914 THE STRUCTURE OF EVOLUTIONARY THEORY
the supposed paradox of human stability because there is no problem. Homo
sapiens has been stable for tens of thousands of years, and any proper
understanding of macroevolution, as a speciational process must yield this very
expectation.
The same resolution applies to the extensive, and almost preciously silly,
literature on human biological futures. (I do not speak of the real issues sur-
rounding genetic engineering as an interaction of culture and nature, but of the
fallacious and conjectural scenarios that treat presumptive human futures under a
continuing regime of natural selection.) We have all seen reconstructions of
improved future humans with bigger brains and disappearing little toes (perhaps
balanced by the calloused butts of perennial couch potatoes). We also note the
same features in reconstructions of advanced extraterrestrial aliens like ET, and in
conjectural restorations of the hyper-brainy bipedal dinosaurs that might now rule
the world if a bolide hadn't struck the earth 65 million years ago.
Again, this entire theme is moonshine. The only sensible biological prediction
about human futures envisions continued stability into any time close enough to
warrant any meaningful speculation. In any case, cultural change, in its explosive
Lamarckian mode, has now so trumped biological evolution, that any directional
trend in any allelic frequency can only rank as risibly insignificant in the general
scheme of things. For example, during the past ten thousand years, any distinctive
alleles in the population of native Australians must have declined sharply in global
frequency as relative numbers of this subgroup continue to shrink within the
human population as a whole. At the same time, cultural change has brought most
of us through hunting and gathering, past the explosive new world triggered by
agriculture, and into the age of atomic weaponry, air transportation and the
electronic revolution, not to mention our prospects for genetic engineering and our
capacity for environmental destruction on a global scale.
We have done all this, for better or for worse, with a brain of unaltered
structure and capacity—the same brain that enabled some of us to paint the caves
of Chauvet and the ceiling of the Sistine Chapel. What could purely biological and
Darwinian change accomplish, even at a maximal rate (a mere thought experiment
in any case, since we can only predict future stability for the short times that can
justify any reasonable claims for insight), in the face of this explosive cultural
transformation that our unchanging brains have unleashed and accomplished?
- The conventional rate (and unconventional mode) of supposedly rapid
trends traditionally cited as testaments to our uniqueness. When we recognize that
human evolution occurred largely by differential success and replacement among
species within a phyletic bush—and not by anagenetic transformation in measures
of central tendency for a single, coherent entity in constant flux—then almost
every standard claim about the tempo and mode of this process must be
reformulated, and often substantially revised. My first two examples treated broad
issues of maximal public attention. I now close this section with a smaller, but
stubbornly persistent, error in order to clarify