Evolutionary Insight: Tracing the Genetic Story of Human Saliva Back to Primates
A team of researchers from the University at Buffalo (UB) embarked on a fascinating journey to answer a simple question: what can saliva tell us about human evolution? Their curiosity led to a profound discovery: the protein genes responsible for human saliva have been repeatedly duplicated, lost, and "re-tuned" over time—changes that stand out dramatically along the primate lineage and continue to influence our oral disease risk today.
The research provides a compelling look into how this vital biological fluid, which constantly interacts with food, microbes, and pathogens, has evolved more rapidly than many other bodily systems.
The Surprising Differences from Apes
Initially, researchers assumed that human saliva would closely mirror that of apes, given the over 98% genetic homology between the species. However, they were surprised by the differences they found in the composition of salivary proteins.
Rapid Evolution: Unlike blood composition, which is nearly identical, the genes for saliva proteins showed extensive diversification. The team concluded that the genetic locus controlling these proteins is "highly malleable to evolutionary innovation."
The Driver: Diet: Diet emerged as a major evolutionary force. For example, non-human primates have relatively low amounts of salivary amylase (the enzyme that breaks down starch). Humans, in contrast, have significantly more, a change that reflects early human adaptation to a starch-rich diet.
The Role of Saliva in Oral Defense
The research highlights the complex protective role of saliva proteins, which are critical because teeth are the only mineralized substance in the body constantly exposed to the environment, enduring challenges from dietary acids, bacterial by-products, and chewing.
Salivary proteins are crucial for:
Oral Health: Keeping the mouth healthy, especially considering that saliva contains almost every substance found in blood.
Mineralization: Providing the calcium necessary for bone growth in infants and protecting teeth throughout life through remineralization.
Immunity: The diversity of saliva proteins in primates is thought to aid in distinguishing between different taste varieties and protecting against harmful substances in the plants they consume.
By positioning saliva-related genes as key points for evolutionary adaptation influenced by dietary and pathogenic pressures, the study opens the door to better understanding individual differences in oral disease risk and potentially developing personalized oral health diagnostics.
Original Article Details
Original Title: Curiosity about saliva led UB team to trace its evolutionary story back to primates
Source: Oral Health Group
Publication Date: November 7, 2025