High Speed Evolution

Taco Cowboy writes: Normally, the term "evolution" implicitly refers to super-long time frames. However, in the case of lizards on Florida islands, evolution seems to have shifted into a higher gear. Researchers have documented noticeable changes in a native species over a period of just 15 years, after an invading species altered their behavior (abstract). "After contact with the invasive species, the native lizards began perching higher in trees, and, generation after generation, their feet evolved to become better at gripping the thinner, smoother branches found higher up. The change occurred at an astonishing pace: Within a few months, native lizards had begun shifting to higher perches, and over the course of 15 years and 20 generations, their toe pads had become larger, with more sticky scales on their feet.

'We did predict that we'd see a change, but the degree and quickness with which they evolved was surprising,' said Yoel Stuart, a postdoctoral researcher in the Department of Integrative Biology at The University of Texas at Austin and lead author of the study... 'To put this shift in perspective, if human height were evolving as fast as these lizards' toes, the height of an average American man would increase from about 5 foot 9 inches today to about 6 foot 4 inches within 20 generations — an increase that would make the average U.S. male the height of an NBA shooting guard,' said Stuart."

Comments

Re:Falsifiability

[brunes69]

Discussion?

Evolution is easy to falsify. Apply pressure and see if the species DOES NOT adapt to the pressure.

If you believe that genes exist, then you believe in evolution, it's that simple. And if you don't believe that genes exist, then you might as well not believe in medicine either, or believe that cell phones exist, because it's all the same science.

Re:20 generations

[JaredOfEuropa]

If you kill the shortest third of all humans, the average height goes up immediately within the current generation.

Re:Falsifiability

[Artifakt]

It's not quite that simple, but you could probably simplify it to a few basic steps, like:
Is there a coding mechanism for heredity? - Yes, the genetic code.
Is there a way to generate new code? - Yes, mutation.
Does that code allow unlimited blending? - No, if it did the two sexes would completely blur together, among many other lesser examples.
Is there selection for fitness? - Yes, not everything gets to reproduce as much as it attempts to, and at least some of that is attributable to being "unfit".

Basically, people can point to examples where limited blurring may occur, or being taken out of the gene pool may have nothing to do with fitness (all dinosaurs are equally unfit to survive a 5 mile wide asteroid strike), or many other such factors, but they aren't really offering any effective criticism of evolution unless they want to claim things like selection or mutation never happen.

This is also why what Darwin did was science. His publication made several testable predictions - that there would be a genetic code, that the code could be altered on occasion, and that it would not allow unlimited blending of traits.

How is this surprising?

[ChrisK87]

I don't know why the researchers were so surprised by this. If the genetic variation already exists within the population under selective pressure, then the "evolution" measured by phenotypical changes in the population can take place literally overnight. Kill every human under 6'4" and the population will be 6'4" from then on, especially if you don't return to the set of selective pressures that had encouraged the shorter average. Sure there will be a lot of shorter individuals being born at first, but they'll fall to the same new selective pressure that killed the initial short cohort. This is exactly how the famous peppered moth evolution event happened so quickly; it wasn't anything unusual about the moth species in question, just a quick change in the suitability of existing genes. Evolution is only slow when the locally optimal genes don't exist in the population, and need to arise by mutation or genetic flow, or when an immediate optimum has room for genetic fine tuning, so to speak. TFA isn't really an example of evolution per se, it's an example of natural selection--a closely related concept in that they almost always co-occur, but it is not the same thing. We've changed the equilibrium frequencies of various genes, but as far as we know there are no new genes in this population. (And as far as that goes, it's a decent illustration of the importance of genetic diversity in a population: this population would be extirpated if it didn't have the genes responsible for these behavior and phenotype changes.)

Re:Is that unreasonable?

[ArcadeMan]

Twenty generations is enough for two people to repopulate large countries, or even the entire earth if they have large families.

That's probably why.