Friday, August 10, 2018

Improbable Destinies: Fate, Chance, and the Future of Evolution I

I'm moving along in this medium-length book by the evolutionary biologist Jonathan Losos. Losos surveys current research trends in the field and highlights the change in emphasis that has occurred over the last few years. In 1989, Stephen Jay Gould, the evolutionary biologist, published Wonderful Life, perhaps his best-known book, which describes the research of Simon Conway Morris, the British evolutionary biologist, on the fossils in the Burgess Shale of Canada, dating from the Cambrian period, about 500 million years ago. Gould thought that the creatures found in the Burgess Shale were bizarre one-offs that had no current descendants and provided an example of the boundless variety of life forms created by evolutionary processes. Since then, it has been determined that some of those fossils do have living descendants, and Conway Morris has shifted his focus to convergence, in which evolutionary processes create similar organisms that each adapt to specific environments and come to resemble each other in multiple ways. A general example of convergence is the similarity in appearance of three completely different large ocean predators, the shark, the ichthyosaur and the dolphin. A specific example of convergence is the beaked sea snake, which earlier was thought to be a single species; recent analysis has shown that it is two separate species, one of which evolved in the seas of Australia and the other in the seas of Asia. The two species are almost identical in appearance and behavior, but are genetically unrelated.

Convergence is not a new idea and can be traced to Charles Darwin. However, until recently it was difficult to study, and the prevailing view on evolution was that its process was governed by randomness, with no such thing as an optimal organism, and each species haphazardly evolving toward survival in some niche within an ever-changing environment. Convergence can now be better understood by observing the real-time evolution of a species on different islands with similar ecosystems, and this is what Losos has been researching with lizards in the Caribbean. Additionally, DNA analysis now makes it easier to determine relatedness and keep track of speciation.

Some of my views on evolution are probably a little dated, because until now I was unfamiliar with this research. However, I am a little leery of the direction in which Conway Morris is taking the field. As far as I've read, he seems to be pursuing something that resembles teleology, with the evolutionary production of optimal organisms that eventually display perfect adaptation to an environment, as if demonstrating the will of God. Losos discusses a hypothetical scenario in which, if the asteroid that struck the earth about 65 million years ago had missed, the dinosaurs may not have become extinct, mammals may never have become a dominant class, and the dinosaurs may have evolved into a human-like form. The reasoning is that evolution favors higher intelligence, which requires a large brain in relation to body size, and that standing upright with a large head balanced on top of the spine is the most efficient configuration for this to work. Most reptiles have long, horizontal bodies, with small heads on one end and tails on the other for balance; with a large head, this configuration would be physically untenable. Thus, if dinosaurs had remained dominant, we might still be small, furry mammals scurrying around in the woods, and the descendants of dinosaurs might look similar to us.

I don't think Losos is going to end up endorsing any extreme views, and I'll write about that when I finish the book. Losos is a clear writer, but he seems to be consciously writing for a young audience and goes out of his way to present himself as a grown-up high school science nerd: this deviates from my ideal nonfiction writing style, but his content is quite worthwhile nonetheless.

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