Re: Alex's gibbon-like CA
Phil Nicholls (pnich@globalone.net)
Mon, 13 Nov 1995 16:21:39 GMT
Paul Crowley <Paul@crowleyp.demon.co.uk> graced us with the following
words:
>In article <48587j$84i@news.global1.net>
> pnich@globalone.net "Phil Nicholls" writes:
>> Paul Crowley <Paul@crowleyp.demon.co.uk> graced us with the following
>>
>> >There are two sorts of evolutionary change and this error confuses
>> >them: (a) where the species gets split by a geographical feature or
>> >environmental change and gradually drifts apart, as we see with
>> >chimps, gorillas and orangs within the last 2Myr; and (b) where a
>> >small group establishes a new ecological niche, for which it will
>> >need a relatively short period of isolation.
>> < snips >
>> In (a) abov, geographical isolation will alter the geographic range of
>> the species involved. Thus it is occupying a new niche.
>This is nonsense. As Mark Hubey has told you before: you are
>confusing habitat and niche. If the two species of chimps were put
>into the same bit of forest, they would most certainly *not* occupy
>different niches.
Not at all. Habitate is part of an organisms niche -- hence if you
change the habitate you change the niche.
If two species of chimpanzee were placed into the same bit of forest
they would HAVE to occupy different niches. If they attempt to occupy
the same niche then the competitive exclusion principle comes into
play.
In case you have forgotten, the competitive exclusion principle states
that if two species attempt to occupy the same niche they will compete
for limiting resources. There are three possible outcomes:
[1] One species will become extinct.
[2] One species will migrate
[3] One or both species will adapt in a way that avoides competition.
This is called niche partitioning.
>> Environmental change will also result in a new ecological niche. The
>> only difference between (a) and (b) then is that you are less specific
>> in (b) as to what aspects of the organisms niche is new and that the
>> size of the population is initally small.
>The most common occurence of (b) is when a small part of the population
>start to exploit a new source of food, e.g. a group of insects start on
>a new kind of plant. With a little bit of isolation that group will
>evolve into the new niche and soon become a new species. This is boring.
If a small part of the population begins to exploit a new food
resource (behavioral change) this will increase their fitness relative
to other members of the population (remember that each species is
composed of several populations).
>> >Do you also agree that climatic change (especially an adverse one) is
>> >unlikely to have been a factor?
>> No one said anything about "adverse" changes.
>The whole point of "forced" evolution is about adverse change. The
>forests thin out and the quasi-gibbons had to walk more. Remember?
[Sigh]
The reduction in forested areas didn't "force" protohominds to do
anything. They could have just stayed in the remaining forest and
habitat size would have acted as a limiting factor keeping population
sizes at a given level. However, as the forest shrinks and "thins
out" you get an expansion of this new biome and one population of
protohominids began to exploit that biome.
Exploiting a savannah biome requires terrestrial locomotion and if the
protohominids are predisposed to bipedalism when on the ground in a
manner similar to gibbons or spider monkeys then it makes sense that
they will become more proficient at it.
There is nothing adverse about the savannah -- just different.
>> It is unlikey that any major evolutionary change takes place in the
>> without environmental change.
>This is crazy. Where did *you* learn your evolutionary theory?
At the University of Illiniois and SUNY Albany. Recently by two
books: Evolution as Entrophy: Twoard a Unified Theory of Biology
(D.R. Brooks and E.O. Wiley) and Phylogeny, Ecology and Behavior: A
Research Program in Compartive Biology by D.R. Brooks and D.A.
McLennan.
>The first finches that got to the Galapagos benefitted from an environ-
>mental change(EC). Were the 13(?) other speciations also the result of
>EC?
The Galapogos islands have very different environments. Yes, they
did.
> Are all the billions of species the result of EC?
The pattern most often observed in the fossil record is one of
explosive growth in species diversity followed by decimation. Each
decimation is associated with major changes in climate. There have
been at least two massive extinctions in the earth's history -- maybe
three. Between the major mass extinctions there are smaller, less
drastic extinction events, each of which is associated with changes in
the environment. Change in the environment determines the tempo of
evolutionary change while previous evolutionary history determines the
direction of evolutionary change.
> OK, you can
>always go back a stage and find a change. You could always say that
>they are all the result of the Big Bang. (That was some EC!) But if
>you do that you are just into tautology. *Without* going back a
>stage, only a very small proportion of species arise from EC.
That is contrary to what the paleontological and paleoclimatological
evidence indicates.
>> >BTW I keep seeing the "evolution forces" error everywhere, and it
>> >drives me bananas. Today's UK Times has a report from Dr Charles
>> >Goodhart of Cambridge Univ stating the some h.s.s. were "forced"
>> >by climatic change to move south around 70kya. (It's only a news-
>> >paper report so I may be being unfair to him - but it is typical.)
>> >My point is that such change is slow in terms of a hominid lifetime.
>> >No h.s.s. packed his bags and said "Brrr, it's getting cold, let's
>> >go to Egypt this winter". It's a tempting scene, but it could not
>> >be more wrong.
>> Ahhh!!!!! Now I get it. Your a literalist! Think, Paul. 70,000
>> years ago. Europe. Ice Age. What do you think Dr. Goodhart might
>> have been referring to?
>Assuming Dr Goodhart's words were correctly reported, what sensible
>meaning could he have had? The Ice Age forced some individual
>hominids to physically move south? I'm at a loss for any other
>meaning. You tell me.
You can't live on top of an ice sheet, Paul. However, we are not
talking about a sudden migration here. It takes thousands of years
for glaciers to advance and human populations living in Europe
gradually migrated southward. If they were hunters then it is likely
they followed game southward but again this was a gradual process.
Phil Nicholls pnich@globalone.net
"To ask a question you must first know most of the answer"
-Robert Sheckley
|