THE MISMEASURE OF MANwrong about the origin of species, but Cuvier's brand of creation-
ism was not an emptier or less-developed world view than Darwin's.
Science advances primarily by replacement, not by addition. If the
barrel is always full, then the rotten applies must be discarded
before better ones can be added.
Scientists do not debunk only to cleanse and purge. They refute
older ideas in the light of a different view about the nature of things.
Learning by debunking
If it is to have any enduring value, sound debunking must do
more than replace one social prejudice with another. It must use
more adequate biology to drive out fallacious ideas. (Social preju-
dices themselves may be refractory, but particular biological sup-
ports for them can be dislodged.)
We have rejected many specific theories of biological determin-
ism because our knowledge about human biology, evolution, and
genetics has increased. For example, Morton's egregious errors
could not be repeated in so bald a way by modern scientists con-
strained to follow canons of statistical procedure. The antidote to
Goddard's claim that a single gene causes feeble-mindedness was
not primarily a shift in social preferences, but an important
advance in genetical theory—the idea of polygenic inheritance.
Absurd as it seems today, the early Mendelians did try to attribute
even the most subtle and complex traits (of apolitical anatomy as
well as character) to the action of single genes. Polygenic inheri-
tance affirms the participation of many genes—and a host of envi-
ronmental and interactive effects—in such characters as human
skin color.
More importantly, and as a plea for the necessity of biological
knowledge, the remarkable lack of genetic differentiation among
human groups—a major biological basis for debunking determin-
ism—is a contingent fact of evolutionary history, not an a priori or
necessary truth. The world might have been ordered differently.
Suppose, for example, that one or several species of our ancestral
genus Australopithecus had survived—a perfectly reasonable scena-
rio in theory, since new species arise by splitting off from old ones
(with ancestors usually surviving, at least for a time), not by the
wholesale transformation of ancestors to descendants. We—that is,