Humans carry multiple copies of a gene that allows them to begin breaking down the starch of complex carbohydrates in the mouth, the first step in the metabolism of foods like bread and pasta. But when did this genetic expansion begin? A new study suggests it dates back more than 800,000 years.
Led by researchers from the University at Buffalo and the Jackson Laboratory for Genomic Medicine – both in the United States – this study shows how the first duplications of this gene laid the foundation for the wide genetic variation that still exists today and which influences the efficiency with which humans. digest starchy foods.
“If you’ve ever had trouble cutting down on your carb intake, ancient DNA could be to blame.“, summarizes a press release from the aforementioned laboratory.
The research findings are published in the journal Science and reveal that duplication of the aforementioned gene – known as the salivary amylase gene (AMY1) – may not only have helped shape human adaptation to starchy foods, but that it could have occurred well before the arrival of starchy foods. of agriculture.
“The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest efficiently.” explains Omer Gokcumen of the University at Buffalo. Amylase is an enzyme that not only breaks down starch into glucose, but also gives bread flavor.
To reach their conclusions, the team, also led by Charles Lee, used advanced genomic techniques to map the AMY1 gene region in extraordinary detail.
Genomes of 68 ancient humans
By analyzing the genomes of 68 ancient humans, including a 45,000-year-old sample from Siberia, he found that pre-agricultural hunter-gatherers already had an average of four to eight copies of AMY1 per diploid cell, suggesting that humans were already roaming Eurasia. with a wide variety of high AMY1 copy numbers long before they began domesticating plants and eating excessive amounts of starch.
The study also found that duplications of the AMY1 gene occurred in Neanderthals and Denisovans. “This suggests that the AMY1 gene may have first duplicated itself more than 800,000 years ago, long before humans separated from Neanderthals and much earlier than previously thought,” explains Kwondo Kim from the Jackson laboratory.
Gokcumen adds: “The initial duplications in our genomes laid the foundation for significant variation in the amylase region, which allowed humans to adapt to changes in their diet as starch consumption increased significantly with the advent of new technologies and lifestyles“.
The research also highlights the impact of agriculture on AMY1 variation. While early hunter-gatherers had multiple copies of the gene, European farmers have experienced an increase in average AMY1 copy numbers over the past 4,000 years, likely due to their starchy diets.
Additionally, Gokcumen’s previous research had shown that domestic animals that live with humans, such as dogs and pigs, also had higher AMY1 copy numbers than animals that are not dependent on a diet. rich in starch.
