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New research shows saliva could be key to understanding human evolution

By Dental Tribune International
October 22, 2019

BUFFALO, N.Y., U.S.: Much is already known about saliva’s benefits for food digestion and general oral health. The differences between human saliva and that of other primates, however, are relatively unclear. A new study has discovered stark differences between human and primate saliva, leading to hope that these could be “overlooked hotbeds of evolutionary activity,” according to one of the study’s authors.

In the study, researchers from the University at Buffalo compared the proteins in human saliva with those in the saliva of other primates. To their surprise, they found that human saliva is much more watery than and contains half as many total proteins as the saliva of great apes and Old World monkeys does. These differences are, reportedly, a development of the human diet and its focus on increased meat consumption, cooking and agriculture.

Though all of the major proteins in human saliva were also present in chimpanzee and gorilla saliva, vast differences were noted in protein structure and quantity. Human saliva was found to possess higher amounts of amylase, an enzyme that is key to digesting starch into sugars, and carbonic anhydrase VI, an enzyme involved in taste perception.

“We know too little about the functions of saliva and the protein components in there. The findings of this study underscored that,” Prof. Stefan Ruhl, Acting Chair of the Department of Oral Biology at the University at Buffalo’s School of Dental Medicine and co-author of the study, told Dental Tribune International.

“Great apes eat a completely different diet than we humans do. Humans eat a lot of meat and starch-containing food. This goes back to our ancestors, who learned to hunt and discovered the procedure of cooking meat to make it more tender. The consumption of starch, on the other hand, has increased a lot since humankind invented agriculture. Those human-specific developments, we believe, have left their footprints in the composition and structure of proteins in human saliva, which we call the salivary proteome,” Ruhl continued.

“Once we know better about how the structure of certain salivary proteins dictates their function in health and disease, we will be able to use saliva-based diagnosis for predicting the susceptibility of certain individuals to dental caries or periodontal disease. We will also be able to come closer to synthesizing artificial saliva that will help patients who suffer from dry mouth,” he added.

The study, titled “Human and non-human primate lineage-specific footprints in the salivary proteome,” was published online on Oct. 15, 2019, in Molecular Biology and Evolution, ahead of inclusion in an issue.

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