Species as Individuals in the Hierarchical Theory of Selection 613
p. 55) writes, for example: "The reason must be that communities lack the
necessary high rates of reproduction and replacement and especially the high level
of heritability required for effective selection. They change their makeup so rapidly
that selection among communities must be overwhelmed by endogenous change."
But these principled exclusions leave us with a rich hierarchy of legitimate
biological individuals, all related by the fascinating property of nested inclusion
within evolution's genealogical system. In appropriate circumstances, broad
enough for vital agency in the evolution of life on earth, individuals at many
levels—including genes, cell lineages, organisms, demes, species, and clades—can
act as units of Darwinian selection. I doubt that we can defend any longer—or as
any more than a convenient and parochial preference based on the happenstances
of size and duration for a human body—the central Darwinian conviction that
organisms represent the fundamental level of Darwinian individuality, with all
other levels either nonexistent, impotent, entirely subservient, or operating only in
odd and restricted circumstances.
The Evolutionary Definition of Selective Agency and the
Fallacy of the Selfish Gene
A FRUITFUL ERROR OF LOGICScience thrives upon the continuous correction of error. Most errors arise from
inadequate knowledge of the empirical world, or (if grounded in a theoretical
prejudice) at least persist because we have no means (conceptual or technological)
to secure their empirical refutation. For example, we once lacked the technology to
prove that buried organic matter might petrify, and that wood made of stone might
therefore represent the remains of ancient plants, and not the power of rocks to
mimic organic design by a process analogous to crystallization.
Only rarely, however, do professions get sidetracked by pursuing an extensive
and long-lasting program of research initiated by an error in reasoning rather than
an inadequacy of empirical knowledge. Yet I think that the gene-centered approach
to natural selection—based on the central contention that genes, as persistent and
faithful replicators, must be fundamental (or even exclusive) units of selection—
represents a purely conceptual error of this unusual kind. In beginning with
Williams's manifesto (1966)—based on a mode of thinking rooted in the brilliantly
consistent, if limited, worldview of R. A. Fisher (1930), but immediately inspired
by the remarkable work of W. D. Hamilton (1964)—and proceeding through the
codification of Dawkins (1976), to numerous works both popular (especially
Cronin, 1991) and technical (Dennett, 1995), this gene-based approach to selective
agency has inspired both fervent following of a quasi-religious nature (see R.
Wright, 1994), and strong opposition from many evolutionists, who tend to regard
the uncompromising version as a form of Darwinian fundamentalism resurgent
(see Gould, 1997'd), variously designated as ultradarwinism (Eldredge, 1995) or
hyperdarwinism.