Why Humans Digest Starch: The Historical Evolution of the Human Diet and the Genetics of Amylase Over More Than 800,000 Years

Our love for carbohydrates may be the result of a genetic adaptation that began more than 800,000 years ago, long before our ancestors developed agriculture. New research reveals that early humans, including Neanderthals, possessed multiple copies of the amylase (AMY1) gene, which plays a crucial role in breaking down starchy foods. This gene enables the breakdown of complex carbohydrates such as bread, potatoes, and grains as early as the oral cavity, ensuring rapid absorption of energy. This adaptation evolved as a response to dietary changes and is now considered one of the key factors that allowed humans to adapt to various diets around the world.

Analysis of ancient DNA from samples up to 45,000 years old, including those from Siberia, has shown that pre-agricultural hunter-gatherers had an average of four to eight copies of the AMY1 gene. This indicates that a wide variability of the amylase gene was present long before humans began cultivating plants and consuming larger quantities of starch. Interestingly, both Neanderthals and Denisovans also had more copies of this gene, suggesting that evolutionary changes occurred before modern human species diverged from these ancient relatives. This discovery sheds new light on the dietary habits of our ancestors, as well as the evolutionary pressures that shaped human metabolism.

As humans migrated from Africa to different parts of the world, genetic variations of the amylase gene allowed them to adapt to different food sources. In warmer regions, where plants were available year-round, the number of AMY1 gene copies helped people digest starchy foods more efficiently. In colder regions, where plant-based food was more limited, these genetic adaptations may not have been as significant. However, during the transition from hunter-gatherer societies to agricultural societies, there was an increase in starch consumption, and thus an increase in the number of gene copies.

Agriculture brought key changes to human diets. Due to the spread of starchy crops like wheat, corn, and rice, the number of AMY1 gene copies increased over the past several thousand years. Research has shown that Europeans have increased their average number of gene copies from four to seven over the last 12,000 years. This rise in gene copies allowed for more efficient digestion of starch-rich foods, ensuring better access to energy and helping humans survive in times of food scarcity.

Neanderthals and Denisovans also had more copies of the amylase gene, indicating that they too consumed significant amounts of starchy food. Genome analysis of these ancient humans revealed that AMY1 gene copies existed even before the divergence between modern humans and Neanderthals, meaning that this genetic adaptation is older than previously thought. This discovery further underscores the importance of amylase in human evolution and adaptation to a carbohydrate-rich diet.

The amylase gene not only plays a role in starch breakdown but also affects the taste of bread and other baked goods. Amylase, an enzyme produced in saliva, breaks down starch into simple sugars, enhancing flavor and speeding up digestion. This ability was crucial in human evolution, allowing our ancestors to extract more energy from available resources and survive in environments with limited food. Agricultural communities, particularly in Europe, showed a significant increase in the number of amylase gene copies, enabling better digestion of starchy foods that made up a large part of their diet.

Today’s research continues to uncover the complexity of genetic adaptations related to amylase. Scientists are studying the relationship between the number of copies of this gene and various metabolic conditions, such as obesity and diabetes. These studies could open new possibilities for understanding human metabolism and help develop targeted therapies for diseases related to carbohydrate-rich diets. Genetic variations associated with amylase also provide insight into the evolutionary changes that have shaped human populations around the world, highlighting the significance of this enzymatic adaptation in human history.

These discoveries provide important information about how human diets have evolved over time and how genetic changes have played a crucial role in our adaptation to different environments. Evidence suggests that the ability to digest starch gave our ancestors a significant evolutionary advantage, allowing them better nutrition and energy in times when resources were scarce. Scientists continue to explore genetic variations associated with amylase to better understand its role in modern human health and evolution.

Source: University at Buffalo