Real Species

[pierre deleporte]

At 09:02 22/04/2004 +0200, Denis Brothers wrote :
>This, and a previous post of Pierre's, lead me to ask him:
>
>You obviously consider "species" to be epistemological constructs and not 
>to have any independent existence outside of our need to organise our 
>knowledge. However, you also stated that "speciation" is a process which 
>may lead to the fuzziness causing difficulties in our classfication. If 
>so, such processes must exist and operate outside our knowledge system, 
>and the entities involved in such processes must also exist independent of 
>our abilities to "classify" them.

Very, very nice point. I lately thought myself about this, and regretted to 
have used the word "speciation" when denying the observability of 
species... Which may legitimatley seem puzzling.
And the answer I made to myself is that there is no process of "speciation" 
properly: there is a process of evolution (processes in fact), but 
evolution has of course no "goal" and not even necessity of forming 
"species", anyway we conceive them. The process is one of mutation, genetic 
drift, selection... and it may occasionally result in what we call 
"species", i.e. a series of individuals, contemporaneous and not 
contemporaneous, fitting this or that series of conventional criteria.

Is this writing more consistent? I must remind this for later writing...

>Pierre also considers species not to be individual-like systems (like 
>populations) because their components are not all "really interacting". 
>However, paradigmatic individuals, like individual organisms, also do not 
>have components which are all "really interacting" at all times -

I mean at the same time, hence "observable" (see my answer to Curtis Clark)

>  the molecules and cells which make up an individual soon after birth or 
> hatching are diferent from those which comprise the same individual later 
> in life, and even the organs may be different.

Ignoring the delay in time is the trick used to present all molecules of an 
individual in its successive states, as well as all individuals of a "same" 
species, as a unique, observable "historical" individual. This does not hold.

>Even at any one time, can one say that there is any real "interaction" 
>between the toe nails and the fingernails, for example?

There is a fairly self-delineated physically connected and interacting 
network of cells. Cut away one of your toes and tell me some news (! this 
is a bad joke, please don't do that !).

Hence "contemporaneous" is as important as "spatially connected" for 
defining an individual, or a looser system. A real, observable one, not a 
human thought construct. Real things out there are contemporaneous and 
spatially related (to the list: please don't jump on Einstein's relativity. 
Of course I mean spatio-temporal connections as conceived by 
contemporaneous science).
See Richard Pyle's writings also about this notion of things existing by 
themselves independently of human thought.

>  Lineages are individual-like in similar ways, which is why some consider 
> it most useful to equate "species" with lineages, giving them a meaning 
> beyond our epistemological needs.

See my post to Curtis about cells - lifetime / individuals - speciestime. 
If you include your long gone feotal cells in your definition of yourself 
as an "individual", this individual is not an observable whole. Your 
"historical cohesion" is not observable, it is inferred, like a species' 
one (and that of any clade).

It's imaginable that one surveys the fate of an organism (or a population), 
and collects all dead cells (or individuals), and puts everything in some 
place and says: "ladies and gentlemen, this is the historical individual" 
(or "species-as individual"), come and observe it".

You try first, Denis...  ;-)    but we can certainly imagine the result: 
the "individual" will have a strange concrete appearence indeed. Isn't this 
mere consideration sufficient to do away with this misconception?

This is not to say that the species concept is stupid in itself. A species 
is not an individual, simply. It's a class of individuals. Doesn't this 
matter for "classification"?
If it's an individual, you just go out there and check for it. It is 
self-evident.
If it's a class, you have to argue as for your conventional criteria and 
their relevant context of meaningfulness. Harder job. But more realist 
conception of our science.

The latter point was: more about the bearing of philosophy on science (see 
Curtis).

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