Here is a simple truth that you won’t hear from all the high priests and popularisers of science (in this case, biology):
“If you dissect the past, you can see that luck is a big part of everything in the grand scheme of evolution,” says lead author Stephen Brusatte, a researcher at the American Museum of Natural History.
The researchers whose work is being commented upon above, examined the historical record of dinosaurs and crurotarsans:
[E]arly dinosaurs were contemporaries of crurotarsans, croc ancestors, during the late Triassic period about 230 to 200 million years ago. This reptilian group ranged from quick predators to two-legged vegetarians to leisurely grazers. Then, as the Triassic turned into the Jurassic, the creatures roaming the planet changed drastically. Most crurotarsans disappeared from the fossil record. But many dinosaurs survivedâ€”and flourished, diversifying into meat-eating giants, armored warriors and winged aviators.
But, they caution:
If dinosaurs were more fit for the environment, they should have had a higher rate of evolution and more diverse body types. Instead the researchers found that the two groups evolved at similar rates and that the crurotarsans had a wider range of body types, suggesting that they had actually adapted to more lifestyles and ecological niches.
The authors argue that because dinosaurs and crurotarsans were living parallel lives together for so long, it is unlikely the dinosaurs necessarily ruled. If you could travel back to the Triassic, Brusatte says, you would have guessed that the crocodilians would have won out. “There’s no way you could argue that dinosaurs were superior to them,” he says. Instead, he thinks an extinction event at the beginning of the Jurassic some 205 million years agoâ€”like runaway global warming or an asteroid crashâ€”may have just been bad luck for the crurotarsans.
The orthodoxy has objections:
“I think that the conclusions of the authors aren’t warranted,” says Kevin Padian, a dinosaur paleontologist at the University of California, Berkeley. “Good luck isn’t an evolutionary forceâ€¦. Extinctions aren’t random.”
I am no evolutionary biologist or paleontologist, but this sort of response seems to miss the point, logically speaking. Properly understood, there is no implication that there is true randomness in evolution — or rather survival (after all, all events have causes). Rather, it seems to me, the parsimonious claim is that species flourish or perish not entirely due to their own adaptations in the constant presence of environmental pressures (and while we are at it, I thought multi-level selection was taboo and we are only to talk of individuals, not species?), but also often due to large environmental events that alter their fate. One could of course present these events as selective pressure and the pre-existing advantages of the organism as “adaptations” but I think such a tautology would rob the theory of much of its value.Read the full post and comments »