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Caught In The Act?

Some rapidly evolving lizards have been discovered on an Adriatic island:

The transplanted lizards adapted to their new environment in ways that expedited their evolution physically, Irschick explained.

Pod Mrcaru, for example, had an abundance of plants for the primarily insect-eating lizards to munch on. Physically, however, the lizards were not built to digest a vegetarian diet.

Researchers found that the lizards developed cecal valves--muscles between the large and small intestine--that slowed down food digestion in fermenting chambers, which allowed their bodies to process the vegetation's cellulose into volatile fatty acids.

"They evolved an expanded gut to allow them to process these leaves," Irschick said, adding it was something that had not been documented before. "This was a brand-new structure."

Along with the ability to digest plants came the ability to bite harder, powered by a head that had grown longer and wider.

It will be interesting to see not only if there is a genetic basis for this change, but if they can still interbreed with the original species. If not, that's called a "new species," folks.


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plutosdad wrote:

I wonder if the instructions for creating those valves were already present, like how some species can switch sex if they are put in an environment with all of one sex. Perhaps the lizards have a similar "switch" that goes off if it is eating too many vegetables.

Only way to tell would be to re-introduce some more lizards and then a few years later find them (not their offspring but the same ones) and see if any new structures have grown.

If that were true, well that would be a pretty amazing find too, but for different reasons.

David wrote:

This article gets to the nub of my problem with evolution (at least the way it is taught in Japan, for example) - the only thing we know for sure is that evolution as understood today is wrong! People go around saying the "evolution kill god", and basing morality on evolution when we don't (and never really will) completely understand evolution - we certainly don't know enough to go around calling others idiots...

(That said, I think evolution is closer to the truth than "intelligent design" as the hardliners preach it - and I have no desire to see a movie made about these lizards.)

This "fast evolution" is exactly what I thought was more likely. I really hope they can discover the mechanism - I still think that genetics has less to do with mutation then most people think. For example, I would not be surprised if evolution happened in multiple organisms in parallel, rather than having a single organism responsible for the change.

David A. Young wrote:

Yes, the "nominal" explanation for evolution (as I was taught it) -- random mutation -- seems entirely inadequate to explain this type of rapid evolution, especially with such a small initial population. I have no idea what the missing pieces of the puzzle are, but I'm willing to bet the eventual answers will jump right over "interesting" straight to "fascinating, captain."

Paul F. Dietz wrote:

Yes, the "nominal" explanation for evolution (as I was taught it) -- random mutation -- seems entirely inadequate to explain this type of rapid evolution

You had bad teachers. Selection on existing variation is as important as, if not more important than, new mutations. And much variation comes from recombination during sexual reproduction, not new mutation.

Lee Valentine wrote:

Paul is correct. Your teachers did not understand evolution. Then again, almost no one does.

Evolution is quantitative.
The problem is that there are few established coefficients.

Karl Hallowell wrote:

Actually I see this as an expected outcome for evolution. Rapid generation change occurs because first, we see a population bottleneck and second, strong and different selection than the old population had been subject to. Finally, this came from a population of ten individuals. So it has interesting implications for what makes up a minimum population of a viable gene pool.

Brock wrote:

The key quote for Rand's point is:

"What could be debated, however, is how those changes are interpreted—whether or not they had a genetic basis and not a "plastic response to the environment," said Hendry, who was not associated with the study."

Changes to the diet and environment could have changed the gene expression of the epigenome without changing the genome itself. It's perfectly possible that these lizards are 100% the same (at the DNA level) as the lizards introduced in the '70s, but with different genes being expressed.

Habitat Hermit wrote:

Rand it's extremely unlikely that a change such as the one described would make breeding between the variations impossible.

The comparison made by one of the Italians that this would be equal to a human growing another appendix seems like an exaggeration but even if it isn't a human with an extra appendix would still be able to breed with other humans.

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This page contains a single entry by Rand Simberg published on April 23, 2008 7:14 AM.

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