Blog dedicated primarily to randomly selected news items; comments reflecting personal perceptions

Friday, January 31, 2014

Linking Genes

"The researchers also find parts of the human genome that are deficient in Neanderthal alleles (bits of DNA), implying active removal during evolution."
"This result suggests that Neanderthal DNA reduced male fertility when transferred to a modern human genetic background, and these incompatibility alleles were therefore eliminated."
Harvard Medical School study, published in journal Nature

Most people whose ancestors are from Europe or Asia inherit 1% to 3% of their genes from Neanderthals — heavy-set, early humans that have been extinct for roughly 30,000 years.
Pierre Andrieu/AFP/Getty Images    Most people whose ancestors are from Europe or Asia inherit 1% to 3% of their genes from Neanderthals — heavy-set, early humans that have been extinct for roughly 30,000 years.
So, one can suppose that the hypothesis that held sway decades ago that female Homo sapiens could never carry Neanderthal-fathered babies to full term because of the size of the baby's cranium -- causing death in childbirth to both mother and child -- and that Neanderthal females had no problems carrying to full term resulting in birth babies fathered by Homo sapiens males since no such difficulty arose as they were physically broader (and Homo sapiens' cranium was smaller), is not the issue here.

Although the article does speak of issue, as it happens. The issue being the minuscule provenance of modern humankind with its three percent of genes inherited from those primitives called Neanderthals, early human prototypes who lived in the last Ice Age in Central Asia and Europe, and who haven't been seen anywhere since, for the past 30,000 years. But for the minuscule remnants that remain within populations whose ancestors were originally from Europe or Asia.
A new genetic analysis produced by scientists with the Harvard Medical School, has produced a study hypothesizing that no active genes were left in modern men in two areas, resulting from Neanderthal primitive heritage. No genes were passed down expressing themselves (seen to be present) in the testes. The modern male reproductive mechanism is absent Neanderthal presence. Which, they point out, owes its presence to Homo sapiens' genetic influence.

The study authors consider this to be a classic instance of "hybrid sterility", seen most clearly and popularly in horse-donkey matings producing mules, very nice animals, but incapable of reproducing. Cross-breeding leading to sterility. And so it is with the breeding cross between Homo sapiens and Neanderthals away back when, according to these geneticists. Evolution, they point out, halts carriers of specific genes from reproducing.

According to Earl Brown, a geneticist with the University of Ottawa, the Neanderthal inheritance would have meant random gene selection scattered across human chromosomes. Some offspring might have the capacity to reproduce and some would not, eventually causing an editing-out of sex-related male genes. What did we inherit then from Neanderthal forefathers/mothers? A sharing of some hair and skin genes.

Interpreted by geneticists as an evolutionary advantage -- to avoid having African hair and skin in the cool climate of a Europe that is sun-deprived, unlike the Continent of Africa, where dark skin was an evolutionary protection against the ravages of human skin exposed to hot, relentless sun. It's still up in the air how much cerebral grey matter was inherited through the Neanderthal link, though. Once thought to be mulishly dull, they've since been brain-washed, so to speak.

New findings have been discovered to rehabilitate their image, so forget about calling your brutish neighbour a Neanderthal; the insult no longer works within the scientific community where cave paintings and tools were discovered to have been the work of Neanderthals.

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