how natural selection still affects humans
As we’ve seen before, the cliche that humans aren’t evolving in any meaningful way are completely untrue and in reality, we’re actually evolving faster than ever thanks to our skyrocketing populations. But what about a tangential truism regarding natural selection? Is our use of advanced technology effectively circumventing this process for our species? After all, predation is hardly widespread nowadays, and many human shortcomings are dealt with by innovation. So what possible natural selection could be going on with a species so reliant on technology to solve its problems? Well, over the last few days, social bookmarking sites were heavily to one example of how nature is still shaping humans by evolution and illustrating all its quirks and inefficiencies.
Humans originally evolved close to sea level and as a result, life at very high altitudes can be rather difficult for us since we have trouble getting enough oxygen into our bodies. At an elevation of roughly 4,000 meters, just above 13,000 ft., most of us would experience altitude sickness and have trouble just being at those heights. But for Tibetans who live on those soaring plateaus, this is home sweet home and they’re well adapted to the altitudes thanks to the forces of natural selection which promoted the expression of the EPAS1 gene, a gene involved in red blood cell production and it’s overexpression in 87% of Tibetans allows the local populations to keep their blood cell counts down while doing much more with the oxygen in their bodies. In a span of just 2,750 years, Tibetans effectively evolved to be much more efficient in metabolizing oxygen because of EPAS1 mutations, which were an advantage at extremely high altitudes.
But that’s not all. The Tibetans aren’t the only high altitude dwellers around, and in South America, the people who live high in the Andes are dealing with the same problem. Now, since Tibet is the most remote place on the planet and it’s difficult to simply incorporate their EPAS1 mutation the good, old fashioned way, the Andes’ mountain dwellers evolved a different solution. Humans who evolved at sea levels will simply generate more red blood cells to absorb more oxygen, compensating for higher altitudes. In the Peruvian Andes, that’s what happens to the local residents. They simply have an elevated blood cell count to counter the effects of having less oxygen to absorb into their tissues. The same species living in geographical isolation evolving two rather different adaptations to the same kinds of environments. Sounds an awful lot like the effects of evolution in full swing and affecting human capabilities for survival by indirectly promoting beneficial mutations. It might not be as dramatic as evolving camouflage to escape predators, but it’s still pretty significant.
