Species as Individuals in the Hierarchical Theory of Selection 603
an electronic record of the entire Pavo cristatus genome, and future technology
permitted chemical reconstitution from nucleotides, we couldn't call the resurrected
creature a member of Pavo cristatus, even if the reconstituted object looked and
acted like an extinct peacock of old.
FUNCTIONALITY, OR ORGANIZATION. We expect that, at least in some crucial
ways, the parts of an individual will work together so that the individual functions
in a distinctive and cohesive way. This criterion, though crucial as we will see to
the second set of evolutionary criteria, may be the least important (perhaps even
dispensable) for vernacular definitions. If a bounded object maintained all the other
listed properties, but failed to do anything as an entity (and acted, instead, largely
as a repository of separate parts), we would still call the object an individual,
however inert and uninteresting.
Conventional organisms certainly possess all these properties—as well they
must, for the bodies of complex animals established our vernacular Western
paradigm for the general concept of individuality. Yet note that, even here, at the
point of maximal clarity, some fuzziness and indefiniteness plague every criterion.
Consider human bodies, the inevitable exemplar of the paradigm. Our lives have
reasonably discrete beginnings—but if a true moment could be defined without
ambiguity, then our social and political debates about abortion would require new
terms and engage different issues. Death might seem even more definable and
momentary—but, again, fuzziness and ambiguity plague our definitions, leading to
complex, and often heart wrenching, medical and legal wrangles. Perhaps our
bodies pass the criterion of "sufficient stability" with more clarity. We don't fuse
with others, or rise again from the dead (at least in a material world that science
can adjudicate). We are certainly designed to operate discretely, even if our actions
be dysfunctional. All our chemicals, and most of our cells, undergo periodic
replacement—but I remain myself and continue to look sufficiently like my baby
pictures (though not much like my early embryonic form with tail and gill slits!).
So organisms surely pass muster as individuals. But we encounter problems,
including several classic issues subject to endless discussion in the literature, when
we try to assign individuality at other (particularly higher) levels of the organic
hierarchy. For example, the standard objection to interdemic selection (see pp.
648 - 652) holds that too many demes fail the criterion of "sufficient stability"—for
they may not persist long enough to matter in evolution, and their borders may be
too "leaky" as organisms move in and out in the absence of reproductive isolation
between the parts (organisms) of different demes. All too frequently, demes may
operate, in Dawkin's apt metaphor (1976, p. 36), "like clouds in the sky or dust
storms in the desert... temporary aggregations or federations."
Defenders of classical "group" (i.e. interdemic) selection recognize these
problems of course, and all workable models have been purposely constructed to
overcome such objections by specifying conditions that will permit demes to fulfill
the defining criteria listed above. In fact, the classical empirical issue of our
literature on group selection asks whether demes can