Has creeping consanguinity contributed to the high rate of skeletal deformities in early man? | Smart News

A new analysis of 66 human remains revealed 75 abnormal skeletal abnormalities ranging from femur and bones in the malformed jawbone to dwarfism and a case of swelling compatible with hydrocephalus, a condition characterized by the accumulation of liquid in the skull.

This surprisingly high rate of birth defects is probably representative of all ancient populations, says paleoanthropologist Erik Trinkaus of the University of Washington in St. Louis in a new article published in the Proceedings of the National Academy of Sciences. As he says Science In Michael Price magazine, the chances of finding so many anomalies in such a small sample are "quite small."

Trinkaus argues that the skeletons – which date back to around 200 000 years ago and were found in areas as far apart as China, the Czech Republic, Italy and Israel – testify to the widespread cultural and environmental pressures suffered by our Pleistocene predecessors.

Maybe pregnant women have not followed a healthy diet, leaving their offspring susceptible to present skeletal disorders such as rickets. More elaborate burials may have been given to individuals with anomalies, increasing the chances of their conservation and future rediscovery. (Although this is worth noting, Cosmos"Andrew Masterson says that Trinkaus has not found evidence of the use of different funeral practices for people with or without flaws.) It is also possible that hunter-gatherer life has been a challenge without Cease: As the study notes, "The abundance of developmental abnormalities among Pleistocene humans, the generally high stress levels observed in these foraging populations may have had a positive effect. "

According to Hallie Buckley, a bioarchaeologist at the New Zealand University of Otago, the most likely culprit is endemic consanguinity among older populations, who did not participate in the new study. Given the limited size and relative isolation of early human communities, as evidenced by the low level of genetic diversity found in previous studies on ancient DNA, Buckley tells Price that " this seems the most likely explanation.

Some of the abnormalities identified by Trinkaus are hereditary conditions, which makes them more likely to develop in children of closely related individuals. According to the study, many people persist to date, appearing in recent human samples as "unusual but not exceptional" conditions. Others are "extremely rare" in contemporary populations and therefore unlikely to be in the fossil record.

Based on comparisons with modern humans, Trinkaus found that the odds of identifying more "typical" abnormalities among early populations were about five percent. The chances of identifying one of the rarest abnormalities were as low as 0.0001%.

"The chances of finding them in combination or collectively in all relics discovered and dated reliably are astronomical," says Masterson. Cosmos.

The presence of deformities in the ancient remains is not surprising in itself, he adds, but becomes significant instead of the considerable number observed in only 66 sets of remains.

However, Siân Halcrow, a bioarchaeologist from the University of Otago who did not participate in the study, tells Science'S's Price, extrapolating estimates of the incidence of abnormalities among primitive men based on similar numbers in modern populations could be problematic. A better approach would be to compare past obvious rates in the sample with data from prehistoric populations or early history – a difficult task complicated by the fact that such data pools do not yet exist.

Trinkaus was not able to directly identify the causes of the 75 identified anomalies, but, he concludes in the study, there was probably a range of factors, not just one, at stake: "A significant number of these anomalies reflect anomalies or anomalies. development process, whether as a result of genetic variants that alter development processes or as products of environmental or behavioral stress patterns that alter expected patterns of development. "

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