Long before people ate sandwiches or French fries, our ancestors carried genes that would later help us digest starchy foods.
Amylase genes produce an enzyme in saliva and the intestines that is essential for breaking down starch into sugar. That’s why pasta, if you eat it long enough, starts to taste sweet. Digesting starch, a type of carbohydrate, is a crucial part of how we get energy from food.
New research published Thursday in the journal Science suggests that the amylase gene has a much longer evolutionary history than scientists previously thought.
The study found evidence that our human ancestors began carrying multiple copies of the gene as early as 800,000 years ago.
“That not only predates agriculture, but also predates the migration of humans out of Africa,” said Omer Gokcumen, a co-author of the study and a professor of biological sciences at the University at Buffalo.
The study also found evidence of multiple amylase copies in Neanderthals and Denisovans, ancestral cousins of modern humans. Previously, it was only confirmed that the gene began duplicating with the advent of agriculture about 12,000 years ago.
It’s not clear what the purpose of the amylase gene was when those ancient ancestors lived, Gokcumen said, though it’s possible that Neanderthals included starch in their largely carnivorous diet.
Today, he added, amylase could partly explain why starchy foods taste good to us. Some studies have suggested that populations with higher amylase copies tend to eat more starch, though more research is needed to test those theories.
Peter Sudmant, an assistant professor of integrative biology at the University of California, Berkeley, who was not involved in the new study, published his own research on the amylase gene last month. That study, in the journal Nature, suggested that humans acquired more copies of amylase genes with the advent of agriculture in Europe 12,000 years ago, and as a result became better adapted to starchy diets.
“When people started eating a lot more starch, there was probably a survival advantage for people with more amylase genes,” Sudmant said.
As for the role of amylase genes today, scientists are still figuring out whether having a large number of the genes is beneficial to people or poses a risk of negative health consequences. (Sudmant noted that studies have linked the presence of more amylase copies to cavities, since the enzyme converts starchy foods into sugar.)
Before agriculture developed, he said, it’s possible that the gene existed for no reason at all.
“It could just be floating around and serving no purpose,” he said. “Not everything in our genome has a purpose. … There are things that just exist.”
Both recent studies relied on a relatively new technology to analyze genetic material from ancient humans. The tool, called long-read sequencing, allows scientists to read entire genomes, including regions that were previously difficult to observe in detail. In this case, it gave them an unprecedented look at the region that contains amylase genes.
Gokcumen’s study analyzed genetic material from 68 ancient people, including a sample of 45,000-year-old remains from Siberia and a 34,000-year-old sample from Romania. Sudmant’s study, meanwhile, looked at hundreds of ancient genomes.
“We could look at dozens of individuals from diverse ancestral backgrounds in a comprehensive way,” Gokcumen said. “And once we do that, we can essentially start to reconstruct evolutionary history.”