“This observation is consistent with recent evidence of starch consumption by Neanderthals, and perhaps the availability of cooked starch in archaic hominins, made possible by the domestication of fire,” the researchers said in a study recently published in Science .
Of the eight genomes examined, multiple copies of AMY1 were found in two eastern Neanderthal genomes, one from a western Neanderthal and one from a Denisovan. So why did these extra copies evolve? Although the exact reason is still unknown, the team thinks that the gene itself was variable copy number, meaning that the number of copies within a population can vary from person to person. This variation probably evolved before humans diverged from Neanderthals and Denisovans.
With the grain
For the research team, it was inevitable that the number of copies of AMY1 in individual genomes would increase as former hunter-gatherers established agricultural societies. Agriculture meant grains and other starchy foods, and the ability to modify them meant carbohydrates.
And the data here is consistent with that. The team “found a general trend whereby the number of AMY1 gene copies is significantly higher among samples excavated from archaeological agricultural contexts compared to those from hunter-gatherer contexts,” they said in the same study.
In genomes of pre-agricultural individuals, four to eight copies of the gene were already present. The variation is believed to come from groups experimenting with food processing techniques, such as grinding wild grains into flour. The number of AMY1 copies grew quite consistently from the pre-agricultural to the post-agricultural period. Individuals from populations that were in the process of transitioning to agriculture (about 16,100 to 8,500 years ago) were found to have approximately similar AMY1 copy numbers as hunter-gatherers at the time.
Individuals after 8,500 years ago who lived in more settled agricultural societies showed the most copies and therefore the most evidence of adaptation to eating high-carbohydrate diets. Agriculture continued to advance and the last 4000 years saw the largest increase in AMY1 copies. Modern humans have between two and fifteen copies.
Further research could help understand how genetic variation of AMY1 copy numbers affects starch metabolism, including conditions such as gluten allergy and celiac disease, and overall metabolic health.
Can we really blame AMY1 and amylase for our carb cravings? Partially. The number of AMY1 copies in a human genome not only determines its ability to metabolize starch, but will also influence its taste, and may have given us a preference for it. Maybe we can finally ease up on demonizing bread.
Science, 2024. DOI: 10.1126/science.adn060
