A 3D image replica of a 28,000-year-old skull found in France shows it was 20% larger than ours.
Credit: French Museum of Natural History
WASHINGTON: Human brains have shrunk over the past 30,000 years, but it is not a sign of decreasing intelligence, according to scientists who suggest that evolution is making the key motor leaner and more efficient in an increasing population.
The average size of modern humans - the Homo sapiens - has decreased about 10% during that period - from 1,500 to 1,359 cubic centimetres, 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. "I'd called that a major downsizing in an evolutionary eye blink," John Hawks of the University of Michigan said.
Shrinking with the rest of us
The measurements were taken using skulls found in Europe, the Middle East and Asia.
Some anthropologists note that brain shrinkage is not very surprising since the stronger and larger we are, the more grey 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.
Survival mechanism for increased population
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. "As complex societies emerged, the brain became smaller because people did not have to be as smart to stay alive," Geary said.
Are brains shrinking to make us smarter?
Professor Hare says “I hope Bonobos win … it will be better for everyone.”
Hmmmm.
The human animal is what it is because our genome combines elements of both Bonobos and Chimpanzees – not to mention remnants of genomes stretching back to the dinosaurs and to the fishes. These traits manifest themselves in the things that humans do: we war with one another and we take care of one another – and we do both in magnificent fashion.
Our range of behavior and our capacity for good and evil exceeds that of every other creature on Earth by several orders of magnitude. Because the ends of this range are so far apart, we have a very large region in the middle which we humans have learned to exploit – magnificently.
We build empires and civilizations. We build machines that overcome our natural physical limitations; automobiles to allow us to ‘run’ faster, airplanes to give us wings, computers to calculate what our brains cannot, electronic communications to extend the range of our voice, the telescope to extend our vision ever deeper into the universe, the microscope to magnify the tiny creatures living in a drop of pond water, and writing to extend our neurological memory.
The price we pay to own the neurology to feed our insatiable curiosity lurks on one of the range of human behavior, our capacity to do evil.
If, as Professor Hare hopes will happen, the equation of human nature is altered so that we become more bonobo-like and less chimp-like, we would become less human and thus less capable of doing all the ‘magnificent’ things – both good and evil - that humans do.
And besides, our story is not over yet. We are, as we speak, connecting the human brain to computers which will ultimately create an entity that will explore the universe. Humans as we now exist will not go far out there, but our humanity, our intelligence and our insatiable curiosity will. We will digitally encode our DNA and, with robots and robotic laboratories, ship it into the galaxy in search of habitable planets and on those worlds, we will reassemble ourselves.
So, Professor Hare, I hope that you understand that both the Chimps and the Bonobos need to continue their respective tasks within us so that we will remain magnificently human and not wither into something else.