Tuesday, July 03, 2007

Human evolution in perspective

Evolution keeps fascinating me. The earth is 4.5 billion years old, life on earth began 3.8 billion years ago, and the homo genus is only 2 million years old. The species Homo Sapiens is only about 250,000 years old, but only left Africa about 80 – 100,000 years ago. (Take a walk through Wikipedia articles on Homo Sapiens, human evolution, geologic time, and the single origin hypothesis.)

(There’s also the proposition that there was a human bottleneck about 70,000 years ago, which reduced the population of breeding pairs to between 1,000 and 10,000 – see the Homo Sapiens article – which is postulated to be due to the mammoth Toba volcanic eruption.)
The serious point here is that these changes are dramatically exponential, rather than linear.

A recent article on continuing evolution mentions a few other interesting facts, inter alia. For instance, that lactose tolerance emerged among European cattle herders only about 5,000 years ago.

It also mentions a genomic survey five years ago that found people were clustered on the basis of small DNA changes into five groups, roughly corresponding to the continents: Africans, Australian Aborigines, East Asians, American Indians, and Caucasians. That latter group includes everyone from Europe to India, including the Middle East.

I would add more recent changes that have a lasting effect on the population, such as the constant plagues in Europe in the middle ages, which had a dramatic impact on the population, and undoubtedly divided the genetic pool.

Ye The domination of dinosaurs prevented mammal expansion beyond the size of a shrew, but a chance meteor impact cleared away the larger animals that couldn't burrow or hide, and left the planet empty enough for the speciation of those who could.  And there's the Homo genus Neanderthal, which died out despite a larger brain capacity than us.

Species domination is not necessarily about being the "best and brightest": it’s about what survives the particular environments of the time.
...which doesn't bode well for us, if we're now powerful enough to destroy our own evolutionary niche, our environment.

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