Clues To Our “Ghost” Ancient Ancestors Found In Saliva

What’s in saliva?

Every now and then, science tends to uncover something that’s outright weird and leaves us flabbergasted.

Guess you now know where am going, with an opening like that.

Now, once again, genomic analysis has revealed the evidence of the archaic human within.
Previous studies have concluded that our forefathers in Asia and Europe interbred with other early hominin species, including Neanderthals and Denisovans. Now, a new research has revealed that ancient Africans also had trysts with other early hominins. The evidence of this “ghost” species of hominin that they had carnal trysts with, is making its presence known through a salivary protein—or rather, a gene that codes for an unusual version of this protein, which is known as MUC7.

As if saying I have my mother’s eyes was not enough, you could now also say I have my great-great-great….great-grandmother’s saliva.

A variation on this MUC7 gene for our spit’s mucus shows signs of having been passed down from a distant ancestor. Not only is this gene unique among modern humans, it looks nothing like the one possessed by our Neanderthal or Denisovan cousins; thereby prompting the scientists to investigate.

MUC7 is a gene that makes the long strings

of protein called mucin, which gives our spit its thick, sticky quality. Not all MUC7 genes are alike, with a repeating region of code marking out variations that could be useful in tracing back different lineages in our modern human population.

This exactly was the plan for a team of researchers from the University of Buffalo, who analyzed the mucin-7 gene from more than 2,500 individual genomes from modern humans to see what secrets these differences might hold.

“Based on our analysis, the most plausible explanation for this extreme variation is archaic introgression – the introduction of genetic material from a ‘ghost’ species of ancient hominins,” explains Omer Gokcumen, study author from the University at Buffalo College of Arts and Sciences, in a statement. “This unknown human relative could be a species that has been discovered, such as a subspecies of Homo erectus, or an undiscovered hominin. We call it a ‘ghost’ species because we don’t have the fossils.”

Given the rate at which genes mutated during the course of evolution, the team calculated that the ancestors of people who carry the Sub-Saharan MUC7 variant interbred with another ancient human species as recently as 150,000 years ago, after the two species’ evolutionary path diverged from each other some 1.5 to 2 million years ago.

To put it into some perspective, we probably parted ways with the ancestors of the Neanderthals about 400,000 years ago, though still stayed in touch over the millennia. Which going by the MUC7 discovery, is not all that uncommon.

“It seems that interbreeding between different early hominin species is not the exception – it’s the norm,” says Gokcumen.

This discovery definitely adds further complexity to the pathway of human evolution. It seems the modern Homo sapiens may have evolved from a variety of different ancient species, including several mysterious variants we have yet to fully uncover.