page_title: Recent human evolution
section_title: Upper Paleolithic, or the Late Stone Age (50,000 to 12,000 years ago)
hierarchical_section_title: Recent human evolution / Upper Paleolithic, or the Late Stone Age (50,000 to 12,000 years ago)
caption_attribution_description: English: This image was cropped from a California government photo of Leland Y. Yee, Speaker pro tempore, California State Assembly, shown here: [1]. California State government photos are in the public domain.
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: DNA analyses conducted since 2007 revealed the acceleration of evolution with regards to defenses against disease, skin color, nose shapes, hair color and type, and body shape since about 40,000 years ago, continuing a trend of active selection since humans emigrated from Africa 100,000 years ago. Humans living in colder climates tend to be more heavily built compared to those in warmer climates because having a smaller surface area compared to volume makes it easier to retain heat. People from warmer climates tend to have thicker lips, which have large surface areas, enabling them to keep cool. With regards to nose shapes, humans residing in hot and dry places tend to have narrow and protruding noses in order to reduce loss of moisture. Humans living in hot and humid places tend to have flat and broad noses that moisturizes inhaled hair and retains moisture from exhaled air. Humans dwelling in cold and dry places tend to have small, narrow, and long noses in order to warm and moisturize inhaled air. As for hair types, humans from regions with colder climates tend to have straight hair so that the head and neck are kept warm. Straight hair also allows cool moisture to quickly fall off the head. On the other hand, tight and curly hair increases the exposed areas of the scalp, easing the evaporation of sweat and allowing heat to be radiated away while keeping itself off the neck and shoulders. Epicanthic eye folds are believed to be an adaptation protecting the eye from the snow and reduces snow glare.
  Physiological or phenotypical changes have been traced to Upper Paleolithic mutations, such as the East Asian variant of the EDAR gene, dated to about 35,000 years ago. Traits affected by the mutation are sweat glands, teeth, hair thickness and breast tissue. While Africans and Europeans carry the ancestral version of the gene, most East Asians have the mutated version. By testing the gene on mice, Yana G. Kamberov and Pardis C. Sabeti and their colleagues at the Broad Institute found that the mutated version brings thicker hair shafts, more sweat glands, and less breast tissue. East Asian women are known for having comparatively small breasts and East Asians in general tend to have thick hair. The research team calculated that this gene originated in Southern China, which was warm and humid, meaning having more sweat glands would be advantageous to the hunter-gatherers who lived there. Geneticist Joshua Akey suggested that the mutant gene could also be favored by sexual selection in that the visible traits associated with this gene made the individual carrying it more attractive to potential mates. Yet a third explanation is offered by Kamberov, who argued that each of the trait due to the mutant gene could be favored at different times. Today, the mutant version of EDAR can be found among 93% of the Han Chinese, 70% among the Japanese and the Thai, and between 60% to 90% among the American Indians, who descended from East Asia.
  The most recent Ice Age peaked in intensity between 19,000 and 25,000 years ago and ended about 12,000 years ago. As the glaciers that once covered Scandinavia all the way down to Northern France retreated, humans began returning to Northern Europe from the Southwest, modern-day Spain. But about 14,000 years ago, humans from Southeastern Europe, especially Greece and Turkey, began migrating to the rest of the continent, displacing the first group of humans. Analysis of genomic data revealed that all Europeans since 37,000 years ago have descended from a single founding population that survived the Ice Age, with specimens found in various parts of the continent, such as Belgium. Although this human population got displaced 33,000 years ago, a genetically related group began spreading across Europe 19,000 years ago. Recent divergence of Eurasian lineages was sped up significantly during the Last Glacial Maximum, the Mesolithic and the Neolithic, due to increased selection pressures and founder effects associated with migration. Alleles predictive of light skin have been found in Neanderthals, but the 
caption: Epicanthic eye folds are thought to be an adaptation for cold weather.
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