Smaller social
networks led to Neanderthal extinction
L'estinzione dei Neanderthal forse dovuta a minori capacità aggregative.
Neanderthals' bigger eyes and bodies meant they had less
room in their brains for the higher-level thinking required to form large
social groups, a new study says. The finding could explain why they died out
and Homo sapiens conquered the planet.
|
| The replica of a neanderthall skull is displayed in the new Neanderthal Museum in the northern Croatian town of Krapina [Credit: Reuters] |
Neanderthals lived in parts of Europe, Central Asia and
Middle East for up to 300,000 years but vanished from the fossil record about
30,000-40,000 years ago.
Why they disappeared is one of the
mysteries of anthropology. Theories say they may have been victims of climate
change or were massacred by their H. Sapiens cousins.
Now experts from the University of Oxford and the
Natural History Museum in London suggest the answer could lie in available
brainpower.
Neanderthals were stockier than anatomically modern
humans who shared the planet with them at the time of their demise, but their
brains were the same size, the team write
in the journal Proceedings of the Royal Society B.
As a result, Neanderthals "would have required
proportionately more neural matter" to maintain and control their larger
bodies, they say.
Larger eye sockets
Comparing the skulls of 32 H. sapiens and 13
Neanderthals, the researchers also established the Neanderthals had significantly
larger eye sockets, indicating bigger eyes and visual cortices -
those areas of the brain that regulate vision.
"More of the Neanderthal brain would have been
dedicated to vision and body control, leaving less brain to deal with other
functions like social networking," says Oxford anthropologist and lead
author Eiluned Pearce, a doctoral student.
Among living primates and humans, the size of an
individual's social groups is constrained by the size of specific brain
areas, she says. The larger these areas are, the more connections an
individual can maintain.
The archaeological record seems to support the theory
that Neanderthals were cognitively limited to smaller groups - they
transported raw materials over shorter distances and rare finds of symbolic
artefacts suggest a limited ability to trade.
The ability to organise a collective response
would have been a key to survival when times turned harsh, like during the ice
age, Pearce says.
"If Neanderthals knew fewer people in fewer
neighbouring groups, this would have meant fewer sources of help in the event
of, for example, local resource failure," she says.
"Smaller groups are also more liable to
demographic fluctuations, meaning a greater chance of a particular group
dying out. Smaller groups are less able to maintain cultural knowledge, so
innovations may be more likely to be lost.
"Overall, if Neanderthals had smaller groups ...
this could have led to their extinction along a variety of pathways."
Humans won out
Previous research by the Oxford scientists shows that
modern humans living at higher latitudes evolved bigger vision areas in the
brain to cope with the low light levels.
This latest study builds on that research, suggesting
that Neanderthals probably had larger eyes than contemporary humans because
they evolved in Europe, whereas contemporary humans had
only recently emerged from lower latitude Africa.
"While the physical response to high-latitude
conditions adopted by Neanderthals may have been very effective at first, the
social response developed by anatomically modern humans seems to have
eventually won out in the face of the climate instability that characterised
high-latitude Eurasia at this time," the study concludes.
The relationship between absolute brain size and higher
cognitive abilities has long been controversial, the authors admit.
Their finding, that similar-sized brains had been
differently organised, "could explain why Neanderthal culture appears less
developed than that of early humans, for example in relation to symbolism,
ornamentation and art".
Author: Mariette Le Roux | Source: AFP [March 13, 2013]
