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> ...or maybe naming species is pointless, if our ultimate goal is
> reconstructing the evolutionary history of individuals (the only truly
> non-arbitrary units in evolutionary biology--and that only in organisms
> incapable of asexual reproduction!)
AAAAAAAAAAAAARGH! Oh, wait, this battle is going on on a different list... I
haven't had to go through this on THIS list for a couple months. Sorry...
return to civil tone... :)
Indistinct does not equal arbitrary. Most biologists have rejected
essentialism, and yet they have not rejected the part-in-parcel insistance on
absolutes. We no longer insist that an entity must have an "essence," but many
people embrace the (possibly) related idea that entities (real or imagined)
*must* have an absolute, discrete boundaries. It is fairly clear that nature is
not forthcoming with discrete boundaries. The "natural" conclusion is that the
entities in question are therefore "not real." For example, ring species,
fertile hybrids and cryptic species are often used as examples of the "failure"
of the boundaries of species.
On the other hand, if we accept that boundaries are not real, our
insistance upon their necessary association with a recognized entity condemns
that entity to unreality a priori of consideration. In other words, if you
insist on finding a boundary, you *cannot* find a real entity. Thus,
explorations of the arbitrary nature of species proceed from a fallacious
If any entity is to considered real, we must then admit to the notion
of "fuzzy" boundaries. If unity and natural processes give division, than
entities can only be divided to the extent that nature divides them, and our
ability to recognize those divisions be damned. If we seek "reality," we cannot
insist that it be limited to the "boundary" between matters within and beyond
This consideration extends well BEYOND species, to individuals themselves.
Contrary to what Nick wrote about, individuals (and individuality) are by NO
means necessarily "real" ("non-arbitrary" in Nick's phrasing) in the
conventional wisdom of modern science. Troubling questions can been raised
concerning the individuality of gametes (compare a single vertebrate sperm with
the haploid stage in the life cycle of many non-animals), colonial organisms
(not all of which are necessarily, or even functionally, asexual), the
component cells of metazoans (is a mitochondrion an individual?), etc.
There is a substantial literature regarding the reality of species. A
recent, and, in my view, progressive, synthetic theory has been presented by de
Quieroz in several papers (see references below). Th bibliographies of these
papers offer a good introduction into the broader question of species.
De Queiroz, K. 1998. The general lineage concept of species, species
criteria, and the process of speciation, pp.57-75. In, D. J. Howard and S.
H. Berlocher (eds.), Endless Forms: Species and Speciation. Oxford
University Press, Oxford.
De Queiroz, K. 1999. The general lineage concept of species, species
criteria, and the process of speciation, pp.49-89. In, R. A. Wilson (ed.),
Species: New Interdisciplinary Essays. Massachusetts Institute of Technology