page_title: Recent human evolution
section_title: Bronze Age to Medieval Era
hierarchical_section_title: Recent human evolution / Holocene (12,000 years ago till present) / Bronze Age to Medieval Era
caption_attribution_description: Philippinen Basilan Seezigeuner
context_page_description: Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within Homo sapiens populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster than ever before. It is possible that human culture—itself a selective force—has accelerated human evolution. With a sufficiently large data set and modern research methods, scientists can study the changes in the frequency of an allele occurring in a tiny subset of the population over a single lifetime, the shortest meaningful time scale in evolution. Comparing a given gene with that of other species enables geneticists to determine whether it is rapidly evolving in humans alone. For example, while human DNA is on average 98% identical to chimp DNA, the so-called Human Accelerated Region 1, involved in the development of the brain, is only 85% similar.
context_section_description: Resistance to malaria is a well-known example of recent human evolution. This disease attacks humans early in life. Thus humans who are resistant enjoy a higher chance of surviving and reproducing. While humans have evolved multiple defenses against malaria, sickle cell anemia—a condition in which red blood cells are deformed into sickle shapes, thereby restricting blood flow—is perhaps the best known. Sickle cell anemia makes it more difficult to the malarial parasite to infect red blood cells. This mechanism of defense against malaria emerged independently in Africa and in Pakistan and India and within the last 4,000 years or so, has spread to between 10% and 15% of the populations of these places. Another mutation that enabled humans to resist malaria that is strongly favored by natural selection and has spread rapidly in Africa is the inability of synthesize the enzyme glucose-6-phosphate dehydrogenase, or G6PD.
  A combination of poor sanitation and high population densities proved ideal for the spread of contagious diseases which was deadly for the residents of ancient cities. Evolutionary thinking would suggest that people living in places with long-standing urbanization dating back millennia have evolved resistance to certain diseases, such as tuberculosis and leprosy. Using DNA analysis and archeological findings, scientists from the University College London and the Royal Holloway studied samples from 17 sites in Europe, Asia, and Africa. They learned that indeed, long-term exposure to pathogens has led to resistance spreading across urban populations as people pass these traits onto their descendants. Urbanization is therefore a selective force that has influenced human evolution. The allele in question is named SLC11A1 1729+55del4. Scientists found that among the residents of places that have been settled for thousands of years, such as Susa in Iran, this allele is ubiquitous whereas in places with just a few centuries of urbanization, such as Yakutsk in Siberia, only 70% to 80% of the population have it.
  Adaptations have also been found in modern populations living in extreme climatic conditions such as the Arctic, as well as immunological adaptations such as resistance against brain disease in populations practicing mortuary cannibalism, or the consumption of human corpses. Inuit have the ability to thrive on the lipid-rich diets consisting of Arctic mammals. Human populations living in regions of high attitudes, such as the Tibetan Plateau, Ethiopia, and the Andes, benefit from a mutation that enhances the concentration of oxygen in their blood. This is achieved by having more capillaries in their cells, which increases the capacity for carrying oxygen. This mutation is believed to be around 3,000 years old.
  Geneticist Ryosuke Kimura and his team at the Tokai University School of Medicine discovered that an allele called EDAR, practically absent among Europeans and Africans but common among East Asians, gives rise to thicker hair, presumably as an adaptation to the cold. Kohichiro Yoshihura and his team at Nagasaki University found that a variant of the gene ABCC11 produces dry ear wax among East Asians. Africans and Europeans by contrast share the older version of the gene, producing wet ear wax. However, it is not known what evolutionary advantage, if any, wet ear wax confers, so this variant was likely selected for some other trait, such as making people sweat less. What scientists do know, however, is that dry ear wax is strongly favored by natural selection in East Asia.
  A recent adaptation has been proposed for the Austronesian Sama-Bajau, also known as the Sea Gypsies or Sea Nomads, developed under selection pressures associated with subsisting on free-diving over the past thousand years or so. As maritime hunter-gatherers, the ability to dive for long periods of times plays a crucial role in their survival. Due to the mammalian dive reflex, the spleen contracts when the mammal dives and releases the oxygen-carrying red blood cells. Over time, individuals with larger spleens were more likely to surviv
caption: The Sama-Bajau have evolved to become durable free divers.
exif: {}