EvC Forum: Rapid Evolution in Lizards

Last month, the PNAS published a remarkable study of evolution in action.

The abstract can be found here.

And a short summary can be found here or here.

The original paper is really quite brief (and under lock and key) but the summaries are very thorough, especially Pharyngula's, so you can get a pretty good idea of what the paper says.

A population of 10 lizards, Podarcis sicula, were released by scientists on an Adriatic island, Pod Mrcaru, back in 1971. The scientists weren't able to return to the island for 36 years, but when they did, they found that the lizard population had evolved an entirely new phenotypic feature: a cecal valve.

Have a look!

RAZD once said:

The purpose is to get a creationist definition of what "large scale change" is -- it is their criteria.

In only 30 generations, these lizards grew a new body part in response to environmental pressures. They were insectivores, but evolved into herbivores ... a cecal valve is necessary for digesting cellulose.

To quote Pharyngula:

Now here's something really cool, though: these lizards have evolved cecal valves. What those are are muscular ridges in the gut that allow the animal to close off sections of the tube to slow the progress of food through them, and to act as fermentation chambers where plant material can be broken down by commensal organisms like bacteria and nematodes ” and the guts of Pod Mrcaru P. sicula are swarming with nematodes not found in the guts of their Pod Kopiste cousins.

Photographs illustrating the cecal valves in a male (A), a female (B), and a hatchling (C) P. sicula from Pod Mrcaru. Note the thick cecal wall and pronounced ridges. The arrow in C indicates the position of the cecal valve in a hatchling as seen from the outside.

This is more than a simple quantitative change, but is actually an observed qualitative change in a population, the appearance of a new morphological structure.

One of the authors of the paper commented:

Such physical transformation in just 30 lizard generations takes evolution to a whole new level, Irschick said.

"It would be akin to humans evolving and growing a new appendix in several hundred years."

"That's unparalleled. What's most important is how fast this is," he said.

It is easy to see how such changes, accumulating over millions of years, can lead to the evolution of entirely different species.

Body part + body part + ... = new critter.

I would love to hear what our resident "microevolution" v. "macroevolution" enthusiasts think.

Edited by molbiogirl, : No reason given.

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