Hominin Interbreeding More Extensive than Previously Thought

New study reveals mysterious DNA in archaic human genome.

Michael Capitano, Staff Writer

While it is generally accepted within the scientific community that the ancestors of modern Homo sapiens regionally interbred with other hominins, Neanderthals and Denisovans, before their eventual extinctions, a genome analysis reveals that an enigmatic human species was also in the mix.

These recent findings, published in Nature and presented on November 18 at the Royal Society in London, show that the genome of a now extinct hominin species, the Denisovans, also contained DNA from another human group. All modern humans, whose ancestors originated outside of Africa, share a minimal amount of DNA with other human species. What the recent analysis reveals, however, is that an additional species of hominin, different than those of anatomically modern humans, Neanderthals and Denisovans, intermingled with the Denisovan populations that lived in Asia some 30,000 years ago.

Although the identity of this human group remains unknown, the findings have created a buzz in the scientific community, with many scientists offering theories on the identity of the mystery DNA.

Chris Stringer, a paleoanthropologist at the Natural History Museum in London, suggests that the new human species could be related to the hominin group Homo heidelbergensis¸ making this the first genetic record of previously discovered hominins known only from their fossilized remains.

Either way, the findings, suggest that human interbreeding was more extensive than previously thought. According to David Reich, an evolutionary geneticist at Harvard Medical School, the prior conclusions on early human movement and interaction were based on low-quality genome sequences, riddled with gaps and errors. The more complete versions of these genomes used in the study, extracted from bones found in Denisova Cave in Siberia, match the quality of contemporary human genomes.

The lineages of Neaderthals and Denisovans branched off from modern humans approximately 400,000 years ago, before separating into their respective species. Although they are genetic cousins, according to Reich, “Denisovans appear more distinct from modern humans than Neanderthals… [and] harbour ancestry from an unknown archaic population, unrelated to Neanderthals.”

The new genome sequences were discussed extensively at the Royal Society in London, drawing comparisons to popular fantasy narratives where different human species interact with one another.

“What it begins to suggest is that we’re looking at a ‘Lord of the Rings’-type world — that there were many hominid populations,” says Mark Thomas, attendee at the meeting and evolutionary geneticist at University College London.

Whatever the truth may be, the new genome sequences add to the ever-growing and complex picture of human evolution and encourages speculation about how and why modern humans, and not our archaic relatives, exist in present day.

Michael Capitano is a second year law student at Osgoode Hall Law School. He is an aspiring novelist and essayist. He enjoys spending most of his time reading, writing, and playing video games.

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Image Courtesy of Stew Dean.