A new study of the famous “Hallstatt
skulls” has raised renewed questions about evolutionary change, according to
Evolution magazine.
Quoting a study completed by researchers at
the Universities of Manchester and Barcelona, the magazine reported that the
evidence indicated that “the human skull is highly integrated, meaning
variation in one part of the skull is linked to changes throughout the skull.”
The researchers examined 390 skulls from
the Austrian town of Hallstatt, part of a famous collection kept in the local
Catholic Church ossuary. A somewhat bizarre local tradition has developed there
that the remains of the town's buried dead are exhumed to make space for more
recent burials.
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," Dr Chris Klingenberg, from Manchester's Faculty of
Life Sciences was quoted as saying.
“We were able to use the genetic
information to simulate what would happen if selection were to favour
particular shape changes in the skull. As those changes, we used the key
features that are derived in humans, by comparison with our ancestors: the shift
of the foramen magnum associated with the transition to bipedal posture, the
retraction of the face, the flexion of the cranial base, and, finally, the
expansion of the braincase.
"As much as possible, we simulated
each of these changes as a localised shape change limited to a small region of
the skull. For each of the simulations, we obtained a predicted response that
included not only the change we selected for, but also all the others. All
those features of the skull tended to change as a whole package.
“This means that, in evolutionary history,
any of the changes may have facilitated the evolution of the others."
Lead author Dr Neus Martínez-Abadías, from
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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