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 forty 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.
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