My recent post on optimism was inspired by yet another very interesting science book that I read recently. Catastrophes: the Science of Mass Extinction by Vince Courtillot, is a fascinating romp through the evidence that catastrophic events have been an important influence in the development of life on Earth. The author not only examines the death and destruction inflicted when large space faring rocks fly out of the sky, but also discusses at some length the effects of huge plumes of magma, moving up through the Earth, and culminating in the eruption of devastating volcanic traps. All pretty terrifying (and yet compelling) stuff, and it's well worth a read.
Another skip to the end moment, with an extract from the conclusion:
In a recent article celebrating the 21st anniversary of the theory of punctuated equilibrium, the theorys primary authors, Gould and Eldredge, remark that in the natural sciences all great theories are based on the frequent repetition of the same kind of observation but do not necessarily imply the exclusivity of that observation. The gradualism of evolution is well documented for some species, as is the theory of punctuated equilibrium for others. The sticking point is to know which of the two is common enough to impose its rhythm and signal on the history of Life. Gould and Eldredge obviously make no secret of the fact that they believe observation supports a preference for their theory. I cannot resist drawing a parallel with our two catastrophist theories of mass extinctions: the slow theory of the mantle plumes and the fast theory of the asteroids. The two are not exclusive. And if we can speak of frequency where such small numbers are involved, the reader knows by now where my own sympathies lie, or more exactly which theory I think is more important to an understanding of the great changes in the direction of Life on Earth, on the grounds of seven to one.
As Gould and Eldredge say, contemporary science has massively substituted notions of indeterminacy, historical contingency, chaos and punctuation for previous convictions about gradual, progressive, predictable determinism. Mass extinctions have, in fact, often stricken down species that were extremely well adapted to their environment as long as that environment remained withinnormal and reasonable limits. The medias popularized representation of worn-out, ill-adapted, obsolete, stupid, oversized, sluggish, gluttonous, fragile-egged dinosaurs has no basis in fact. Many of these great saurians were indeed the masters of their world, and some of their species were equipped to withstand almost anything except the sky falling on their heads. Being wiped out under such conditions (whether geophysical or astrophysical) can be chalked up to bad luck. But once their disappearance was complete, evolution resumed its experiments more vigorously than ever, and the consequences, unpredictable at the outset, became inevitable.
The eruptions of the traps, which were at least in part responsible for the principal extinctions, have punctuated the history of the evolution of species (with assistance from the occasional asteroid) and thus provide an excellent illustration of the contingent model Gould describes for the astonishing Cambrian fauna of the Burgess Shale, more than 500 Ma old. In these shales from the Canadian Rockies, we find delicate imprints from the soft parts (which are very seldom preserved) of marine animals, indicating the existence in the past of anatomical plans very different from those of the organisms that have populated the Earth since then and down to our own time. Whereas at least 25 different anatomical plans rapidly developed during the Cambrian Period, only four, none of whose future success might have been predicted, actually had descendants. One survivor, Pikaia, a chordate originally thought to have been a worm, was perhaps the ancestor of all vertebrates. Nothing indicates that all those forms that died out, victims of a catastrophe of which no trace has yet been found, were any less well adapted to the Cambrian world than the few survivors.
Like a broken line, Darwinian evolution thus seems punctuated, over the very long term, by catastrophes that wiped out some experiments that had nevertheless been highly successful, and opened the way for others. This recalls the mechanism of punctuated equilibrium proper, which operates on a shorter time scale. Together with others, including Walter Alvarez, I have suggested that we should abandon the conventional expression survival of the fittest, at least over this long time scale and for these major periods in which the entire face of Life on Earth is transformed, and instead use what seems to me the more appropriate term, survival of the luckiest. Survivors are self-evidently fitter in crises, but these crises have nothing to do with the long-term conditions under which they had previously evolved. One cannot speak of adaptation to enormously rare events.
Survival of the luckiest, eh? I guess that's debatable. And in the end, it is the knowledge that chance was crucial in human evolution, that is some of the best proof that life, is indeed, pointless...Go Top