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People in denial about evolution often ask why humans aren’t still evolving; even some who accept the reality of evolution wonder about this. In fact humans do continue to evolve, and can do so at fairly rapid rates. The best example might be the evolution of resistance of kuru in the Fore tribe of Papua New Guinea. Kuru is similar to Creutzfeldt-Jakob disease, and is acquired through consuming human brains, something done by the Fore because they believed that they should consume all of the body of loved ones who die.
[caption id=”attachment_626” align=”aligncenter” width=”200” caption=”Human Evolution - Skulls NYT / Getty”][/caption]
Kuru could have destroyed the Fore tribe, but a single mutation in a single woman just 200 years ago spread widely, providing resistance until cannibalism was outlawed.
[quote]The emergence of kuru resistance is one of the clearest examples of very rapid human evolution but it is far from the only one. Around 3000 years ago, the ancestors of Tibetans split from the population that gave rise to the Han people of China. As soon as they began living at altitude, the population began to adapt. While some of the adaptations are a result of living in the mountains - a bit like altitude training in athletes - some are genetic.
One variant in a gene controlling the production of red blood cells, for instance, is found in 78 per cent of Tibetans but just 9 per cent of Han people. And the process has not stopped. “We think the selection process is ongoing,” says Rasmus Nielsen of the University of California, Berkeley, who led the study (Science, vol 329, p 75).
More evidence comes from a study of Tibetan women living above 4000 metres. Those with high levels of oxygen in the blood had 3.6 surviving children on average, whereas those with low oxygen levels had just 1.6, due to much higher infant mortality. That suggests the genetic variant thought to be responsible for higher blood oxygen levels is being passed on in greater numbers and becoming more common (Proceedings of the National Academy of Sciences, vol 101, p 14300).
Source: New Scientist, April 2, 2011[/quote]These might not seem like especially dramatic examples of human evolution, but there is no doubt that they are evolution in action. They key in examples like this is the presence of some sort of selective, environmental pressure. There won’t really be any evolution without some sort of pressure from the environment — something that creates competition between individuals with slightly different genes.
Read more: About.com