New studies have provided immense clarity on the development of human saliva, pointing to its establishment from harkening primate past. Stefan Ruhl, DDS, Ph.D., and Omer Gokcumen, Ph.D., head a vibrant, multifaceted lab. Their investigation sheds new light on the complicated makeup of saliva and how it plays an important part in protecting human health. The results appeared in the journal Genome Biology and Evolution, DOI 10.1093/gbe/evaf165.
Saliva consists of over 3,000 different molecules, many of which are similar to those found in blood. Of these components, no more than a dozen or so exist in high abundance. This complex combination performs important functions in digestion, fortification of dental enamel, and protection against infectious diseases. The study indicates that protein-coding genes involved in human saliva production have undergone dramatic evolution over the years. They’ve continued to suffer duplications, lost and changed regulatory requirements.
This development shows just how well the evolution of this important secretion has been conserved, particularly within the lineage of the primates. Though human saliva is more than 98% genetically similar to that of apes, a lot has changed in its protein composition. Diet is one of the most important factors affecting saliva production. These differences underscore the influence dietary adaptations play in defining the functional uniqueness of human saliva as compared with our closest primate relatives.
The research team was especially proud to include on their work Petar Pajic, former Ph.D. student and first author on the paper. Fifth-year biological sciences Ph.D. student Luane Landau contributed significantly to the project. Together, their collaborative efforts illuminate the unique evolutionary history that has left its mark on human saliva.
These discoveries not only further the basic understanding of saliva’s importance to oral health, but underscore its evolutionary importance. To understand what makes the composition of saliva so complicated, researchers are starting. Along the way, they will likely discover new understandings of how biological systems adapt to changes over time.