IT is once more our delight, dear reader, to post about a column by the splendidly-evolved Olivia Judson — an evolutionary biologist and a research fellow in biology at Imperial College London. This article, part of Dr. Judson’s series in the New York Times, is titled: An Evolve-By Date. Here are some excerpts, with bold added by us:
We humans are busily changing the environment for most of the beings on the planet, and often, we are doing so very fast. To know what effect this will have, we badly need to know how readily different creatures can evolve to deal with changes to their environment. For if we’re not careful, many groups will soon be faced with an evolve-by date: if they don’t evolve rapidly enough to survive in this changing world, they will vanish.
That’s the way of the world. Most species have become extinct. Let’s read on:
The basis of evolutionary potential is clear enough in principle. Whether a population can evolve to cope with new circumstances depends on how much underlying genetic variation there is: do any individuals in the population have the genes to cope, even barely, with the new environment, or not? If not, everybody dies, and it’s game over. If yes, evolution may come to the rescue, improving, as time goes by, the ability of individuals to cope in the new environment.
Quite so. That’s how the game is played. We continue:
What determines the extent of the underlying genetic variation? Factors such as how big the population is (bigger populations usually contain more genetic variation) and how often mutations occur.
Right. The more, the merrier. Olivia then says:
Suppose you put bacteria into test tubes where their usual sugar source is in short supply, but an alternative one — which they can’t consume at all — is abundant. (If you put them with just this alternative source, they would all die of starvation at once.) Then, you can watch how long it takes for the bacteria to evolve so they can digest the alternative. The answer, in one famous case, was more than 31,000 generations! Which just goes to show: just because a particular trait would be useful does not mean that it will soon evolve.
A pessimistic result, but it was achieved with a limited population sample. Here’s Olivia’s concluding paragraph:
To me, all this is a bit sobering. If most organisms have to wait 31,000 generations to evolve a useful new trait — they will probably go extinct first. Worse, many natural populations are shrinking fast, further reducing their evolutionary potential. In short, we can expect that — if the environment continues to change as rapidly as it is at the moment — many creatures will fail to meet their evolve-by dates.
That’s the way it is. Out with the dinosaurs, in with the mammals. And speaking of mammals, isn’t Olivia the greatest?
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