from the rocks. It represented a common cultural bias, in part a response of nineteenth-century liberalism to a world in revolution. But it continues to color our supposedly objective reading of life's history.
But the history of life, as I read it, is a series of stable states, punctuated at rare intervals by major events that occur with great rapidity and help to establish the next stable era. Prokaryotes ruled the earth for three billion years until the Cambrian explosion, when most major designs of multicellular life appeared within ten million years. Some 375 million years later, about half the families of invertebrates became extinct within a few million years. The earth's history may be modelled as a series of occasional pulses, driving recalcitrant systems from one stable state to the next.
Gould's essays (The Panda's Thumb contains such classics as "Piltdown Revisited," "Were Dinosaurs dumb?" and the glowingly inimitable "A Biological Homage to Mickey Mouse") dance happily from one subject to the next, as Gould's own interests did (baseball and Gilbert & Sullivan get equal - and equally loving - attention). And always he returns to the big picture, the broader canvas on which the forces of evolution work and one which he tried to think (and succeeded more often than most mortals ever come close):
The best illustration of dinosaurian capability may well be the fact most often cited against them - their demise. Extinction, for most people, carries many of the connotations attributed to sex not so long ago - a rather disreputable business, frequent in occurence, but not to anyone's credit, and certainly not to be discussed in proper circles. But, like sex, extinction is an ineluctable part of life. It is the ultimate fate of all species, not the lot of unfortunate and ill-designed creatures. It is no sign of failure.
The remarkable thing about dinosaurs is not that they became extinct but that they dominated the earth for so long. Dinosaurs held sway for 100 million years while mammals, all the while, lived as small animals in the interstices of their world. After 70 millions years on top, we mammals have an excellent track record and good prospects for the future, but we have yet to display the staying power of dinosaurs.
It's not given to science-writers like Gould to have much staying power at all, and slowly, one by one, his many delightful titles will proceed out of print. But the books themselves will always lurk in the interstices, available for your curious mind. The man himself died in 2002, far too early, but echo of his many enthusiasms can be found in books like The Panda's Thumb, from Marathon to Waterloo in order categorical.