Spitting out clues to 'ghost species' of ancient human

Ancient Africans may have engaged in a 'sexual rendezvous' with a 'ghost' species of archaic humans, according to a recent study.

In saliva, University at Buffalo scientists found hints that a "ghost" species of archaic humans may have contributed genetic material to ancestors of people living in Sub-Saharan Africa today.

The research added to a growing body of evidence suggesting that sexual rendezvous between different archaic human species may not have been unusual.

The new research is among more recent genetic analyses indicating that ancient Africans also had trysts with other early hominins.

"It seems that interbreeding between different early hominin species is not the exception - it's the norm," said lead researcher Omer Gokcumen.

"Our research traced the evolution of an important mucin protein called MUC7 that is found in saliva," he noted. "When we looked at the history of the gene that codes for the protein, we see the signature of archaic admixture in modern day Sub-Saharan African populations."

The scientists came upon their findings while researching the purpose and origins of the MUC7 protein, which helps give spit its slimy consistency and binds to microbes, potentially helping to rid the body of disease-causing bacteria.

The study concluded that MUC7 appears to influence the makeup of the oral microbiome, the collection of bacteria within the mouth. The evidence for this came from an analysis of biological samples from 130 people, which found that different versions of the MUC7 gene were strongly associated with different oral microbiome compositions.

"From what we know of MUC7, it makes sense that people with different versions of the MUC7 gene could have different oral microbiomes," lead researcher Stefan Ruhl said. "The MUC7 protein is thought to enhance the ability of saliva to bind to microbes, an important task that may help prevent disease by clearing unwanted bacteria or other pathogens from the mouth."

The research is published in the journal Molecular Biology and Evolution.