Tuesday, July 22, 2008

So here we go again...

Here we go again in Kansas, haggling about evolution. In the mean time evolution keeps on happening and in unexpected ways. For example, you may be familiar with the infectious cancer that is threatening the Tasmanian Devil (AKA Taz) with extinction. This cancer is spread when the Devils bite each other's faces during mating leading to spread of cancer cells from animal to animal.

The infectious cancer cells are genetically identical and their spread is believed to be made possible because inbreeding has led to a loss of genetic diversity so that the animal's immune systems are not able to recognize the foreign cancer cells.

See this link for background.

In an interesting twist, natural selection seems to be operating, at least in the short run, to favor precocious sexual activity and breeding. According to the research published in the Proceedings of the National Academy of Sciences, this is the first time where an infectious disease has been shown to bring about these sorts of life history changes in mammals.

Often times natural selection favors the spread of genes conferring increased resistance to a disease so the scientist's findings are some what surprising.

The other interesting thing is that even though genetic diversity in the Tasmanian Devil has apparently been reduced by genetic drift there is still enough genetic diversity for natural selection to lead to a rapid shift in the timing of reproduction.

Presumably the scientists will now follow up with research looking at the sorts of genes that are involved and try to related the life history changes they see to genetics. Might there also be long term responses in other aspects of the animal's behavior and physiology driven by natural selection?

Aside from it's implication for the survival of the Tasmanian Devil as a species, this research may provide insight into the ability of endangered species to evolutionarily adapt to rapid environmental changes be they due to disease or to human activity.

Meanwhile back in Kansas...sigh.

Cross posted with Dangerous Ideas.

Nota Bene:

Here is a very balanced discussion of the PNAS paper over at Not Rocket Science. Note in particular this comment:

"Jones clarifies that so far, all she has found is a physical response. Rather than reflecting genetic evolution, the changes in the devil's life cycle over such a short time span is almost certainly due to "phenotypic plasticity" - the ability of an organism to change its body and its behaviour to match its environment, without changing its genes."

So while there is clearly selective pressure for early reproduction, the immediate response of the population may be a physiological adaptation rather than a longer term evolutionary adaptation.




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