Saturday, July 26, 2014

My Year of Darwin: 7/26/2014 The importance of geographic isolation

 Charles Darwin

"I cannot give my reasons in detail: but the most general conclusion, which the geographical distribution of all organic beings, appears to me indicate, is that isolation is the chief concomitant or cause of the appearance of new forms (I well know there are some staring exceptions)." Charles Darwin, Letter to colleague J.D. Hooker, 8 September 1844

This is was an element of Darwin's theory that I don't remember the importance of geographic isolation being stated so strongly. After I finish his autobiography and this small collection of letters, I plan on going through Origin on Species (for the 4th time). 

Darwin's hypothesis is this: a population becomes divided into two populations. Should conditions change (as they inevitably will), species adapt to those condition. If conditions are different between populations, then species will become (phenotypically) different. 

I'm totally down with that. I think the modern view is that populations that are isolated will evolve to be different species even if conditions are identical - genetic drift driving the divergence. Species must evolve. 

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