Punctuated Equilibrium and the Validation of Macroevolutionary Theory 785
tine as both unlikely and too difficult to test in any case—explanation of the
punctuational pattern as a consequence of speciation scaled into geological time.
If we accept that temporal sequences of fossils generally don't appear in the
geological record as unbreakable continua, but usually as morphological
"packages" with reasonably defined boundaries and sufficient stability within an
extended duration, how can we assert that these packages represent biospecies, or
at least that they approximate these neontologically defined units with sufficient
closeness to bear comparison? After all, we cannot apply conventional tests of
observed ecological interaction or interbreeding to fossils—and, whereas
biospecies may be recognized by morphological differentia in everyday practice,
they are not supposed to be so defined. Can the temporally extended
"morphospecies" of paleontology really be equated with the "nondimensional
species concept" (Mayr's words) of neontology?
I certainly accept the centrality and difficulty of these issues, but I do not
regard them as insuperable, and I do not view the species concept as untestable
with fossils. After all, the overwhelming majority of modern species in our
literature and museum drawers have also been phenotypically, not ecologically,
defined. Once we accept that no special paleontological riddles arise from the
Scheinproblem of temporal continua, and then most paleospecies have been no
worse characterized than the majority of neospecies. Still, I will not advance this
excuse as exculpatory for the fossil record, for a neontologist could reply, with
impeccable logic, that neospecies so defined should also be regarded as uncertain,
if not vacuous, and that no paleontological defense can be mounted by arguing that
ordinary practice with fossils follows the worst habits (majoritarian though they
may be) of neontological taxonomy.
But a best defense of phenotypically defined neospecies would follow from
demonstrations that taxa so established usually do match true biospecies upon
proper behavioral and ecological study—a line of research often pursued with
success (see references in Jackson and Cheetham, 1994, and in Jablonski, 1999).
Similarly, my main source for confidence about paleospecies arises from proven
correspondences with true biospecies in favorable cases providing sufficient
information for such a test (particularly for extant species with lengthy fossil
records). I do not, of course, argue that all named paleospecies are true biospecies,
or that I can even estimate the percentage properly so defined (any more than we
know the relative frequency of modern taxa that represent true biospecies). But I
do not see why the probability that well-defined paleospecies, based on good
collections from many times and places, might represent proper biospecies should
be any lower than the corresponding figure for equally well documented, but
entirely morphologically defined, modern taxa. (In fact, one might argue that well-
documented paleospecies probably maintain a higher probability for representing
biospecies, because we know their phenotypes, and have measured their stability,
across long periods of time and wide ranges of environment—whereas modern
"morphospecies" may arise as ecophenotypic expressions of a single time