Thursday, 21 March 2013

Skulls of Early Humans Carry Telltale Signs of Inbreeding


Mar. 18, 2013 — 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 chromosome 11 and MSX2 on chromosome 5.
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/WUSTL)

These specific genetic mutations 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.


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