704 THE STRUCTURE OF EVOLUTIONARY THEORY
I presented the case for treating species as individuals in an earlier section of
this chapter (pp. 603-608), noting that punctuated equilibrium greatly aids such a
delineation, but then extending and generalizing the argument by holding that
species can be individuated under any scheme that depicts their origin as an event
of branching, rather than anagenetic transformation. Critics of this view,
particularly Williams (who does not dispute the truly necessary claim for origin by
branching), continue to raise standard objections, especially "an absence of a
decisive beginning for a species" (Williams, 1992, p. 121). But Williams, in
advancing this argument, commits the classic error of failure to appreciate proper
scales. His claim for fatal fuzziness in origins views the question from a
generational perspective at the scale of human lifetimes. The great majority of
species, however, arise in geological moments (thousands of years, and thus overly
long only at the inappropriate scale of our personal lives)—a shorter period of
ambiguity (relative to later duration as a clearly separate entity) than we note for
most asexual organisms that reproduce by budding (the proper organismic analog
for the origin of a new species by branching)!
Most other published objections to species as individuals also express little
beyond our psychological difficulty in making a transition to different criteria at
unfamiliar scales. Some critics have argued, for example, that species can't develop
the requisite property of heritability, because no mechanism can be analogized
with the well-known Mendelian basis for this phenomenon at the organismic level.
But heritability measures the correlation between parents and offspring based on
direct transmission of formative properties—and daughter species surely inherit
parental characteristics by this standard route. The required correlation arises by
transmission of autapomorphic characters through retained homology—the
appropriate mechanism of heritability at this higher scale, and in no way "worse"
than Mendelian criteria for the construction of organisms. Moreover, species
heritability can be measured in the same general way, and with the same potential
accuracy, as standard organismic heritability—as Jablonski (1987) has done in our
best-recorded case of species selection for the evolution of marine mollusks in
normal times and episodes of mass extinction.
Other critics charge that species are too spatially diffuse, or too lacking in
mechanisms of internal coherence, to count as individuals. But, again, these
arguments only arise from failure to conceptualize this different scale in an
appropriate manner—a mental foible rooted in our parochial allegiance to the
particular (and poorly-scaling) criteria of individuality for organisms. Species don't
build a physical skin, but reproductive isolating mechanisms maintain their borders
just as sharply. Species don't evolve immune systems and other forms of "policing"
against outside invaders, but the constant admixture among their parts via sexual
reproduction maintains coherence with more than adequate force.
SPECIES AS INTERACTORS. This more interesting and challenging argument has
unfolded among supporters of macroevolutionary theory as an "in-house"