Comments on: Species, not arbitrary, but not clear & distinct

By: Brian Schmidt

Brian Schmidt — Thu, 10 Feb 2011 08:25:55 +0000

#3 Bob: the legal definition of species under the ESA for vertebrates doesn’t match a biological definition. That doesn’t make the legal definition wrong: preserving the existence and genetic diversity of subspecies or even less-isolated subcategories has biological value, even if biologists might not like how “their” word is being used by lawyers.

In any event, it’s only for vertebrates, not for invertebrates or plants.

By: Lorenzo from Oz

Lorenzo from Oz — Thu, 10 Feb 2011 04:57:59 +0000

As biologist Joan Roughgarden puts it, Nature abhors a category. In a universe of multitudinous patterns and structures, working from fundamental particles upwards, our abstractions cannot be definitive "all the way down" but they can usefully pick up aspects of reality, provided we do not expect too much of them. (Which natural law theory generally does, for example. And racism really does.)

By: Chris T

Chris T — Tue, 08 Feb 2011 20:19:52 +0000

Even animals can get weird. What do we make of two animals that could potentially interbreed, but if left alone in the wild, would not?

By: Andrew Lancaster

Andrew Lancaster — Tue, 08 Feb 2011 19:13:27 +0000

I agree with others that you’ve balanced this well. I think a lot of people who think about this subject intelligently come down to having to balance pretty much the same fixed points you mention: a species is not normally just arbitrary; but then again there are reasons to say that species are not perfectly well defined. Thanks.

By: J. Wong

J. Wong — Tue, 08 Feb 2011 16:33:59 +0000

Just a note that Zeno’s Paradox is not a paradox at all. Zeno was trying to prove (by contradiction) that nothing moved. His paradox assumes that with a converging series in length you cannot have a converging series in time. This is clearly false: Both series must agree so for Zeno then the series in length was also not converging (i.e., infinite), and movement is an illusion. The reality of course is that both series converge, hence no paradox.

By: Markk

Markk — Tue, 08 Feb 2011 14:33:46 +0000

Look at Oak trees of various kinds in North America for a failure of the species idea to match up the genetics and morphology of “species”. It is a total smash. Gene frequencies do not match up well with what plants look like, and gene “transfer happens all over the “species” map and looks quite different to a morphological map.

By: bob sykes

bob sykes — Tue, 08 Feb 2011 13:18:21 +0000

Thanks for the reference to Hawkes and Coyne.

As a retired environmental engineer/scientist, I have long followed the debate about species. It is very confusing indeed. The classic Dobzhansky/Mayer definition (breeding population) works very well for animals. It is largely irrelevant for Bacteria/Archaea, which are mostly clones with occasional DNA transfer.

But what is most interesting is that conservationists, especially those engaged in species preservation, will have none of the Dobzhansky/Mayer definition. Instead, they rely entirely on morphology, and often trivial bits of morphology at that. E.g., the Florida panthers bent tail. This makes all sorts of decisions required by the Endangered Species Act to be unavoidably arbitrary and capricious. So much for science-based policy.

Most working biologists also depend on morphology over breeding, in large part because applying the Dobzhansky/Mayer theory to long-lived animals is all but impossible. Of course, if your studies cover a restricted geographic region, morphology is a very good species criterion.

By: Vincent Vizachero

Vincent Vizachero — Tue, 08 Feb 2011 12:48:36 +0000

Nicely done. I, too, liked the analogy to physicality.

By: Shecky R.

Shecky R. — Tue, 08 Feb 2011 10:42:09 +0000

I like the “physical objects” analogy. “Species” remains a mirage of a term for many. For that matter even “evolution” is a far more ambiguous, amorphous term than some would imply. Their lack of precision doesn’t take away from their scientific applicability, but it does lead to very prolonged, nuanced (and maybe unresolvable) debates/discussion.