Why, you big silly. I just did. "A species is simply whatever categorization
we find convenient for a certain level of thought and discourse...." That's
my theory of what a species is. I predict, based on that theory that no
fixed definition will be found because it varies so much from context to
context. It's a term like "game." It's really a kind of super-concept of
method, a kind of "variable," that shifts meaning from context to context,
according to the needs of the thinker/speaker. In the *world*, there are no
species except broadly (dogs are different from birds, etc.).
>
> > The "problem" is the result of Really Bad Epistemology, not a
> > *biological* problem. It is a problem about the nature and use of
> > concepts. "Species" is a word like "large." It is contextual. Just
> > as "large" in one context might mean as big as a proton, it might
> > mean as big as a trillion times our apparent Universe in another
> > context. We designate what is and is not a species on the basis of
> > cognitive usefulness, not on the basis of some magical actual
> > difference between species.
>
> You are making a case here for "species" being a non-scientific term -
> just a term of popular convenience.
Not quite either. It's term of cognitive and communicational convenience. In
one context, we might say that it means a genetic grouping of organisms that
cannot interbreed with "adjacent" genetic groupings. In another context, we
might say that it means a genetic grouping that merely *does* not interbreed
with adjacent genetic groupings. In still another context, we might say that
it means a genetic grouping of organisms that are simply not sufficiently
differentiated among themselves for the group to be considered to be two or
more genetic groupings.
In a sense, you're right. It's not a scientific term, if you mean scientific
in the same way that the term "atom" is a scientific term. Atoms, with very
few exceptions, *do* form a distinct logical grouping, and the different
"species" of atoms are *also* truly distinct (even isotopes within an
element are each discretely distinct from the other isotopes of the "same"
element). But, though *some* biological distinctions seem vairly deep, the
term "species" does not seem, generally, to be such a term. Is the human
race a species? Are "races" within the human race species? I think that in
most contexts, we would say that the human race is a species, but not
causasian, negroid, mongoloid, etc. But this is a matter of evolutionary
history. As far as evolutionary *theory* goes, there could easily be an
almost perfecly continuous range of gradations between us and "nearby"
primates.
Consider sand dunes. In some places, the sand is built up into little hills,
in others, there are little valleys. But the sand can shift so that the
arrangement of hills and valleys can be completely different. If you picked
one hill initially, and labeled it as a "species," that "species" might
disappear as the sand moved into the space where a valley had been, grain by
grain. The term "species" as applied in this case would be a term of
cognitive convenience for talking about the hills.
Similarly in the "landscape" of life. The human race is one hill at the
moment, but it is not truly sharply separated from other hills on the other
sides of adjacent valleys. In fact, there are probably a monstrously huge
number of possible intermediate genetic paths between us and other primates,
going back, if necessary, to common ancestors and working back up.
The hills and valleys in both cases are essentially temporary local maxima,
with no *essential* boundaries between them and hills that might be present
earlier or later with slightly different maxima.
To reduce the metaphor to two dimensions, think of a graph showing a
vertical *cross-section" through an area of sand dunes: A roughly horizontal
wavy line. If you pick one of the high points, and call it a species, does
that really mean much? No, because, later that high point may be gon and
another one may be nearby but with its "hill" overlapping the place where
the first "hill" had been.
>
> > If Jones is "humming and ha-ing and spluttering," it's not because
> > the concept is difficult, but because he is thinking about it
> > wrongly. In fact, evolutionary theory suggests that speciation would
> > be about what it is, that the only cases where "adjoining" species
> > would really be kept apart would be cases where genetics or
> > environment *keep* them apart, like the arctic terns. Speciation
> > simply proceeds until it reaches a locally-viable maximum for the
> > organisms involved. If there is enough of the certain kinds of
> > culling, we will get species that differ from each other in "larger"
> > ways. If there is usefulness in a more finely-grained speciation,
> > then, speciation will continue up to the limits of
> > distinguishability, causing biologists with Platonic epistemological
> > theories some discomfort, but not bothering the more reality-oriented
> > ones a bit.
>
> This does not explain why there are the "lumpers" and the "splitters"
> in taxonomy. If the term is non-scientific, you are closer to Steve
> Jones than you think. If it is a scientific term, a definition is
> needed. This is where the problem starts.
No, it does not explain that, I agree. *That* is a different question, and I
don't think it has a nice clean general answer. In one case, it might be
strong competition for resources. In another, it might be geographic
separation of a portion of a population from the rest. In some cases, it's
human intervention (i.e, domestication, etc.). In others, it might be
extra-powerful combinations of genes that resist being broken up and varied
during recombination. Going the other way, if the niche of a genetic
grouping is adjacent to similar but progressively differing niches, a
"species" may "flow" into those niches, changing as or after it flows,
resulting in further "speciation."
*Scientifically*, I don't think I *do* differ that much from Professor
Jones. It's just that, where he sees a problem, I see merely a misconception
as to the nature and function of concepts. He seems to see "species" as
requiring an out-in-the-world empirical distinguishing. I see it as mainly a
methodological tool, used for thinking and communication. "Okay, we say that
this is a species of primate. How does it relate to *that* species of
primate?" or, "For our purposes, we say that a species is distinct from
other species if their respective genetic groupings diverged some time ago
such that all or nearly all members of this grouping have a gene that no
member of that grouping has," etc.
Really Bad Epistemology (in this case, Platonism), leads to confusion and
false beliefs about the world, and to bad science. It's one of the chief
reasons why so many Christians don't understand evolution; they see species
as *metaphysically* distinct, instead of distinct by the accidents of
history and genetics and geography, etc. This Platonistic view is implicit
in Genesis, the Noah's Ark story, and in Christianity generally. They see
their *mental* distinctions as representing fixed, sturdy boundaries between
types of organisms. No wonder they have trouble with the idea of
"macroevolution."