Expert: John Shea - 1/15/2010

Question
THOUGH THE CROMAGNON MEN HAD A BRAIN CAPACITY OF 1650cc, WE HAVE THE CAPACITY OF 1450CC.WHY OUR BRAIN CAPACITY IS LESS THAN THAT OF CROMAGNON?

Answer
It probably reflects a scaling relationship wiht body size and climate.  Cro-Magnons were big, strong people who lived in a cold climate.
These are factors that predict marginally larger brain sizes among mammals.
Most living humans dwell in tropical latitudes (think, equatorial Africa, south Asia, China), so the average for living humans is relatively low,
mainly because there are a lot of people living in the tropics today.  (Same was probaby true back in Cro-Magnon times, but for a variety of reasons
people tend to treat "Cro-Magnons" as "typical" of Pleistocene humans.  (They aren't, they are just better-known that equally-ancient fossils from other regions
but that's a whole different issue.)
It probably doesn't reflect raw intelligence because brain size variation among (non-pathological) living humans isn't a strong predictor of
intelligence.
Sincerely
John Shea