> > Perhaps you would care to
> > clarify the situation by giving a definition that will stand up to
> > scientific scrutiny.
>
> 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.).
With respect, this is the point I was making.
> > 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.
I say again, this means, in my judgment, that there is no viable
scientific definition of "species".
> In a sense, you're right.
Thank you.
> 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.
With such a shifting meaning, "species" is distinctly un-useful as a
scientific term! It becomes like "evolution" - which has several
distinct meanings depending on the context. This is how debates get
confused and clear thinking is in short supply.
> 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.
This analogy is very much a darwinian interpretation of what a
"species" is. But it is not ging to help us resolve debates which
are questioning the validity of darwinism.
> 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.
Again, this is a darwinian perspective. What do you mean "not truly
separated"? Most darwinists appear to reason their way to this
position. From another perspective, one might say "there are
probably NOT a monstrously huge number of intermediate genetic paths
.. .. ". Analogies are fine as long as people realise that they are
only analogies to help people understand concepts. But if you
present this analogy with the claim that this represents the truth
about living things, you are not doing science a service.
> 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.
The adaptive landscape is a good darwinian analogy, no more.
Non-darwinians, whether they be Basic Type biologists or Punctuated
Equilibria palaeontologists will dissent from it. If we are seeking
to encourage science, we will encourage debate and start asking
questions about how we can test between different concepts of what
species are.
> *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.
Yet the way you have presented it suggests to me that it can result
in confusion and miscommunication, because people are bringing
different content to the same word.
> "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.
I am aware that some want to define species using genetic
information. They have not resolved the controversy. Steve Jones is
a geneticist - and he ought to know something about this!
> 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."
I have no intention of defending Platonism. It provides a framework
for interpreting data, just as darwinism does. To progress in
science, we need to be able to see how our conceptual frameworks
influence our thinking about the interpretation of data. I have
sought to point out above how darwinism has this subtle effect. What
many darwinists seem content to do is to develop their position by
force of logic: "the world must be like this because these are the
rules of biology". The scientific approach IMO identifies the
different approaches and seeks out ways of testing alternatives.
Darwinism has singularly failed to do this, and I look forward to the
day when this situation changes.
Best regards,
David J. Tyler.