Human ancestors living in Sub-Sahara Africa may have
interbred with unknown “ghost’’ species of early hominins, a study on the
evolutionary history of a salivary protein has indicated.
“This unknown human relative could be a species that has
been discovered such as a subspecies of Homo erectus, or an undiscovered
hominin,’’ Omer Gokcumen, assistant professor at the State University of New
York at Buffalo, said in a recent statement.
“We call it a “ghost’’ species because we don’t have the
fossils,’’ he added.
The new research is among the most recent genetic analyses
indicating that ancient Africans also had trysts with other early hominins.
The research team traced the evolution of an important mucin
protein called MUC7 that was found in human saliva, examining its gene in more
than 2,500 modern human genomes.
“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,’’ Gokcumen said.
The research team found that a group of genomes from
sub-Saharan African populations had a version of the gene that was wildly
different from versions found in other modern humans, even beyond the
differences between modern humans and the Neanderthals or Denisovans.
The finding, published on Britain’s Molecular Biology and
Evolution journal, showed that the ancestry of Homo sapiens are more
complicated than originally believed.
Study showed that genes mutate during the course of
evolution.
Thereby researchers calculated that the ancestors carrying
Sub-Saharan MUC7 variant interbred with the “ghost’’ hominin species as recent
as 150,000 years ago, after the two species’ evolutionary path diverged from
each other some 1.5 to 2 million years ago.
The new studies also found that the MUC7 gene helps give
spit its slimy consistency and binds to microbes, potentially helping to rid
the body of disease-causing bacteria.
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