Species as Individuals in the Hierarchical Theory of Selection 601
overemphasize (see Gould and Lloyd, 1999)—functional cohesiveness among their
general criteria of "thingness," a property better captured by "organism" than by
"individual" in vernacular English.
I strongly urge the opposite and more conventional solution. This issue, I fully
recognize, only concerns words, not the empirical world. But we get so muddled,
and waste so much time, when we fail to be clear about words and definitions—
especially when various scholars use the same word in different, or even opposite,
ways—as in the classic confusion generated when molecular biologists began to
use "homology" for the percent of similarity in genetic sequence between two
organisms, rather than for the well-established and entirely different concept of
joint possession due to common ancestry. Fortunately, in this case, we
evolutionists have apparently managed to persuade our molecular colleagues to
respect conventional usage, and to call their important concept "sequence
similarity," or some such.
No one would create such a muddle on purpose, but this particular confusion
already exists—and some common ground must therefore be established if we
wish to address this growing and important literature without a perennial need to
stop, translate, and bear linguistic idiosyncrasies continually in mind whenever we
read a paper. At the moment, most authors use "organism" for the Darwinian body
(me and thee), and "individual" for the generalized unit of selection at any
hierarchical level—while others (like Wilson and Sober) employ reversed
definitions.
I strongly urge the former course—organisms as conventional vernacular
bodies, and individual for the generalized term—for two reasons. First, this
decision represents more common usage, both in vernacular English and among
biologists. (Several academic departments include the phrase "organismic biology"
in their title to defend a continuing focus on entire bodies against molecular claims
for hegemony. But if genes are organisms as well, this ploy will not work!)
Second, the technical definition of an "individual" in academic philosophy, and the
spread of this terminology in the large literature inspired by Ghiselin's arguments
for species as individuals (summarized above), grants priority to "individual" as
the general term, and "organism" as the restricted body. Ghiselin (1974b, p. 536)
clearly defended this usage in his original definition: "In logic, 'individual' is not a
synonym for 'organism.' Rather, it means a particular thing." And Hull (1976, p.
175) explicitly labeled the application of "organism" to higher-level objects as
misleading because vernacular language so strongly equates "organism" with
discrete bodies. He then urged "individual" as the general term, as advocated here:
"From the point of view of human perception, organisms are paradigm individuals.
In fact, biologists tend to use the terms 'organism' and 'individual' interchangeably.
Thus, biologists who wish to indicate the individualistic character of species are
reduced to terming them 'superorganisms.' The same claim can be expressed less
misleadingly by stating that both organisms and species are individuals."
In discussing criteria of individuality, I will focus on species as paradigms for
higher-level evolutionary entities for two reasons: (1) because I believe