Utilizing an algorithm that analyzes genomes, a group of scientists looked at the interbreeding of ancient humans with other species. They found that species belonging to different branches of our family tree interbred on many occasions. The scientists also found DNAOpens in a new tab from a mysterious ancestor, which is still present in some living people’s genomes.
#NewResearchOpens in a new tab Hubisz et al present ARGweaver-D, an extension of the ARGweaver algorithm, and predict that 1% of the #DenisovanOpens in a new tab genome was introgressed from an unsequenced, but highly diverged, archaic hominin ancestor: https://t.co/6FO8xHjlQfOpens in a new tab pic.twitter.com/c4tDOEG0IgOpens in a new tab
— PLOS Genetics (@PLOSGenetics) August 11, 2020Opens in a new tab
ZME ScienceOpens in a new tab reported on the discovery, which was made by Melissa Hubisz and Amy Williams of Cornell University, and Adam Siepel of Cold Spring Harbor Laboratory. The team recently published its research in PLOS GeneticsOpens in a new tab. In their paper, the scientists describe Hubisz’ “ancestral recombination graph” algorithm, dubbed ARGweaver-D. Using ARGweaver-D, Hubisz et al. were able to identify segments in Homo sapien DNA that come from other speciesOpens in a new tab. Even if that so-called “gene flow” took place thousands of years ago and occurred due to an unknown source.
Our latest — encompassing the last of the dissertation work of the great Melissa Hubisz: Mapping gene flow between ancient hominins through demography-aware inference of the ancestral recombination graph https://t.co/9wUDQksJZDOpens in a new tab
— Adam Siepel (@asiepel) August 8, 2020Opens in a new tab
Using ARGweaver-D, the scientists found that the DenisovansOpens in a new tab, a subspecies of archaic human—which may, in fact, be its own distinct species—have a genome that contains one percent of DNA from an unknown and more distant relative. And because the Denisovans interbred with ancestors of H. sapien, they passed on some of that mysterious relative’s genes. By the accounts of ARGweaver-D, about 15% of these “super-archaic” genetic sequences may be present in some modern humans.
“This new algorithm that Melissa has developed, ARGweaver-D, is able to reach back further in time than any other computational method I’ve seen,” Siepel told Science DailyOpens in a new tab. The computational biologist added that the algorithm is especially good at detecting ancient introgression. Introgression is the movement of genes from one species into the pool of another by way of an intermediary hybrid.
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Although the scientists are uncertain of who the mysterious relative is, some speculate that it could be Homo erectusOpens in a new tab. H. erectus, or “upright man,” lived between approximately 1.9 million and 110,000 years ago. The picture above shows a reconstruction of a potential subspecies of H. erectus, Homo erectus georgicus.
Along with the mysterious DNA, scientists also confirmed previously reported cases of gene flow between ancient humans and their relatives. In fact, there’s apparently enough evidence at this point to think that, as Science Daily notes, “genetic exchange was likely whenever two groups overlapped in time and space.”
John D. CroftOpens in a new tab
In the future, researchers will use ARGweaver-D to identify more evidence of gene flow between H. sapien and other species. The algorithm will also be useful for identifying instances of interbreeding among other species, such as in wolves and dogs.
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