In saliva, scientists have found hints that a “ghost” species of archaic human may have contributed genetic material to ancestors of people living in Sub-Saharan Africa today.
Image credit: Bob Wilder/University at Buffalo.
As an example of how divorced religion is from reality, these examples of archaic hominids interbreeding with other hominid species take some beating.
The Abrahamic superstitions require people to believe in a single founder couple from whom everyone alive is directly descended and from whom we have inherited some notional 'original sin' for which we need to constantly atone and beg for forgiveness.
The reality of course is that not only was there never such a single founder human couple but there was not even a single founder human species. The reality is that we are hybrids of three or more species who occasionally interchanged genes and that for a large part of our recent evolutionary history we behaved like an incompletely speciated 'ring species' as an example of evolution in progress.
There is now little doubt that modern non-African peoples have some Neanderthal DNA and many have some Denisovan DNA, possibly some Homo erectus DNA and some DNA from an as yet unidentified species, not inherited by virtue of common ancestry but by introgression, i.e., gene flow between co-existing populations. Now this paper by a team of researchers from the USA and Greece shows that the African hominid ancestors of modern humans may also have interbred with other hominid species.
The open access paper was published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Abstract
One of the most abundant proteins in human saliva, mucin-7, is encoded by the MUC7 gene, which harbors copy number variable subexonic repeats (PTS-repeats) that affect the size and glycosylation potential of this protein. We recently documented the adaptive evolution of MUC7 subexonic copy number variation among primates. Yet, the evolution of MUC7 genetic variation in humans remained unexplored. Here, we found that PTS-repeat copy number variation has evolved recurrently in the human lineage, thereby generating multiple haplotypic backgrounds carrying 5 or 6 PTS-repeat copy number alleles. Contrary to previous studies, we found no associations between the copy number of PTS-repeat copy number and protection against asthma. Instead, we revealed a significant association of MUC7 haplotypic variation with the composition of the oral microbiome. Furthermore, based on in-depth simulations, we conclude that a divergent MUC7 haplotype likely originated in an unknown African hominin population and introgressed into ancestors of modern Africans.
Duo Xu, Pavlos Pavlidis, Recep Ozgur Taskent, Nikolaos Alachiotis, Colin Flanagan, Michael DeGiorgio, Ran Blekhman, Stefan Ruhl, Omer Gokcumen
Archaic hominin introgression in Africa contributes to functional salivary MUC7 genetic variation
Mol Biol Evol msx206. DOI: 10.1093/molbev/msx206
© The Author(s) 2017.
Published by Oxford University Press on behalf of the Society for Molecular Biology and Evolution.
Reprinted under the terms of a Creative Commons Attribution 4.0 Non-Commercial License (CC BY-NC 4.0)
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. 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.
Omer Gokcumen, co-author
Assistant professor
Department of Biological Sciences
Assistant professor
Department of Biological Sciences
From the known rates of gene mutation the team calculated that this strange MUC7 gene had diverged from that in the non-African people 1.5 to 2 million years ago and had then introgressed into the sub-Saharan genome some 150,000 years ago.
The gene for MUC7 occurs in two forms; one with six copies of the coded instruction for parts of the protein and one with only five copies (I wonder what creationists would make of that!). Although the purpose of MUC7 remains unknown, the team also found a strong correlation between the different gene variants and the composition of the oral microbiome, so it appears to influence the types of microorganisms that can live in the mouth.
Just another example of the facts revealed by biological science refuting creationism without even trying.
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