Skulls of early humans carry telltale signs of inbreeding, study says

March 18, 2013
This is a view of the Xujiayao site (below) and internal and external view of the Xujiayao 11 skull piece with its position indicated on the drawing of a complete skull (above). Credit: Erik Trinkaus

Buried for 100,000 years at Xujiayao in the Nihewan Basin of northern China, the recovered skull pieces of an early human exhibit a now-rare congenital deformation that indicates inbreeding might well have been common among our ancestors, new research from the Chinese Academy of Sciences and Washington University in St. Louis suggests.

The skull, known as Xujiayao 11, has an unusual perforation through the top of the brain case—an enlarged parietal foramen (EPF) or "hole in the skull"—that is consistent with modern humans diagnosed with a rare genetic mutation in the homeobox genes ALX4 on and MSX2 on chromosome 5.

These specific interfere with bone formation and prevent the closure of small holes in the back of the prenatal braincase, a process that is normally completed within the first five months of fetal development. It occurs in about one out of every 25,000 modern human births.

Although this genetic abnormality is sometimes associated with cognitive deficits, the older adult age of Xujiayao 11 suggests that any such deficits in this individual were minor.

Traces of , such as EPF, are seen unusually often in the skulls of Pleistocene humans, from early Homo erectus to the end of the Paleolithic.

"The probability of finding one of these abnormalities in the small available sample of human fossils is very low, and the cumulative probability of finding so many is exceedingly small," suggests study co-author Erik Trinkaus, the Mary Tileston Hemenway Professor of Anthropology in Arts & Sciences at Washington University in St. Louis.

"The presence of the Xujiayao and other Pleistocene human abnormalities therefore suggests unusual population dynamics, most likely from high levels of inbreeding and local population instability." It therefore provides a background for understanding populational and cultural dynamics through much of human evolution.

Published March 18 in the journal PLOS ONE, the study is co-authored by Xiu-Jie Wu and Song Xing of the Institute of Vertebrate Paleontology and Paleoanthropology, Beijing. Its findings are based on the analysis of the fossilized partial skull of an adult late archaic human from the Xujiayao site, in the Nihewan Basin of .

Explore further: Handsome by Chance

Related Stories

Handsome by Chance

August 2, 2007

Chance, not natural selection, best explains why the modern human skull looks so different from that of its Neanderthal relative, according to a new study led by Tim Weaver, assistant professor of anthropology at UC Davis.

Modern humans emerged far earlier than previously thought

October 25, 2010

(PhysOrg.com) -- An international team of researchers based at the Institute of Vertebrate Paleontology and Paleoanthropology in Beijing, including a physical anthropology professor at Washington University in St. Louis, ...

New evidence for the earliest modern humans in Europe

November 2, 2011

The timing, process and archeology of the peopling of Europe by early modern humans have been actively debated for more than a century. Reassessment of the anatomy and dating of a fragmentary upper jaw with three teeth from ...

Human skull study causes evolutionary headache

December 20, 2011

Scientists studying a unique collection of human skulls have shown that changes to the skull shape thought to have occurred independently through separate evolutionary events may have actually precipitated each other.

Recommended for you

Early human diet explains our eating habits

August 31, 2015

Much attention is being given to what people ate in the distant past as a guide to what we should eat today. Advocates of the claimed palaeodiet recommend that we should avoid carbohydrates and load our plates with red meat ...

Just how good (or bad) is the fossil record of dinosaurs?

August 28, 2015

Everyone is excited by discoveries of new dinosaurs – or indeed any new fossil species. But a key question for palaeontologists is 'just how good is the fossil record?' Do we know fifty per cent of the species of dinosaurs ...

Fractals patterns in a drummer's music

August 28, 2015

Fractal patterns are profoundly human – at least in music. This is one of the findings of a team headed by researchers from the Max Planck Institute for Dynamics and Self-Organization in Göttingen and Harvard University ...

0 comments

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.