This insight actually resolves
something else. The Neanderthal skull
supported much stronger jaws than we use.
Is it possible that a switch to a more modernist diet led to a complete
reshaping of the skull and a loss of the brow ridge?
The Neanderthals were generally
more robust than humanity but that plausibly reflected the special conditions
of Ice Age hunter gathering. The ability
to settle down into an easier lifeway could thus easily have brought about the
observed difference. At the least we
need to revisit the assumptions we have held from the beginning.
Could the simple switch to cooked
food lead indirectly to much larger skulls?
Once you establish that changes are all linked together, one may as well
start with the biggest and easiest.
Human skull study causes evolutionary headache
by Staff Writers
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.
Researchers at the Universities of Manchester
and Barcelona
The Austrian skulls are part of a famous collection kept in the
Hallstatt Catholic Church ossuary; local tradition dictates that the remains of
the town's dead are buried but later exhumed to make space for future burials.
The skulls are also decorated with paintings and, crucially, bear the
name of the deceased. The Barcelona
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, in Manchester's Faculty of Life Sciences
"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 Martinez-Abadias, from the University of Barcelona
Martinez-Abadias, N.; Esparza, M.; Sjovold, T.; Gonzalez-Jose, R.; Santos
Hernandez, M.; Klingenberg, C.P. "Pervasive genetic integration
directs the evolution of human skull shape". Evolution, November 2011,
DOI: 10.1111/j.1558-5646.2011.01496.x
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