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 70–80% 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 prion caused 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 altitudes, 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, increasing their capacity for carrying oxygen. This mutation is believed to be around 3,000 years old. 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 oxygen-carrying red blood cells. Over time, individuals with larger spleens were more likely to survive the lengthy free-dives, and thus reproduce. By contrast, communities centered around farming show no signs of evolving to have larger spleens. Because the Sama-Bajau show no interest in abandoning this lifestyle, there is no reason to believe further adaptation will not occur. Advances in the biology of genomes have enabled geneticists to investigate the course of human evolution within centuries. Jonathan Pritchard and a postdoctoral fellow, Yair Field, counted the singletons, or changes of single DNA bases, which are likely to be recent because they are rare and have not spread throughout the population. Since alleles bring neighboring DNA regions with them as they move around the genome, the number of singletons can be used to roughly estimate how quickly the allele has changed its frequency. This approach can unveil evolution within the last 2,000 years or a hundred human generations. Armed with this technique and data from the UK10K project, Pritchard and his team found that alleles for lactase persistence, blond hair, and blue eyes have spread rapidly among Britons within the last two millennia