Skulls of early humans reveal evidence of inbreeding

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 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.

These specific genetic mutations interfere with bone formation and prevent the closure of small holes in the back of the prenatal brain-case, a process that is normally completed within the first five months of foetal 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 genetic abnormalities, such as EPF, are seen unusually often in the skulls of Pleistocene humans, from early Homo erectus to the end of the Paleolithic.

- The Independent