The latest research into ancient human DNA reveals that our evolution has sped up significantly over the last 10,000 years. This study, led by David Reich from Harvard Medical School, analyzed the genetic makeup of over 15,000 ancient humans from Europe and the Middle East. They discovered hundreds of gene variants that changed due to natural selection, especially after agriculture started.
Reich mentions, “We are seeing dramatic changes.” However, some experts are skeptical about how much these gene changes impact complex traits like mental health and intelligence.
When Homo sapiens appeared in Africa about 200,000 to 300,000 years ago, they began to spread worldwide. The shift to farming brought new foods and diseases, making human gatherings larger and closer to animals. This transition required significant genetic adaptation.
Previously, research only uncovered a few genetic markers that signified natural selection. The best-known example is the gene variant that allows many Europeans to digest lactose, the sugar in milk, into adulthood.
Reich and his team gathered a wealth of ancient genomic data, aiming to pinpoint gene variants that were either rising in frequency because they were beneficial or declining due to being harmful. They found 479 variants showing strong evidence of selection. The data showed that as humanity shifted from hunter-gatherer lifestyles to more settled agricultural ones, our biological makeup was also changing.
Interestingly, the research established that evolution accelerated during the Bronze Age, which began around 5,000 years ago. This may reflect deeper lifestyle changes kickstarted by the onset of farming.
The team’s method focused on tracking consistent changes in gene frequency across various populations over time. While many gene frequencies fluctuated, some traits clearly left an impression on our biology. For instance, a variant linked to a higher risk of multiple sclerosis surged around 6,000 years ago but then became less common in more recent European groups.
Moreover, genes related to immunity showed strong signs of natural selection. One variant associated with tuberculosis susceptibility decreased in frequency over the last 3,000 years, likely due to changing disease environments. A gene that provides resistance to HIV became more frequent between 6,000 and 2,000 years ago, potentially offering protection against plagues as well.
Evolution also impacted physical characteristics. The study identified ten variants associated with lighter skin tones that had positive selection signals. Furthermore, a gene responsible for male pattern baldness decreased in frequency over the last 7,000 years, leading to a modest decline in baldness prevalence.
The insights from this study paint a compelling picture of human adaptability. With agriculture and social organization arising, our DNA has been in constant flux, shaping not only our health but also our physical traits. By exploring these ancient genomes, we gain a deeper understanding of our past and how it continues to influence us today.
For more on this topic, you can read a related article from Nature.
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Evolution,Genetics,Science,Humanities and Social Sciences,multidisciplinary
