A classic example of evolution in action has just been identified.
Deer mice living on the sand hills of Nabraska have gone for a new colour in their hair. The sand hills have a distinctive colouration compared to the soil around them and these mice have evolved to blend in. Seeing as the sand hills are relatively recent – possibly only 8000 years old – this adaptation to evade predators has occurred reasonably quickly.
What’s really clever about this research is that it has worked out the genetic mechanism that has brought it about. The light colour is all due to the amount of pheomelanin in the hair. The gene largely responsible for pheomelanin is called Agouti. The researchers noticed in the laboratory that in the pale mice there were 7 differences in the coding area of the gene when compared with the darker mice. These changes lead to 2 differences in the amino acids that are produced (genes are codes that programme sequences of amino acids that in turn are built together into proteins). On closer examination in the wild it was found that one of these changes (a serine deletion) was responsible for the paler colour.
The beauty of this is that it demonstrates the whole process of evolution so neatly. We have a random genetic mutation producing a real survival benefit. Natural selection has seen to it that this change has been able to sweep through the whole population of mice in those sand hils.
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Interesting if not a little Lamarckian in theory depending how you look at it I guess!
ReplyDeleteHow is that Lamarkian?
ReplyDeleteOn first read the original article looked like it was arguing that the mice changed fur colour to suit their environment - a fundamental element of Lamarckian Theory -
ReplyDelete1. Use and disuse – Individuals lose characteristics they do not require (or use) and develop characteristics that are useful.
2. Inheritance of acquired traits – Individuals inherit the traits of their ancestors.
I think the way Charles highlighted it: "Deer mice living on the sand hills of Nabraska have gone for a new colour in their hair. The sand hills have a distinctive colouration compared to the soil around them and these mice have evolved to blend in." nods in the Lamarck direction.
Also the original abstract says ' Furthermore, our data suggest that this derived Agouti allele arose de novo after the formation of the Sand Hills.' Again, on first read suggesting the mice changed in response to the environment (Lamarck) not that they survived better because of a random (fortunately advantageous) mutation!
If it is argued in Darwinian language, it would be more along the lines of "...mice living on the sand hills... now blend in better with their environment as the mice with the other colour hair have been picked off by predators."
Charles clears it up in his last paragraph and puts it in accepted natural selection - survival of the fittest / best adapted terms but the earlier section threw me initially.