Let
it be said, that biology, dealing with actual palpable furry waddling
entities, would not appear a priori a likely arena of serious
ontological doubts. Physics, by contrast, can’t avoid such scruples,
since it deals largely with the unseen, and postulates just about
everything. Mathematics, freilich: it being (as some would see it) about Being
itself. The only reason, then, that the study of biology figures so
prominently in our remarks, is the extraordinarily high level of
methodological and even philosophical thinking that has been invested in
the evolutionary enterprise, beginning with Darwin himself.
We shall begin, as we love to do, with a quote from Quine:
When
we say that some zoölogical species are cross-fertile, we are
committing ourselves to recognizing as entities the several species
themselves, abstract though they are.
-- Quine, “On What There Is”.
This is true -- indeed, true virtually as a matter of sheer quantificational logic; but its proper biological
content is nil -- as Quine well knows. We may avoid this purely
formal commitment by “so paraphrasing the statement as to show that the
seeming reference to species on the part of our bound variable was an
avoidable manner of speaking.” (The substantive, as the saying goes, can be pegasized away.)
~ ~ ~
In
our essay above-referenced, we focussed on the ontological tug-of-war
between species and gene as the favored stockkeeping unit of evolution.
But whatever the upshot of that, species themselves are obviously
central. Only … what are they?
As so often, Darwin was ahead of the time he himself largely created. Coyne & Orr quote his Origin of Species
(1859): “We shall have to treat species in the same manner as those
naturalists treat genera, who admit that genera are merely artificial
combinations made for convenience.”
And to similar effect:
J.B.S. Haldane observed that “the concept of a species is a concession to our linguistic habits and neurological mechanisms”…
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 11
And again:
Ridley
notes: “The fact that independently observing humans see much the
same species in nature does not show that species are real rather than nominal categories. The most it shows is that all human brains are wired up with a similar perceptual cluster statistic.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 14
Why
are organisms apportioned into clusters separated by gaps? … Dobzhansky
(1935) found this question intractable: “The manifest tendency of life
toward formation of discrete arrays is not deducible from any a priori
considerations. It is simply a fact to be reckoned with.” … While
history can create discrete clusters containing groups of species, we do not see how it can produce species themselves.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 49
Biologists… even questioned whether species exist.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 5
…whether species are real entities or arbitrary constructs of the human mind.
[This is the Nominalist or ‘hocus-pocus’ position. -- dbj] Several
lines of evidence show that species are real. … One asks whether
assemblages of individuals -- populations -- are partitioned into
discrete units that are objective, not subjective.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 7, 10
(To see how far- or over-reaching such scepticism is, for species substitute coffee-cups.)
We
pause to marvel at such self-critical ontological nominalism about the
central practical entities of one’s own discipline. As though:
Dentists: When we speak of ‘teeth’, this is a largely arbitrary demarcation among the hard structures of the body.
Football
coaches: To counterpose ‘offense’ and ‘defense’ is to indulge a false
dichotomy -- which is, however, useful for certain purposes.
Patrolmen’s Benevolent Association: To talk of ‘crime’ is, of course, merely a façon de parler.
Systematists,
whose task is unraveling the history of life, often prefer species
concepts different from those used by evolutionists more interested in
evolutionary processes.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 10
~
~ Posthumous Endorsement ~
"If I were alive
today, and in the mood for a mystery,
this is what I'd be
reading: "
(I am Carl Linnaeus, and I approved this message.)
~
~
~
Another ontological posit:
Cluster analysis distinguished 32 fairly discrete groups in phenotypic space (“phenons”).
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 23
(One’s heart rather sinks, reading this. Recall the profusion of dubious -emes in linguistics.)
… the essential dialectical unity of the biological and the social, not as two distinct spheres … but as ontologically coterminous.
Lewontin, Rose, & Kamin, Not in Our Genes (1984)
~
All species concepts require some subjective judgments.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 34
This, from a pair of very hard-headed writers. Cf. similar points by Keynes in his Treatise on Probability (1921).
Because
we rejected ecological differentiation as part of the Biological
Species Concept in sexually reproducing groups, we obviously endorse the
use of different species concepts in different groups. We do
not consider this pluralism to be a weakness of the BSC. Because the
causes of discreteness may well differ among taxa, so may the concepts
appropriate to addressing the species problem.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 52
Since this astute observation strikes me as very sound, I shall give it a nice name: not Nominalism about species, but Polytypic Realism.
~
Just as it may be no simple matter to posit the right entities, it may not be evident how to ask the right questions:
The
main reason we have had a hard time answering “How many genes cause
postzygotic isolation?” should now be clear: It is not a single
question. Instead, this query masks a large number of questions that
may have very different answers.
Jerry Coyne and H. Allen Orr, Speciation (2004), p. 306
And indeed, the
authors conclude: “There has been nearly endless discussion of species
concepts. This vast and stupefying literature has produced little new
or interesting biology.”
[Update 22 March 2012] And indeed … Andrew Hamilton, reviewing Richard A. Richards, The Species Problem: A Philosophical Analysis, Cambridge University Press, 2010, writes:
There
are four books on my shelf and countless papers in my electronic and
physical files with the title "The Species Problem." Many of these were
written by philosophers, but almost as many were written by biologists. …
None of the books and papers on this topic contains anything like a
consensus solution.
The reviewer then rejects this latest attempt:
As
a solution to 'the' problem or as a theory-based definition, however,
Richards' strategy isn't going to work. … While it may be true … that
all contemporary species concepts pick out population-level evolutionary
lineages, they do so in different and often incompatible ways. Agreeing
that species are lineage segments goes no distance toward helping to
find the boundaries or to settle the host of arguments about what
boundaries to seek. This approach swaps one hard question (what are
species?) for another (what's an evolutionary individual?), as is the
case with most or all of the other proposed solutions to date.
Metasolution:
Having rejected the solution, I would now like to reject the problem.
That, actually, has pretty much been the history of Anglo-Saxon analytic philosophy, from G. E. Moore on out: you don’t solve a problem; you unmask it as metaphysical (or some other handy word), and dissolve it.
[Update 26 May 2013]
Even more radically rejectionist is What Darwin Got Wrong (2011), by
Jerry Fodor and Massimo Piattelli-Palmarini.
The latter author (who largely wrote the former half)
reviews (p. 57) the entities that have been proposed as the axis upon which all
selection turns:
Pleas have been made … for revising
the traditional neo-Darwinian thinking that either the individual, or the
population as a whole, are the sole
units of selection. There
are selective processes … also at the level of genes, chromosomes, whole
genomes, whole epigenomes, cells, developing tissues, kin groups, societies and
communities; and, of course,
organisms and populations.
(Notice that he doesn’t even mention “species”, as in The Origin of Species, yo?)
The former author, laying about him with a broadsword,
writes (p. 126)
Phenotypes aren’t bundles of
traits; they’re more like fusions of traits. Prima facie, the units of phenotypic charge are whole
phenotypes.
Compare the famous hyperholistic thrown-gauntlet of Quine: “The unit of
empirical significance is the whole of science”.
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