Ancient DNA suggests our love for carbs goes back 800,000+ years

BUFFALO, N.Y. — Our craving for bread, pasta, and potatoes may be more than just a cultural preference – it could be encoded in our DNA. Research reveals that our ability to digest starchy foods has much deeper roots than previously thought, potentially explaining why so many of us find carbohydrates irresistible.

Published in Science, this eye-opening research delves into the evolutionary history of a gene called AMY1, which produces salivary amylase – the enzyme that starts breaking down starches as soon as they hit our mouths. For years, scientists have known that humans carry multiple copies of this gene but pinpointing when and how these copies multiplied has been as tricky as resisting a warm, crusty baguette.

“The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest effectively,” says the study’s corresponding author, Omer Gokcumen, PhD, a professor in the Department of Biological Sciences at the University at Buffalo, in a media release.

A team of researchers from the University at Buffalo and the Jackson Laboratory decided to take a fresh bite out of this mystery. Armed with cutting-edge genomic tools like optical genome mapping and long-read sequencing, they set out to map the AMY1 gene region in a level of detail that would make a master chef proud.

The genetic feast they uncovered was more varied and complex than anyone had imagined. Among the 98 individuals studied from around the world, the team identified 52 distinct amylase haplotypes – think of these as different recipes for the AMY1 gene. Thirty of these stood out as particularly well-supported findings, suggesting that this gene region has been simmering with change throughout human history.

But the real showstopper came when the researchers peered into our evolutionary past. By examining ancient DNA from Neanderthals, Denisovans, and early modern humans, they found evidence of AMY1 gene duplications that push back the origin of our starch-digesting prowess to over 800,000 years ago. That’s long before our ancestors even dreamed of agriculture!

“This suggests that the AMY1 gene may have first duplicated more than 800,000 years ago, well before humans split from Neanderthals and much further back than previously thought,” says Kwondo Kim, one of the lead authors on this study from the Lee Lab at JAX.

This ancient genetic prep work didn’t go to waste. When the team analyzed 68 ancient human genomes, including one from a 45,000-year-old individual found in Siberia, they discovered that even these ancient hunter-gatherers were carrying multiple copies of the AMY1 gene. It seems our ancestors were genetically equipped for a carb-heavy diet long before they started cultivating grains.

The plot thickens like a rich risotto when we look at more recent history. Over the last 4,000 years, European farmers experienced a surge in high-copy AMY1 haplotypes. As agriculture spread, so did genetic variations allowing for even more efficient starch processing. It’s as if our genes and our growing appetite for grains were evolving in perfect harmony.

“Individuals with higher AMY1 copy numbers were likely digesting starch more efficiently and having more offspring,” Gokcumen explains. “Their lineages ultimately fared better over a long evolutionary timeframe than those with lower copy numbers, propagating the number of the AMY1 copies.”

So how did all this genetic diversification happen? The researchers identified several mechanisms, but one stands out: non-allelic homologous recombination, or NAHR. Think of it as nature’s way of accidentally duplicating recipe cards – sometimes you end up with extra copies, sometimes fewer. This genetic lottery explains why some of us hit the jackpot with extra AMY1 copies, potentially making us carb-digesting champions.

Interestingly, while the number of AMY1 copies can vary widely between individuals, the actual protein-coding sequences remain remarkably stable. It’s as if evolution is saying, “Feel free to make more copies of this recipe, but don’t change the ingredients!”

This research isn’t just food for thought about our past – it has real implications for our present and future health. Understanding how our genes have adapted to dietary changes could shed light on modern issues related to starch consumption and digestion. It might even explain why some of us find it harder to resist that second helping of mashed potatoes.

“Given the key role of AMY1 copy number variation in human evolution, this genetic variation presents an exciting opportunity to explore its impact on metabolic health and uncover the mechanisms involved in starch digestion and glucose metabolism,” says Feyza Yilmaz, an associate computational scientist at JAX and a lead author of the study. “Future research could reveal its precise effects and timing of selection, providing critical insights into genetics, nutrition, and health.”

Indeed, our genetic past continues to influence our present in ways we are only beginning to understand. As Yilmaz suggests, similar studies promise not only to shed light on human evolution but also to provide crucial insights that could help address modern health challenges related to diet and metabolism.