Extinction: "Weird internal motor" of evolution? Effect of galactic history?
In an interesting article in Current Biology (September 20), paleontologist Simon Conway Morris argues that human-life creatures would have arisen even if the dinos had not gone extinct:
The bolide misses and the dinosaurs go home for tea... You know the mantra: no K/T impact, no dinosaur extinctions, so no mammalian evolutionary radiations, so neither primates nor in due course apes and so ultimately no us. True, but trivial. Imagine a counterfactual Earth, with no K/T impact. Twenty million years later the planet still sails into major glaciations. Dinosaurs are doing fine, thank you, but look what's happening in the cooler temperate and polar regions. Warm-blooded critters are taking the initiative. Both birds and mammals are intelligent, social and have a tendency to make tools. This means that sooner or later a sentient species with technology will emerge: the demise of the heavy brigade is inevitable. Mass extinctions may accelerate (maybe postpone), but they never cancel.
This is, of course, the opposite of Stephen Jay Gould's position, espousing radical randomness of outcomes for evolution, as exprssed in Wonderful Life.
Morris also weighs in on whether extinctions are periodic:
Discussion of whether mass extinctions are cyclic ebbs and flows. At the moment most pundits say 'no', but the evidence remains intriguing. If correct, either biological diversity has some weird internal motor, or more likely the fossil record is telling us something about galactic history. Recall that presently the Solar System is embedded in what astronomers call the Local Bubble, but in the past-and future- when the Solar System encounters interstellar clouds, the heliosphere will shrink, with consequences such as a change in cosmic ray flux. Now that is beginning to sound interesting.
Yes, it begins to sound interesting. And in even speculating about a "weird internal motor", Conway Morris is beginning to sound like the ID advocates he has no use for. I suspect, along with the late David Raup, that critical to understanding evolution is understanding extinction.
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Now back to the blogging conference.
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