john_SPAM{at}wilkins.id.au (John Wilkins) wrote in
news:c5ib3h$1mvh$1{at}darwin.ediacara.org: 

> Tim Tyler  wrote:

>> I have no objection to giving terms solid meanings.
 
>> However I don't think it would be wise to *define* the properies of a
>> species to necessarily exclude all the properties of its members.
 
> There is a logical fallacy known as the fallacy of composition - that
> the aggregate shares the properties of its parts. If I have a digit
> that is 6" long, do I as the aggregate that includes that digit have
> the property of being 6" long? No. It pays to consider the difference.
 
Well, OK, but what about the differences between marsupials and 
placentals? The difference includes body temperature in addition to the 
difference in reproductive mode. Now in terms of niche specialization, we 
see all sorts of marsupial  species showing convergence with placental 
species - but in almost every case where placental species came into 
competition with placental species, the placentals won. From a certain 
standpoint, you can say they won because individual placentals 
outcompeted individual marsupials. From the standpoint of understanding 
the geographic distribution of species, they won because of differences 
at a much higher level than the individual.     

>> "Consisting of red organisms" *should* be permitted as a property
>> of a species.  Forbidding it on the grounds that it is the organisms
>> (and not the species) that is red would be playing a pointless
>> semantic game, and - IMO - it would lead to much easily-avoidable 
>> confusion.
 
> No, there are two properties in play:
 
> of the organisms - "is red"
 
> of the species - "consists of red organisms"
 
> "Is red"  "consists of red organisms"

Of a kangaroo:

consists of molecules with an average temperature of 36 degrees C

Of a kangaroo species:

consists of molecules with an average temperature of 36 degrees C

Of marsupials:

consists of molecules with an average temperature of 36 degrees C



>> I can see it might be useful to want to distinguish between emergent 
>> properties of species, and those that they inherit in an additive
>> fashion from their members - but I *don't* think the desire to make
>> this distinction can justify bending the whole concept of
>> "species selection" out of shape.
 
> Don't get me started on emergence. It is, IMNSHO, a different way of
> saying "we can't calculate it ahead of time", that's all. It has no
> ontological implications, only epistemic ones.

I was always bad at resisting an intellectual challenge :-) But 
forgetting about whether we can calculate properties ahead of time or 
whether that implies anything about the properties, there are properties 
of species that appear at the species (or at least population) level. For 
instance, the reproductive rate of rats decreases with increasing 
density. At an individual level this causes the reproductive rate to vary 
significantly with density, while at the level of the population it 
causes the reproductive rate to be relatively constant despite changes in 
density. This species level property of rats has been implicated in the 
ubiquity of rats on small islands.


Flocking is another example. Passenger pigeons became extinct even though 
there was still a rather large population present when hunting pressure 
eased. For each individual bird during their heyday, the flocking 
behavior was adaptive. Once the population was reduced, the behavior was 
no longer adaptive - but only _because_ of the reduction in overall 
population. Is this individual selection? Well, in one sense, yes - 
however it may be better understood with reference to the species.The 
behavior pattern could not emerge until the pigeons became numerous, and 
it did not become non-adaptive until the pigeon population was decimated.


 
>> *Everyone* agrees that species selection in biology should refer to
>> differential reproductive success of species - i.e. on selection
>> "choosing" species on the basis of differences between them.
>> 
>> The sole point of contention is whether things like;
>> 
>> * "consisting of large organisms"
>> 
>> ...and...
>> 
>> * "consisting of winged organisms";
>> 
>> ...should be permitted as properties of species which are eligible
>> for being used to distinguish between them.
> 
> Logically, yes, they can. That is why I said above it is logically
> possible. But "consisting of winged organisms" has to have an
> *economic* differential value for the *species* to be selected (or any
> supraorganismal entity). Otherwise the species merely inherits the
> selective values of the organisms, and there is no species *selection*
> going on here, just sorting.

It has been argued that one of the things that did the dinosaurs in after 
the comet hit might have been that sex of dinosaurs was still based on 
incubation temperature, as it is in crocodilians. So after the fall there 
were too many males - this should also have been true in humans, unless 
Cain and Abel had an unrecorded sister :-) Now are you going to argue 
that this is simply sorting? At some point the distinction loses value, 
because it fails to distinguish between characteristics - e.g.large 
populations of small individuals - that are typical of many species 
across many taxa, and characteristics - e.g. turtles having a carapace - 
that are typical of only a single order. That order includes  dominant 
species in most freshwater ponds, but in few other ecosystems. How is 
this phenomenon best understood? The particulars of the species changes 
from pond to pond, but they are all turtles. 

Yours,

Bill Morse
---
þ RIMEGate(tm)/RGXPost V1.14 at BBSWORLD * Info{at}bbsworld.com

---
 * RIMEGate(tm)V10.2áÿ* RelayNet(tm) NNTP Gateway * MoonDog BBS
 * RgateImp.MoonDog.BBS at 4/28/04 5:41:44 PM