Anthropologist finds high number of developmental anomalies in Pleistocene people

November 6, 2018 by Bob Yirka, report
Examples of developmental abnormalities in Pleistocene people. Left to right: the Tianyuan 1, Sunghir 3 and Dolní V?stonice 15 abnormal femora, Center, top to bottom: the Palomas 23 mandibular "flange", the Rochereil 3 cranial lacuna, the long Sunghir 1 clavicle, the Malarnaud 1 incisor agenesis. Right, top to bottom: the Shanidar 1 sacral hiatus, the Pataud 1 polygenesis, and the Dolní V?stonice 16 cleft palate. Credit: Erik Trinkaus.

Erik Trinkaus, an anthropologist at Washington University, has found what he describes as "an abundance of developmental anomalies" in people that lived during the Pleistocene. In his paper published in Proceedings of the National Academy of Sciences, he describes his study of fossils recovered from several sites in the Middle East and Eurasia, and what he found.

The Pleistocene is the period from approximately 2.6 million years ago to approximately 11,700 years ago—it spans the last Ice Age. Prior research has shown this was also the period during which anatomic modern humans developed and spread outside of Africa. In this new effort, Trinkaus suggests it was also a time during which humans experienced a wide variety of physical deformations. His study consisted of gathering data on 66 fossils recovered from various sites, most of which were from approximately 200,000 years ago. He notes that most of the remains were from young adults and represented several species of Homo. In looking at the physical structure of the fossils, he found an unusually high number of deformities such as bowed arms or leg bones, or misshapen skulls and jaws. Intrigued by the high numbers, he added them up and averaged them among the group under study and compared the results with modern anomalies.

Trinkaus found that among the samples was evidence of 75 abnormalities. He also found that approximately two-thirds of those anomalies showed up in less than 1 percent of modern humans. He also found that the abnormalities came about due to a variety of ailments such as blood disorders or hydrocephaly—but a lot of them could not be traced to a cause. He suggests the number of abnormalities is extremely high for such a small group of fossils.

Trinkaus suggests inbreeding is one of the more likely reasons for such a high of abnormalities—hunter-gatherer groups of the time are believed to have been rather small, increasing the odds of inbreeding. He also suggests that it is possible that individuals with such abnormalities received special treatment during burial, which increased the odds of their remains surviving to the modern age for analysis.

Explore further: Skulls of early humans carry telltale signs of inbreeding, study says

More information: Erik Trinkaus. An abundance of developmental anomalies and abnormalities in Pleistocene people, Proceedings of the National Academy of Sciences (2018). DOI: 10.1073/pnas.1814989115

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2.5 / 5 (2) Nov 06, 2018
In addition to the high probability of inbreeding. I would consider the lack of sophisticated natal care during the period the Hominid brain/skull size was increasing.

Plus, as the hunter-gathers relied upon foraged plants for the majority of their diet? As the packs of wanderers moved into new territories? They would need to learn and relearn what was safe to consume. Where to find and recognize previously unknown edible plants during the changing seasons.

Their ancestors were adapted to the ecology of Africa. Strange environments would stress nutritional requirements.

This hypothesis should be verifiable by analyzing the teeth and bones and when available, corprolites found at campsites.
3.7 / 5 (3) Nov 06, 2018
Prior to the modern era humans outside Africa would generally only encounter fewer than 100 people in their entire lifetimes, most of those would be people who lived within a few days walk of their own territory. Opportunities for outbreeding would have been exceedingly few and far between.
2 / 5 (1) Nov 07, 2018
The isolation of Homininan groups would help explain our ancestors interbreeding with Neanderthals and Denisovans.

If just out of sheer desperate frustration!

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