Why does evolution happen? The rules on Earth may well be universal

Dig down, and evolution by natural selection is just about spontaneous, sustained accumulation of complexity – if life elsewhere exists, it’s likely to develop in the same way

By Graham Lawton

EVOLUTION is a fact of life, at least of life as we know it. Here on Earth, organisms that just so happen to be better adapted, or “fit”, for their environment, perhaps by virtue of a fortuitous mutation, tend to survive longer and leave more offspring. The less fit leave fewer descendants and the unfit none at all. Whatever it was that made the winners fit thus accumulates in the next generation, a cruel and random Squid Game called evolution by natural selection.

As to why it happens, on one level that’s simple. According to biologist Richard Dawkins, evolution is simply a change in gene frequencies in populations. If a gene in a colony of woodlice living under a dead log becomes more or less common for some reason, evolution has happened.

But must it be like that? All life on Earth that we know of comes from the same origin and uses the same biochemical operating system based on DNA. Putative life on other planets, or “shadow life” from an independent origin on Earth, might conceivably operate under very different rules. Does life have to evolve – and if so, does that have to be by natural selection? “That’s a very interesting and large question,” says Dawkins.

Arik Kershenbaum at the University of Cambridge, author of The Zoologist’s Guide to the Galaxy: What animals on Earth reveal about aliens – and ourselves, thinks the alternatives are limited. One might be to postulate an intelligent designer, as perhaps we ourselves might someday design self-replicating organisms. But …