Cambridge zoologist Arik Kershenbaum, author of Zoologist’s Guide to the Galaxy (2021), thinks that convergent evolution here on Earth can offer us guides to what must happen on other planets that can support life. “Convergent evolution” means that radically different life forms arrive at the same solutions. He told science writer Dan Falk in an interview:
Sometimes this “convergence” of traits is for something obviously useful, like wings. But sometimes convergence produces bizarrely similar creatures that share so many characteristics, it can be hard to believe they’re not closely related. The recently extinct thylacine [a large predatory marsupial native to Tasmania and mainland Australia], for example, could easily be mistaken for a peculiar breed of dog, but it’s much more closely related to a kangaroo! And yet living a life similar to that of modern coyotes or jackals meant that it evolved many similar characteristics convergently.
Dan Falk, “Why Extraterrestrial Life May Not Seem Entirely Alien” at Quanta (March 18, 2021)
Kershenbaum believes that “laws of evolution” govern what can possibly happen, due to the physics of the universe. He told Falk:
On Earth, flight evolved four different times in four different groups: in birds and bats and pterosaurs and insects. The fact that they all use wings isn’t because they evolved on Earth; it’s because it was advantageous to fly, and wings are just about the only way to fly. And so we can expect these constraints to be operating everywhere in the universe.
Dan Falk, “Why Extraterrestrial Life May Not Seem Entirely Alien” at Quanta (March 18, 2021)
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