Evolution: Predictable?

Evolution is change in the characteristics of species and heritable characteristics of biological populations over generations. But can we call it predictable? This has been debatable over years. Researchers at Kenyon College, Michigan State University and Washington University in St. Louis closely examine evidence from a number of empirical studies of evolutionary repeatability and contingency to fully interrogate ideas about contingency's role in evolution.

Stephen Jay Gould, the late paleontologist, raised the concern on evolution's predictability in his 1989 book Wonderful Life. He thought "Replay the tape a million times and I doubt that anything like Homo sapiens would ever evolve again," noting that being able to "replay the tape" and give history a do-over would be impossible. Since then, many evolutionary biologists challenged themselves and experimented the same on smaller scales. As a result, there were many conclusions about the interplay between randomness of mutations, chance historical events, and directionality imparted by natural selection. All of us, in our lives, have definitely thought of starting everything from fresh, haven’t we? Many biologists have also shown interest in the unpredictability of evolution. Since Gould introduced the metaphor of replaying life's tape, many studies have tried to characterize the repeatability of evolution. Jonathan Losos, the William H. Danforth Distinguished University Professor at Washington University in St. Louis, said "There are multiple, different literatures on Gould's idea, and these literatures are not talking to each other". "There are microbial evolution studies. There are all the studies of convergent evolution, or lack of convergent evolution and there's also a philosophical literature on what Gould meant when he said, 'replay the tape.' That is, more generally, when you talk about the role of contingency -- which is the term Gould used -- what does that actually mean?" Many different laboratory experiments have been conducted where identical populations of an organism are separately evolved under identical conditions, and analytic replay experiments, in which specimens are frozen from a parallel replay experiment and then re-evolved from different points in time. This review included study of the long-term evolution experiment with Escherichia coli (LTEE), started by Lenski in 1988. The LTEE has followed 12 populations of E. coli, founded from a single clone, for more than 70,000 generations. The samples of every 500 generations have been compared for the evolving bacteria with their ancestors. Few experiments were done that exist till date which concluded a high degree of repeatability in evolutionary responses to different historical conditions. But now the question is all about that convergence occur sometimes but not at other time. Their review was supported in part by a grant from the National Science Foundation, the BEACON Center for the Study of Evolution in Action, Michigan State University and Harvard University.

By: Anuja Arora

Content: https://www.sciencedaily.com/releases/2018/11/181108142323.htm