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In his fourth-floor lab at Harvard University, Michael Desai has created hundreds of identical worlds in order to watch evolution at work. Each of his meticulously controlled environments is home to a separate strain of baker’s yeast. Every 12 hours, Desai’s robot assistants pluck out the fastest-growing yeast in each world — selecting the fittest to live on — and discard the rest. Desai then monitors the strains as they evolve over the course of 500 generations. His experiment, which other scientists say is unprecedented in scale, seeks to gain insight into a question ( http://www.simonsfoundation.org/quanta/20140717-the-new-science-of-evolutionary-forecasting/ ) that has long bedeviled biologists: If we could start the world over again, would life evolve the same way ?
Many biologists argue that it would not, that chance mutations early in the evolutionary journey of a species will profoundly influence its fate. “If you replay the tape of life, you might have one initial mutation that takes you in a totally different direction,” Desai said, paraphrasing an idea first put forth by the biologist Stephen Jay Gould in the 1980s.
Desai’s yeast cells call this belief into question. According to results published in Science in June ( http://www.ncbi.nlm.nih.gov/pubmed/24970088 ), all of Desai’s yeast varieties arrived at roughly the same evolutionary endpoint (as measured by their ability to grow under specific lab conditions) regardless of which precise genetic path each strain took. It’s as if 100 New York City taxis agreed to take separate highways in a race to the Pacific Ocean, and 50 hours later they all converged at the Santa Monica pier.
http://www.wired.com/2014/10/evolution-paths-fitness/
(Score: 4, Informative) by HiThere on Saturday October 04 2014, @06:53PM
One reason is the tse-tse fly.
Seriously, think of humans as an invasive species. When they leave the area in which they've evolved, they leave behind the predators that have evolved together with them. Bears are dangerous, but they don't compare with leopards, when all you've got is a thrusting spear.
Then there's sleeping sickness, malaria, Ebola, etc. There are good reasons why Africa used to be called "the white man's graveyard" and they don't have much to do with the human inhabitants. It wasn't only the graveyard of white men, but the natives didn't get the same press.
That said, there's reasonable evidence that Africa is one of the places that discovered refining iron. So to claim that they've always been stuck in a valley is unfair. For that matter, Egypt is one of the ancestral civilizations. And Ethiopia was a strong enough country to keep them from expanding to the south (or we'd have had coffee a lot earlier).
Javascript is what you use to allow unknown third parties to run software you have no idea about on your computer.