Thoughts about Earth as it is
Posted by 1minionsopinion on November 25, 2009
Olivia Judson has an interesting take on an Evolve-By Date that’s worth commenting on. I offer my own thoughts between paragraphs.
I’ve written before about what an important book it was and why it mattered so much, so I won’t do that again now. Instead, I want to mark the occasion by looking at the limits of evolutionary potential.
To see what I mean by this, consider the following paradox. Whenever we do evolution experiments in the laboratory or on the farm, we can cause pronounced and rapid change in the traits we are interested in — we can evolve bigger horses, smaller dogs, cows that make more milk, viruses that thrive at higher temperatures and so on.
That’s not natural evolution; those are examples of genetic engineering. That’s human beings forcing their way into a species’ inner workings to manipulate natural ability until it results in what might be a very unnatural ability. Evolution is the natural process by which a species adapts to its environment over time. Specialized breeding and gene tweaking and drugs work faster than evolution does. Every breed of dog or cow or horse or sheep or chicken out there has been humanly guided into those breeds over hundreds of years. Just look into the history of husbandry.
Nature maybe could have changed these animals, given thousands of years, or it might not have. If there was no need for the animal to change that much, it wouldn’t have changed. Humans wanted them to change, so we changed them.
In the laboratory, in other words, evolution has huge potential. But if it has that much potential — how come organisms keep going extinct in nature? In other words, why does evolution keep failing?
Evolution isn’t failing. Humans are. Humans killed off the dodo. That’s not the fault of the dodo. There was no way the species could have evolved in such a short time into a critter wise enough to hide or run from human beings. Humans knock forests down with little regard to what kind of species might rely on it. Humans want the pelts, teeth, bones, eyeballs, feathers, blubber, off all kinds of animals often without caring about poaching laws. There’s big money to be had if something’s hard to get. Humans got it into their heads that rhinoceros horns were an aphrodisiac. The rhinos are incapable of debating that. Tigers can’t stop people from taking their penises for the same reason. And plants are also at risk of extinction.
The question matters as never before. 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.
Look at the trouble Florida residents have with alligators. Land developers encroached on the swamps they’ve lived in for thousands of years and now there’s a swimming pool where a nesting site used to be. You can’t explain to an alligator that it’s time he moves on. If he even understood the concept, what land is left for him anyway? Cities have wild cat problems for the same reason. They’ve spread into the areas cougars used to have to themselves so they’re adapting in a way humans don’t like very much at all. Raccoons do the same. I’ve heard they’re quite nasty and destructive once they squat in an attic or under a porch and are hellish to get rid of. Animals are incapable of evolving into anything else that would save their lives. All they can do is attempt to change the way they behave, but since a lot of that relies on evolved instinct, fat chance. Evolution isn’t a Kevlar vest they can strap on to stop bullets. Everything can adapt to a point, but humans are unstoppable unless we stop ourselves.
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.
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.
Sobering thought indeed.