Tikalon Blog by Dev Gualtieri

Curse of the Neanderthal DNA

March 7, 2016

Neanderthal Man was a record by the English band, Hotlegs. It was released on June 19, 1970, at about the time of my exit from commercial radio broadcasting. Neanderthal Man was a reduction of rock-and-roll music into its basic elements, so it was like the musical analog of the abstract art movement.[1] It had a repetitive drum beat, and a nearly inaudible lyric reminiscent of another song, Louie Louie. The record was popular, selling two million copies.

Neanderthal Man by Hotlegs, cover for seven-inch single.

The seven-inch, 45 RPM, vinyl record format had the advantage that all the audio was concentrated at the periphery, so the linear density of the mechanical audio was fairly constant along the spiral track.

(Still image from a YouTube video.)

It's easy to see how this record was named. The overarching drum beat evokes the image of primitive men dancing around a campfire; or, at least, our popular conception of what primitive men would do around a campfire. The human subspecies, Homo sapiens neanderthalensis, the Neanderthal Man, which became extinct around 40,000 years ago, was not that different from modern man. DNA analysis has shown that Neanderthal and human genomes are at least 99.5% identical.[2]

Facial reconstraction of a male Homo sapiens neanderthalensis by Cicero Moraes

Facial reconstruction of a male Homo sapiens neanderthalensis. The Neanderthal has a striking similarity to modern man and we share 99.5% of our genome, so it has been called a subspecies of Homo sapiens, rather than a separate species. (Forensic reconstruction by Cicero Moraes, via Wikimedia Commons.)

In our present age, women swoon over athletic males, so it's understandable that there would have been cross-breeding between Homo sapiens and the Neanderthal. These subspecies derive from a common ancestor who lived about half a million years ago, with the Neanderthal living in Europe and Asia and Homo sapiens staying in Africa.[3] Such cross-breeding occurred when Homo Sapiens started to leave Africa about 100,000 years ago.[3]

Neanderthal contributions to our present genome aren't concentrated. Different people have different Neanderthal genes, some of which aid against infection.[3] One problem is that, unlike fruit flies, which still cross-breed well after being separated by many thousands of generations, sapiens and neanderthalensis were somewhat incompatible after just a few tens of thousands of generations.[3] This evokes the possibility that some Neanderthal genes were harmful in cross-breeds, and such genes were not passed along to modern man.[3]

However, some problematic genes have passed along to the present day, and these are the subject of a recent study by a large international team of scientists.[4-7] Their analysis is published in a recent issue of Science.[4] Members of the research team are associated with Vanderbilt University (Nashville, Tennessee), the University of Washington (Seattle, Washington), the Mount Sinai School of Medicine (New York, New York), the University of Washington Medical Center (Seattle, Washington), Northwestern University (Chicago, Illinois), the Marshfield Clinic (Marshfield, Wisconsin), the Mayo Clinic (Rochester, Minnesota), the National Institutes of Health (Bethesda, Maryland), The Pennsylvania State University (University Park, Pennsylvania), the Geisinger Health System (Danville, Pennsylvania), Stellenbosch University (Tygerberg, South Africa), and Case Western Reserve University (Cleveland, Ohio).[4]

Different people have different snippets of Neanderthal DNA in their genome. By sampling many modern people, about 20% of the Neanderthal genome can be found, so today's humans on every continent are reservoirs of a varied mixture of archaic and modern DNA.[8-9] Says Svante Pääbo, a paleogeneticist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who did early work on this topic, "The Neanderthal genetic contribution to present-day people seems to have larger physiological effects than I would have naively thought."[5] Interestingly, such archaic DNA is absent from most Africans, since the cross-breeding happened outside Africa.[5]

Tracking how Neanderthal DNA affects modern humans was only possible through use of a medical database called the Electronic Medical Records and Genomics (eMERGE) Network which contains a patient's genetic data and medical data. This allowed correlations to be made between genes and symptoms for 28,416 American adults of European ancestry.[4-6]

What was found is a correlation to such conditions as actinic keratosis (skin lesions from exposure to ultraviolet light), hypercoagulation, tobacco use, and the risk of depression.[4] Hypercoagulation would have been beneficial to Neanderthals, who lived in a dangerous environment, since a rapid healing of wounds would prevent pathogens/a> from entering the body.[5-6] For modern man, however, it results in an increased risk of blood clots and strokes. Blood clots and strokes were not a problem for the Neanderthals, who died young.[5]

Some Neanderthal genes were found to be linked with depression and nicotine addiction.[5-6] Quite a few snippets of Neanderthal DNA were correlated with psychiatric and neurological effects.[6] Other Neanderthal genes relate to an ineffective use of thiamine (vitamin B1), which metabolizes carbohydrates in the intestine. Having such Neanderthal genes might predispose people to malnutrition.[5] Correlates to incontinence, bladder pain, and urinary tract disorders were also found.[5]

Show me where it hurts.

Human maladies associated with Neanderthal DNA.

(Base image from J. Casserius, Tabulae anatomicae LXXIXX, photo number L0022375, from the Wellcome Trust, via Wikimedia Commons.)

Lest you think that all our genetic inheritance from the Neanderthal is all bad, two studies recently published in the American Journal of Human Genetics have found three archaic genes that boost immune response.[5] However, even these immune system boosters have a downside of increased allergies.[5]

Curse of the Neanderthal DNA

References: