Chance: The importance of randomness in evolution

 作者:侴耄驸     |      日期:2019-03-15 07:06:02
By Bob Holmes How much of evolution relies on randomness? (Image: Collage: Eugenia Loli; Illustration: Katelyn Daubek) TAKE 100 newly formed planets of one Earth mass. Place each in the habitable zone of a G-type main sequence star. Set your timer for 4 billion years. What do you get? A hundred planets teeming with life forms quite similar to those on Earth, perhaps even dominated by naked apes? Or would evolution produce very different outcomes every time, if life even got started at all? Some biologists argue that evolution is a deterministic process, that similar environments will tend to produce similar outcomes. Others, the most famous of whom was Stephen Jay Gould, think its course follows unpredictable twists and turns, and that the same starting point can lead to very different results. The answer does matter. If the Gould camp is right, the study of evolution is like the study of history: something we can understand only in retrospect. If, however, the vagaries of chance play just a minor role, then biologists can predict the course of evolution to a large extent – and predicting evolution is crucial to stopping tumours becoming drug-resistant, or bacteria shrugging off an antibiotic, or bedbugs becoming immune to pesticides, or viruses killing people who have been vaccinated against them and so on. So which is it? We might not have 100 Earths and a time machine, but we can look at how evolution has turned out on, say, neighbouring islands,