Starch-digesting gene likely evolved much before farming did, study finds

New Delhi: Genes that help humans digest carbohydrates could have started evolving more than 800,000 years ago, long before the advent of farming, a new study has found.

Analysing the genomes of 68 ancient humans, including a 45,000-year-old sample from Siberia, researchers at the University at Buffalo, US, found that pre-agricultural hunter-gatherers already had about four to eight copies of the amylase, or ‘AMY1’, gene — known to help break down starchy foods such as bread and pasta.

Gene duplication, whereby a gene copies itself and grows in number, is considered a major driver of evolution.

The results showed that the early duplication of the gene helped human adapt to starchy foods and set the stage for the wide genetic variation that still exists today, influencing how humans digest starchy foods effectively, the team said.

“The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest effectively,” Omer Gokcumen, a professor in the department of biological sciences, University of Buffalo, and corresponding author of the study published in the journal Science, said.

The initial copies of the amylase gene was like “the first ripple in a pond, creating a genetic opportunity that later shaped our species”, the researchers explained.

As humans spread across different environments, the gene’s copies provided an advantage for adapting to new diets, particularly those rich in starch, they said.

The team also found that the amylase gene duplications occurred in Neanderthals and Denisovans — both close and extinct relatives of the modern humankind.

“This suggests that the (amylase) gene may have first duplicated more than 800,000 years ago, well before humans split from Neanderthals and much further back than previously thought,” lead author Kwondo Kim, The Jackson Laboratory for Genomic Medicine, US, said.

“The initial duplications in our genomes laid the groundwork for significant variation in the amylase region, allowing humans to adapt to shifting diets as starch consumption rose dramatically with the advent of new technologies and lifestyles,” Gokcumen said.

The study also showed how agriculture affected evolution of the amylase genes.

While early hunter-gatherers had multiple gene copies, European farmers saw a surge in the amylase gene copies over the past 4,000 years, likely due to their starch-rich diets, the researchers said.

Those having more copies of the amylase gene were likely digesting starch more efficiently and having more offspring, Gokcumen said.

“Their lineages ultimately fared better over a long evolutionary timeframe than those with lower numbers, propagating the number of the (gene’s) copies,” Gokcumen said.