From Fire to Farming: Uncovering Early Humans' Evolutionary Advantage in Starch Digestion

DNA from mouth bacteria suggests human ancestors ate diets rich in starchy plants by 600,000 years ago.Photo byMauricio Anton/Science Source

Two recent studies have shed light on how our early human ancestors evolved to digest starch better. They reveal that they possessed a surprising variety of amylase genes, which produce the enzyme that breaks down starch. This adaptation occurred in two significant waves: one several hundred thousand years ago, likely linked to the use of fire for cooking, and another around 12,000 years ago, coinciding with the agricultural revolution, two of humankind's most major milestones. 

Omer Gokcumen, a geneticist at the University at Buffalo, led one study that suggests as ancient societies diversified their diets, their genetic makeup reflected this change, with some individuals developing more amylase genes. This evolution may contribute to modern health issues, such as diabetes, in those with fewer amylase genes, highlighting the potential for future amylase-based treatments.

The research built on discoveries from the 1960s that noted individual amylase production variations. With advancements in DNA sequencing, scientists could now catalog the diversity of amylase genes in human DNA. While many people carry multiple copies of the amylase gene, apes like chimpanzees have only one.

Early humans may have evolved to have extra genes for breaking down starch after they started cooking tubers for food.Photo byJavier Trueba/MSF/Science Source

Fossil evidence reveals that early hunter-gatherers had around five copies of the amylase gene, and Neanderthals had similar traits. The research suggests that learning to control fire was vital for early humans because it allowed them to digest starchy plants better, significantly improving their diets.

The studies also show that natural selection favored people with more amylase gene copies, particularly after the last ice age when farming started. This increase in amylase genes was more common among groups that grew starch-rich crops, highlighting the connection between changes in diet and genetic evolution.