Human skull `highly integrated`

London: Scientists have claimed that human skull is highly integrated, meaning variation in one part of the skull is linked to changes throughout the skull.

In fact, a team from the Universities of Manchester and Barcelona, studying a unique collection of human skulls, have shown that changes to skull shape thought to have occurred independently through separate evolutionary events may have precipitated each other, the `Evolution` journal reported.

For their study, the researchers examined 390 skulls from the Austrian town of Hallstatt and found evidence that the human skull is highly integrated, meaning variation in one part of the skull is linked to changes throughout the skull.

The Austrian skulls are part of a famous collection kept in the Hallstatt Catholic Church ossuary; the skulls are also decorated with paintings and, crucially, bear the name of the deceased.

The Barcelona team made measurements of the skulls and collected genealogical data from the church`s records of births, marriages and deaths, allowing them to investigate the inheritance of skull shape.

The team tested whether certain parts of the skull --the face, the cranial base and the skull vault or brain case-- changed independently, as anthropologists have always believed, or were in some way linked.

The scientists simulated the shift of the foramen magnum (where the spinal cord enters the skull) associated with upright walking; the retraction of the face, thought to be linked to language development and perhaps chewing; and the expansion and rounding of the top of the skull, associated with brain expansion.

They found that, rather than being separate evolutionary events, changes in one part of the brain would facilitate and even drive changes in the other parts.

"We found that genetic variation in the skull is highly integrated, so if selection were to favour a shape change in a particular part of the skull, there would be a response involving changes throughout the skull," said Dr Chris Klingenberg of Manchester University, a team member.

He added: "We were able to use the genetic information to simulate what would happen if selection were to favour particular shape changes in the skull."

Team leader Dr Neus Martinez-Abadias at the University of Barcelona added: "This study has important implications for inferences on human evolution and suggests the need for a reinterpretation of the evolutionary scenarios of the skull in modern humans."


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