Evolution Claims

I again came across the claim of "observed evolution" regarding the Italian Wall Lizards of Pod Mrcaru Island. I thought I had addressed this years ago, but I didn't find it, so I'll repeat the process.

These lizards are not indigenous to the island and were introduced 36 years ago. In 2008, a paper was released regarding a study of the lizard, and its changes from the "ancestral population". Most of the changes were morphological, involving the shape of head and jaw, with some changes in social habits too. But the most striking claim is that the lizards had developed a new feature: a cecal valve in their digestive tract, which did not exist in the ancestral population. The cecal valve has utility because it allows the slowing of digestion, which is needed to accommodate the increase in the vegetative proportion of the diet. According to the paper,

"The relatively large fraction of leaves included into the diet of
lizards in the introduced population of Pod Mrcaru has apparently
also resulted in the evolution of cecal valves, a structure
previously unreported for this species and rare in this family and
scleroglossan lizards in general" (13, 14, 18).

Since this occurred in roughly 30 generations, it is being referred to as rapid evolution. And being an apparently new organic type feature, many internet evolution apologists seem to accept this as having evolved and being absolute proof of "observed evolution". However, this blatantly ignores other possibilities, chief among which is that the gene for the cecal valve pre-existed and was turned off by negative mutation during disuse of the feature.

This could be supported or falsified by finding the differences in DNA between the Pod Mrcaru population and its ancestral population, and determining if the gene is novel, or if it is previously there, but turned off.

I contacted an author of the paper, Dr. Duncan J. Irschick, to ask if the DNA testing had been done to determine the genetic source of the cecal valve. Dr. Irschick replied, "not yet!"

That seems to put closure on the current claim: it is not known if the "new feature" is actually new, or if it pre-existed in an OFF state, even 6 years later. The fact that a tiny percentage of close relatives do have the feature suggests that the feature might have been necessary prehistorically, but was shut off as the lizard's environment shifted toward high populations of insects, relieving the need for plant matter. Parsimony suggests that the valve did not evolve from nothing in 30 generations, especially given a more likely source.

Whenever an evolution claim is made, always track down what is actually known. So far it does not include new physical organs.

ADDENDUM:
I received this message from Dr. Anthony Herrel

Hi,

We're still working on getting a handle on those questions. We are
currently analyzing the microbial communities in the lizards from the
two islands. A next step will be to raise lizards from the two islands
in a common environment to test whether the presence of the cecal
valves is genetic or not. Once we have understood these elements we
can then ask the question pertaining to the underlying molecular
mechanisms.

Sorry for not being able to address your question yet, but we're
working on it.

Anthony

The response from these authors has been rapid, kind and polite. While I'm not sure why the molecular analysis must wait on the outcome of these tests, it will be interesting to see what they produce.