Mayr on "What is a Species"

[pierre deleporte]

A 12:22 27/04/2004 +0200, Zdenek Skala wrote:
>pierre:
>"The individuals potentially reproducing together are not really 
>reproducing with one
>another. They share a property (reproducing compatibility), which we use as
>a classificatory criterion. Such a species or population is a taxon, not a
>real network of effectively interbreeding  individuals."
>
>Zdenek: In fact, there is no "real network" in the nature that could be 
>observed - you can go to (some of) the individual interaction events and 
>will see that even these events are your "conceptualizations" without 
>ability to really observe the "process". Thus, the "real network of 
>effective interbreeding" is a mixture of some observations, some 
>hypotheses and some extrapolations - that is, again a "classificatory 
>criterion" quite similar to that used for biological species.  Not 
>surprisingly, population in this respect is also a class.
>Fuziness is important here - how much should be a population system 
>internally connected to call it "cohesive whole"? Is one inter-group 
>mating per generation sufficient? Or two? When we will come to the clear 
>result "this is not a whole but a class"?

I must agree with your realist view of what biologists are really doing !

Now, it seems to me that, as obviously as can be, a lot of members 
(individuals and "populations") of a "same species" have strictly no 
physical, let alone biological, connections or interactions. There is a 
continum of potentialities with more or less probabilities to be 
effectively expressed. You will not always find (or be aware of) a sharp 
discontinuity (e.g. the "significant typologic distance" making a useful 
new species, or the exact point of genetic isolation with no more back 
crossing). This should not lead anyone to such a loose definition of 
"individual" or "cohesive biological system" that anything potentially 
interacting would belong to the same "individual", even if chances of 
interaction come effectively down to zero. Which is, I think, what the 
proponents of "taxa-as-individuals" unfortunately do.

A question arises, which is not biological in itself but epistemological 
and psychological: why do some scientists try to force their classification 
(e.g. species) into a "real thing" (like "individual")?
I think they likely fear "not to be scientific" if they aknowledge that 
they are just classifying things on the basis of their self-forged 
criteria. I think this occurs because they are under influence of a flawed 
vision of what science is all about. They unnecessarily (and 
unrealistically) reject "scientifically useful classification (meaningful, 
relevant...)" outside "real science" or "serious science", which they 
should not do.

Science basically involves scientific explanation (like a phylogenetic 
explanation of life), and makes good use of classifications (at best, each 
one optimally designed for dealing with a specific question). Science is 
not reducible to "observations", experiments and tests. You can fail to 
"observe a species" and remain a scientifically pertinent phylogenetic 
taxonomist: your classification will make sense and be of practical use for 
evolutionary biologists.

We should not be shamed to class (that being the case, we better should 
stop being shamed just now).
We could be shamed only if we did not care of how-do-we-class and 
for-what-specific-purpose, altogether in a logically consistent way.

Best, Pierre.

Pierre Deleporte
CNRS UMR 6552 - Station Biologique de Paimpont
F-35380 Paimpont   FRANCE
Téléphone : 02 99 61 81 66
Télécopie : 02 99 61 81 88