Today, we get a radiator for our brains. The University of Houston's College of
Engineering presents this series about the machines that make our civilization run, and
the people whose ingenuity created them.
Braindance is the odd title of Dean Falk's recent
book on human evolution. She offers new means for dealing with the old issue of how modern
humans finally emerged, some 30,000 years ago. Falk begins four and a half million years
ago with the species Australopithecus, first discovered in South Africa in 1924.
In those days, paleontologists shied away from controversy with anti-evolutionists by
classifying anything that might be our ancestor as human. That's how a major
anti-evolution myth grew up -- the myth that we couldn't find the missing link.
Australopithecus did walk on its hind legs. But there its humanity ends. Its brain was
the same size as a chimpanzee's -- about a third the size of yours. Falk believed the
brain of that not-so-missing link was the key to the puzzle.
She found structures in Australopithecus's brain that were apelike, not human. Here was
a creature who walked upright with hands free for two million years, yet it was endowed
with the brain of an ape. The famous Lucy skeleton was one of these.
Then, a little over two million years ago, our ancestor's brain began growing. It took
on the folds and creases of your brain or mine. A species called Homo habilis had a 40
percent larger brain. By 1.5 million years ago, Homo erectus was walking the hot plains of
Central Africa with a brain more than double the size of Australopithecus's -- who was
still around, it seems.
Falk struggled to understand what had happened. Then, something emerged from her
subconscious. One day her car mechanic had told her, "The size of your car's engine
is limited by the capacity of its radiator to cool it." That was it! The brain is
terribly sensitive to changes in temperature. It absolutely must be cooled in summer and
heated in winter. But where is its radiator? Falk began studying the blood supply to
ancient brains.
Sure enough: along with changes in brain size ran an evolving blood delivery system.
When Lucy took to her hind legs, her head had to bear the brunt of the African sun. She
began changing, very slowly. More holes appeared within humanoid skulls to provide access
for more blood to cool the brain. The radiator of a Model-T evolved into the radiator of
your Rolls-Royce brain.
It was 125,000 years ago that our brains reached their full modern size in, of all
people, the Neanderthals. They began creating art, building huts, burying their dead, and
worshipping deities. They weren't toilet trained, it seems, but then -- if you look at our
lakes and rivers -- maybe we aren't either. But now we had our radiator and now the real
fun was about to begin.
I'm John Lienhard at the University of Houston, where we're interested in the way
inventive minds work.
(Theme music)
Falk, D., Braindance: New Discoveries About Human Origins and
Brain Evolution. New York: Henry Holt and Company, 1992.
Photo by John Lienhard
Representation of Homo Habilis at the University of New Mexico Anthropological Museum
