Race, Brain Size, and IQ

J. Philippe Rushton (RUSHTON@SSCL.UWO.CA)
Sun, 30 Oct 1994 21:02:43 -0500

much more intra-racial variation in all races than there is inter-racial
variation on all traits, even skin color. IQ test scores range from
retarded to genius in all races. On molecular genetic measures the African
populations have the most variability of all, indicating they are the
evolutionary oldest because they have had more time to allow mutations
to develope. Mongoloid populations have the least amount of genetic
variance suggesting they are the most recently split-off group with
the least time for mutations to accumulate. The ordering in time of
Negroid/Caucasoid/Mongoloid conforms also to the ordering in brain
size and IQ.

However it is an often made mistake to think that because there is
enormous variation within groups that significant and reliable group differencescannot emerge. Of course, they can and do, all the time. Consider
height in men and women. Men average taller than women but there is
enormous variation in height within men and women. Danish women are taller
than Yanomamo men but this does not alter the average male>female ordering
in height.

As for brain size and IQ scores this has been found separately
within all male/female African/European/Asian groups so far studied.
The most recent study on British white male soldiers used magnetic
resonance imaging (MRI) to assess brain size and standard IQ tests
and found a 0.66 correlation (correccted for this and trhat). Appears
in the 1994 October issue of Personality and Individual Differences
by Vincent Egan and colleagues.