Stephen Jay Gould gets a bit of a bashing in Dennett's 'Darwin's Dangerous Ideas', and not knowing much about him, I decided to see what all the fuss was about. Gould died in 2002, shortly after publishing his book, 'The Structure of Evolutionary Theory' and I found this interesting review at Popmatters, which covers a lot of the controversial issues:
Consider nipples on men. Adaptation can't be a "universal result" of natural selection because nipples on men are nonadaptive, unless you're willing to believe that cavemen nursed their young. Gould called these nonadaptive features "spandrels" and said that such useless side effects are so common in nature that you can't call evolution progressive. Because the term "evolution" is synonymous with "progress," Gould's theory rendered the term a misnomer, and elicited howls from the scientific community. Gould believed that natural selection causes some organisms to devolve or stay the same. In one of his greatest popular works, Full House, Gould uses bacteria as an example:
"Life therefore began with a bacterial mode. Life still maintains a bacterial mode in the same position. So it was in the beginning, is now, and ever shall be-at least until the sun explodes and dooms the planet. How, then, using the proper criterion of variation in life's full house, can we possibly argue that progress provides a central defining thrust to evolution if complexity's mode has never changed?"
Just look at the bug that's shaped exactly like a leaf to disguise itself from predators to see how evolution can be progressive, but Gould's point is that no progressive trend exists in nature. And for many scientists and non-scientists alike, that just sucks. The idea of a Godless universe sucks, but the notion of nature working in our best interest softens the blow-you can wonder whether some kind of deity is behind the benign force. By dispelling that notion too, Gould really let the hammer down, and he made plenty of enemies in doing so.
Creationists love Sir Fred Hoyle’s vivid metaphor for his own misunderstanding of natural selection. It is as if a hurricane, blowing though a junkyard, had the good fortune to assemble a Boeing 747. Hoyle’s point is about statistical improbability. Our answer, yours and mine and Stephen Gould’s, is that natural selection is cumulative. There is a ratchet, such that small gains are saved. The hurricane doesn’t spontaneously assemble the airliner in one go. Small improvements are added bit by bit. To change the metaphor, however daunting the sheer cliffs that the adaptive mountain first presents, graded ramps can be found the other side and the peak eventually scaled. Adaptive evolution must be gradual and cumulative, not because the evidence supports it (though it does) but because nothing except gradual accumulation could, in principle, do the job of solving the 747 riddle. Even divine creation wouldn’t help. Quite the contrary since any entity complicated and intelligent enough to perform the creative rôle would itself be the ultimate 747. And for exactly the same reason the evolution of complex, many-parted adaptations must be progressive. Later descendants will have accumulated a larger number of components towards the adaptive combination than earlier ancestors.
The evolution of the vertebrate eye must have been progressive. Ancient ancestors had a very simple eye, containing only a few features good for seeing. We don’t need evidence for this (although it is nice that it is there). It has to be true because the alternative – an initially complex eye, well-endowed with features good for seeing – pitches us right back to Hoyle country and the sheer cliff of improbability. There must be a ramp of step-by-step progress towards the modern, multifeatured descendant of that optical prototype. Of course, in this case, modern analogs of every step up the ramp can be found, working serviceably in dozens of eyes dotted independently around the animal kingdom. But even without these examples, we could be confident that there must have been a gradual, progressive increase in the number of features which an engineer would recognize as contributing towards optical quality. Without stirring from our armchair, we can see that it must be so.
Now it is important to stress that, on this adaptationist view (unlike the ‘evolution of evolvability’ view to be discussed shortly), progressive evolution is to be expected only on the short to medium term. Coevolutionary arms races may last for millions of years but probably not hundreds of millions. Over the very long timescale, asteroids and other catastrophes bring evolution to a dead stop, major taxa and entire radiations go extinct. Ecological vacuums are created, to be filled by new adaptive radiations driven by new ranges of arms races. The several arms races between carnivorous dinosaurs and their prey were later mirrored by a succession of analogous arms races between carnivorous mammals and their prey. Each of these successive and separate arms races powered sequences of evolution which were progressive in my sense. But there was no global progress over the hundreds of millions of years, only a sawtooth succession of small progresses terminated by extinctions. Nonetheless, the ramp phase of each sawtooth was properly and significantly progressive.
And you see, that's life. Chance has always been a part of evolution. We may not know what the universe is exactly, but we know that life is ultimately pointless - and that natural selection played an important part in building us (though we were not inevitable and the universe was not made for our species).Go Top