I have blogged about the genetics of altitude adaptation before. There seem to be three populations in the world which have been subject to very strong natural selection, resulting in physiological differences, in response to the human tendency toward hypoxia. Two of them are relatively well known, the Tibetans and the indigenous people of the Andes. But the highlanders of Ethiopia have been less well studied, nor have they received as much attention. But the capital of Ethiopia, Addis Ababa, is nearly 8,000 feet above sea level!
Another interesting aspect to this phenomenon is that it looks like the three populations respond to adaptive pressures differently. Their physiological response varies. And the more recent work in genomics implies that though there are similarities between the Asian and American populations, there are also differences. This illustrates the evolutionary principle of convergence, where different populations approach the same phenotypic optimum, though by somewhat different means. To my knowledge there has not been as much investigation of the African example. Until now. A new provisional paper in Genome Biology is out, Genetic adaptation to high altitude in the Ethiopian highlands:
One of the great geological landmarks on earth are the Himalayas. Not only are the Himalayas of importance in the domain of physical geography, but they are important in human geography as well. Just as South Asians and non-South Asians agree that the valley of the Indus and its tributaries bound the west of the Indian cultural world, so the Himalayas bound it on the north. Unlike many pre-modern constructions, such as the eastern boundary of Europe, the northern limit of South Asia is relatively clear and distinct. It is stark on a relief map; the flat Gangetic plain gives way to mountains. And it is stark a cultural map, the languages of northern India give way to those of the world of Tibet. The religion of northern India gives way to the Buddhism of Tibet. In terms of human geography I believe that one can argue that the Himalayan fringe around South Asia exhibits the greatest change of ancestrally informative gene frequencies over the smallest distance when you exclude those regions separated by water barriers. Unlike the Sahara the transect from the northern India to Chinese Tibet at any given point along the border is permanently inhabited, albeit sparsely at the heights.
And yet despite the geographical barriers people and ideas did move across the Himalaya. The cultural influences upon Tibet from India are obvious. The script of Tibet is derived from India, while its form of Buddhism is the direct descendant of the last efflorescence of that religion in northern India. But while culture moved north, I do not see much evidence genetically that South Asians have been significant as an influence. This is somewhat shocking when you realize these two facts: the population of the Tibetan Autonomous Region is on the order of 5-6 million, while that of northern South Asia around ~1 billion (including Pakistan and Bangladesh). A 200-fold difference. And yet there is evidence of admixture between the two groups exactly where you’d expect: in Nepal. Below is a figure from a recent paper which shows how South and East Asian populations relate to each other. I’ve highlighted the Nepali groups, which span the two larger classes:
You probably are aware that different populations have different tolerances for high altitudes. Himalayan sherpas aren’t useful just because they have skills derived from their culture, they’re actually rather well adapted to high altitudes because of their biology. Additionally, different groups seem to have adapted to higher altitudes independently, exhibiting convergent evolution. But in terms of physiological function they aren’t all created equal, at least in relation to the solutions which they’ve come to to make functioning at high altitudes bearable. In particular, it seems that the adaptations of the peoples of Tibet are superior than those of the peoples of the Andes. Superior in that the Andean solution is more brute force than the Tibetan one, producing greater side effects, such as lower birth weight in infants (and so higher mortality and lower fitness).
The Andean region today is dominated by indigenous people, and Spanish is not the lingua franca of the highlands as it is everyone in in the former colonial domains of Spain in the New World. This is largely a function of biology; as in the lowlands of South America the Andean peoples were decimated by disease upon first contact (plague was spreading across the Inca Empire when Pizzaro arrived with his soldiers). But unlike the lowland societies the Andeans had nature on their side: people of mixed or European ancestry are less well adapted to high altitudes and women without tolerance of the environment still have higher miscarriage rates.