PsyPost reports:

By analyzing the genetic material of thousands of ancient humans, researchers have mapped how natural selection influenced hundreds of physical and behavioral traits across West Eurasia over the past 10,000 years. The findings reveal that evolution continuously pushed specific genetic variations to become more or less common, affecting everything from blood type to disease risk. The study was published in Nature.

Evolution is driven by multiple forces, but one of the most recognizable is directional selection. This happens when a specific genetic mutation provides a survival or reproductive advantage, causing it to become increasingly common in a population. Conversely, a disadvantageous trait will be driven out of the population over successive generations.

Tracking this process in humans has proven highly difficult for geneticists. As human populations migrated, conquered, and mixed over thousands of years, the frequencies of certain genes shifted naturally. This natural, random fluctuation is known as genetic drift. It is hard for researchers to separate random genetic drift from genuine directional selection. For a long time, scientists could not easily tell if a gene became common because it was highly advantageous or simply because a migrating group of people happened to carry it.

A team of researchers led by Ali Akbari, a geneticist at Harvard Medical School, sought to solve this problem. They developed a new statistical method designed to track genetic changes over thousands of years and separate the effects of human migration from genuine evolutionary pressure.

The researchers gathered a massive dataset of genetic material from 15,836 ancient individuals who lived in West Eurasia. This geographic area includes Europe and neighboring parts of the Near East. The skeletal remains spanned a timeframe of 18,000 years. The team sequenced over 10,000 of these genomes for the first time, vastly expanding the available data for ancient human genetics.

Using their new statistical approach, the group examined nearly ten million distinct points in the human genome. They looked for consistent trends where a specific gene became steadily more or less common across different populations and eras. The immense sample size allowed them to spot subtle evolutionary nudges that earlier studies lacked the statistical power to definitively detect.

They found that directional selection has been incredibly common in West Eurasia over the past ten millennia. The team identified hundreds of specific genetic variants that were either favored or actively weeded out by evolutionary forces. Many of these genes are linked to the human immune system and the body’s response to changing diets. [Continue reading…]