If you've ever found it hard to resist that extra slice of bread or bowl of pasta, the explanation might lie deep within your DNA. A groundbreaking study, co-led by the University at Buffalo (UB) and the Jackson Laboratory (JAX), suggests that our love for carbohydrates may have roots that stretch back hundreds of thousands of years, well before the advent of agriculture.
The Gene Behind Our Carb Cravings
For many years, scientists have known that humans possess multiple copies of the salivary amylase gene (AMY1), which helps us digest starchy foods. However, the exact timeline for the gene's duplication and its role in human evolution remained unclear—until now.
A new study published in Science reveals that this gene's expansion may have started more than 800,000 years ago. This timeline suggests that the ability to digest starch-rich foods predates both agriculture and our evolutionary split from Neanderthals. This early adaptation likely played a crucial role in shaping our ancestors' diets and survival strategies.
Unlocking the Secrets of the AMY1 Gene
AMY1 is responsible for producing amylase, an enzyme found in saliva that begins breaking down starches as soon as they enter our mouths. This process is key to our ability to metabolize foods like bread, rice, and potatoes. The more copies of AMY1 a person has, the more efficiently they can digest these starchy foods.
Using advanced genome mapping techniques, researchers were able to trace the evolution of the AMY1 gene, providing a clearer picture of how this gene duplicated and spread. Previous methods struggled to differentiate between nearly identical gene copies, but with long-read sequencing, the research team overcame this hurdle.
Omer Gokcumen, PhD, a professor of biological sciences at UB, explains: "The idea is that the more amylase genes you have, the more amylase you can produce, and the more starch you can digest effectively."
Ancient Diets and Genetic Adaptations
One of the most fascinating discoveries in this study is that even before humans began farming, ancient hunter-gatherers had multiple copies of the AMY1 gene. This genetic advantage would have allowed them to thrive in environments where starch-rich plants were part of the diet.
The research team analyzed genomes from 68 ancient humans, including a 45,000-year-old sample from Siberia. These early humans had an average of four to eight copies of the AMY1 gene. Not only did our ancestors possess these extra gene copies, but so did Neanderthals and Denisovans, our distant relatives.
"This suggests that the AMY1 gene may have first duplicated more than 800,000 years ago," notes Kwondo Kim, one of the lead authors of the study. This timeline places the gene's duplication well before humans split from Neanderthals, providing new insights into our shared evolutionary history.
Farming's Impact on AMY1 Gene Variation
While ancient hunter-gatherers already carried multiple AMY1 gene copies, the rise of agriculture further shaped its variation. Farming communities, particularly in Europe, experienced a surge in AMY1 copies over the past 4,000 years as they began to consume more starch-heavy diets.
"Individuals with higher AMY1 copy numbers were likely digesting starch more efficiently, allowing them to have more offspring," says Gokcumen. This evolutionary advantage meant that their lineages were more likely to survive and pass on the gene, resulting in a higher prevalence of AMY1 copies in modern humans.
Interestingly, domesticated animals like dogs and pigs—who lived alongside humans—also developed higher AMY1 gene copy numbers, showing the broader impact of agricultural diets on different species.
The Genetic Foundation for Modern Diets
The initial duplication of the AMY1 gene set the stage for significant genetic variation in human populations. As humans spread across different environments, their ability to digest starch gave them a nutritional edge.
Charikleia Karageorgiou, a lead author from UB, explains that the number of AMY1 copies varies widely: "From three AMY1 copies, you can get all the way up to nine copies, or even go back to one copy per haploid cell." This flexibility allowed humans to adapt to new diets as they encountered different environments and technologies.
A Look Into the Future: Nutrition and Health Implications
As the study sheds light on our genetic history, it also opens the door for future research into how AMY1 variation affects modern metabolic health. Feyza Yilmaz, an associate computational scientist at JAX, points out that understanding this gene could help us explore the relationship between genetics, starch digestion, and glucose metabolism.
"Future research could reveal its precise effects and timing of selection, providing critical insights into genetics, nutrition, and health," says Yilmaz. These findings could lead to new ways of understanding dietary needs, improving nutrition guidelines, and even developing personalized diets based on individual genetic profiles.
A Long History of Loving Carbs
In short, our love for carbs may not just be about flavor or comfort—it could be written in our DNA. The ancient duplication of the AMY1 gene laid the groundwork for humans to thrive on starchy diets, influencing our evolutionary path and even our modern relationship with food. As science continues to unlock the secrets of our genetic past, we may discover even more ways in which our distant ancestors shaped the world we live in today.
This study was a collaboration between UB, JAX, the University of Connecticut Health Center, and was supported by the National Science Foundation and the National Human Genome Research Institute.