Punctuated Equilibrium and the Validation of Macroevolutionary Theory 913
"Evolution of Humans May at Last Be Faltering." The opening sentence reads:
"Natural evolutionary forces are losing much of their power to shape the human
species, scientists say, and the realization is raising tantalizing questions about
where humanity will go from here." (Professionals should always become
suspicious when we read the universal and anonymous justification, "scientists
say.")
These stories begin from the same foundational fallacy and then proceed in an
identically erroneous way. They start with the most dangerous of mental traps: a
hidden assumption, depicted as self-evident, if recognized at all— namely, a basic
definition of evolution as continuous flux. Under this premise, the correct
observation that Homo sapiens has experienced no directional trending for at least
40,000 years seems outstandingly anomalous. Reporters therefore assume that this
unique feature of human evolutionary history requires a special explanation rooted
in mental features that we share with no other species. They then generally assume,
to complete the cycle of false argument, that human culture, by permitting the
survival of marginal people who would perish in the unforgiving world of raw
Darwinian competition, has so relaxed the power of natural selection that
evolutionary change (popularly defined as "improvement") can no longer occur in
Homo sapiens. This situation supposedly raises a forest of ethical questions about
double-edged swords in the cure of diseases arising from genetic predisposition,
the spread of genes for poor vision in a world of cheap eyeglasses, et cetera ad
infinitum. (Pardon my cynicism based on some knowledge of the history of such
arguments, but the neo-eugenical implications of these claims, however unintended
in modern versions, cannot be ignored or regarded as just benignly foolish.)
This entire line of fallacious reasoning, with all its burgeoning implications,
immediately collapses under a speciational reformulation. Once people understand
Homo sapiens as a biological species, not a transitory point of passage in the
continuous evolutionary progression of nature's finest achievement, the apparent
paradox disappears by conceptual transformation into an expectation of
conventional theory. Most species—especially those with large, successful, highly
mobile, globally spread, environmentally diverse, and effective panmictic
populations—remain stable throughout their history, at least following their origin
and initial spread, and especially under the model of punctuated equilibrium that
seems to apply to most hominid taxa. Change occurs by punctuational speciation of
isolated subgroups, not by geologically slow anagenetic transformation of an
entirety.
So if speciation usually requires isolated populations, how (barring science
fiction scenarios about small groups of people spending generations in space ships
hurtling towards distant stars) can a global species like Homo sapiens, endowed
with both maximal mobility and an apparently unbreakable propensity for
interbreeding wherever its members travel, ever expect to generate substantial and
directional biological change in its current state? Most species should evoke
predictions of stability, but Homo sapiens must lie at an extreme end of confidence
for such an expectation. Thus, there is no solution to