Are brains shrinking to make us smarter?
Bonobo
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Human brains have shrunk over the past 30,000 years, puzzling
scientists who argue it is not a sign we are growing dumber but that
evolution is making the key motor leaner and more efficient.
The average size of modern humans - the Homo sapiens - has decreased
about 10 percent during that period - from 1,500 to 1,359 cubic
centimeters, the size of a tennis ball.
Women's brains, which are smaller on average than those of men, have
experienced an equivalent drop in size.
These measurements were taken using skulls found in Europe, the
Middle East and Asia.
"I'd called that a major downsizing in an evolutionary eye blink,"
John Hawks of the University of Michigan told Discover magazine.
But other anthropologists note that brain shrinkage is not very
surprising since the stronger and larger we are, the more gray matter we
need to control this larger mass.
The Neanderthal, a cousin of the modern human who disappeared about
30 millennia ago for still unknown reasons, was far more massive and had
a larger brain.
The Cro-Magnons who left cave paintings of large animals in the
monumental Lascaux cave over 17,000 years ago were the Homo sapiens with
the biggest brain. They were also stronger than their modern
descendants.
Psychology professor David Geary of the University of Missouri said
these traits were necessary to survive in a hostile environment.
He has studied the evolution of skull sizes 1.9 million to 10,000
years old as our ancestors and cousins lived in an increasingly complex
social environment.
Geary and his colleagues used population density as a measure of
social complexity, with the hypothesis that the more humans are living
closer together, the greater the exchanges between group, the division
of labour and the rich and varied interactions between people.
They found that brain size decreased as population density increased.
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Chimpanzee |
"As complex societies emerged, the brain became smaller because
people did not have to be as smart to stay alive," Geary told AFP. But
the downsizing does not mean modern humans are dumber than their
ancestors - rather, they simply developed different, more sophisticated
forms of intelligence, said Brian Hare, an assistant professor of
anthropology at Duke University.
He noted that the same phenomenon can be observed in domestic animals
compared to their wild counterparts.
So while huskies may have smaller brains than wolves, they are
smarter and more sophisticated because they can understand human
communicative gestures, behaving similarly to human children.
An illustration of the modern human brain. The downsizing does
not mean modern humans are dumber than their ancestors — rather,
they simply developed different, more sophisticated forms of
intelligence, said Brian Hare, an assistant professor of
anthropology at Duke University. – Illustration by Patrick J.
Lynch/ Wikimedia Commons |
"Even though the chimps have a larger brain (than the bonobo, the
closest extant relative to humans), and even though a wolf has a much
larger brain than dogs, dogs are far more sophisticated, intelligent and
flexible, so intelligence is not very well linked to brain size," Hare
explained.
He said humans have characteristics from both the bonobo and
chimpanzee, which is more aggressive and domineering.
"The chimpanzees are violent because they want power, they try to
have control and power over others while bonobos are using violence to
prevent one for dominating them," Hare continued.
"Humans are both chimps and bobos in their nature and the question is
how can we release more bonobo and less chimp.
"I hope bonobos win... it will be better for everyone," he added.
The Hindu |