A POSITIVE CONCLUSION 355
Cultural evolution can proceed so quickly because it operates,
as biological evolution does not, in the "Lamarckian" mode—by the
inheritance of acquired characters. Whatever one generation
learns, it can pass to the next by writing, instruction, inculcation,
ritual, tradition, and a host of methods that humans have devel-
oped to assure continuity in culture. Darwinian evolution, on the
other hand, is an indirect process: genetic variation must first be
available to construct an advantageous feature, and natural selec-
tion must then preserve it. Since genetic variation arises at random,
not preferentially directed toward advantageous features, the Dar-
winian process works slowly. Cultural evolution is not only rapid;
it is also readily reversible because its products are not coded in our
genes.
The classical arguments of biological determinism fail because
the features they invoke to make distinctions among groups are
usually the products of cultural evolution. Determinists did seek
evidence in anatomical traits built by biological, not cultural, evo-
lution. But, in so doing, they tried to use anatomy for making
inferences about capacities and behaviors that they linked to anat-
omy and we regard as engendered by culture. Cranial capacity per
se held as little interest for Morton and Broca as variation in third-
toe length; they cared only about the mental characteristics sup-
posedly associated with differences in average brain size among
groups. We now believe that different attitudes and styles of
thought among human groups are usually the nongenetic products
of cultural evolution. In short, the biological basis of human unique-
ness leads us to reject biological determinism. Our large brain is
the biological foundation of intelligence; intelligence is the ground
of culture; and cultural transmission builds a new mode of evolu-
tion more effective than Darwinian processes in its limited realm—
the "inheritance" and modification of learned behavior. As philos-
opher Stephen Toulmin stated (1977, p. 4): "Culture has the power
to impose itself on nature from within."
Yet, if human biology engenders culture, it is also true that cul-
ture, once developed, evolved with little or no reference to genetic
variation among human groups. Does biology, then, play no other
valid role in the analysis of human behavior? Is it only a foundation
without any insight to offer beyond the unenlightening recognition
that complex culture requires a certain level of intelligence?