Researchers have discovered that the duplication of a gene, called the salivary amylase gene (AMY1), may have helped early humans digest starch more effectively. This adaptation likely emerged long before humans began farming and consuming large quantities of starchy foods like bread and pasta. The study, published in 'Science', explains that the more copies of the AMY1 gene a person has, the more enzyme amylase they can produce, improving their ability to break down starch into glucose.
"The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest effectively," said Omer Gokcumen, PhD, a professor at the University at Buffalo and the study's corresponding author. Amylase is responsible not only for breaking down starch but also for contributing to the flavor of bread.
Using advanced genetic mapping techniques, the team uncovered that AMY1 gene duplications date back to at least 800,000 years ago, affecting both early humans and Neanderthals. "This suggests that the AMY1 gene may have first duplicated more than 800,000 years ago, well before humans split from Neanderthals and much further back than previously thought," said Kwondo Kim, a lead author of the study from JAX.
The study examined ancient human genomes and found that even pre-agricultural hunter-gatherers had an average of four to eight AMY1 copies per diploid cell. This genetic diversity indicates that the capacity to digest starch was already well-established long before the advent of farming.
The research also sheds light on how agriculture further influenced AMY1 variation. Over the past 4,000 years, as starch consumption increased in Europe, so did the average number of AMY1 copies in the population. Gokcumen's previous studies demonstrated that domesticated animals living alongside humans, such as dogs and pigs, also evolved to have higher amylase gene copies, adapting to starch-heavy diets.
"Individuals with higher AMY1 copy numbers were likely digesting starch more efficiently and having more offspring," Gokcumen explained. "Their lineages ultimately fared better over a long evolutionary timeframe than those with lower copy numbers."
The study's findings align with other recent research, such as a University of California, Berkeley-led study that found the average number of AMY1 copies in Europe increased from four to seven over the last 12,000 years.
Feyza Yilmaz, a computational scientist at JAX and co-author of the study, emphasized the importance of AMY1 gene variation in human evolution. "This genetic variation presents an exciting opportunity to explore its impact on metabolic health and uncover the mechanisms involved in starch digestion and glucose metabolism."
Research Report:Reconstruction of the human amylase locus reveals ancient duplications seeding modern-day variation
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