Re: Alex's gibbon-like CA

Paul Crowley (
Fri, 10 Nov 95 21:36:47 GMT

In article <47t3n1$> "Alex Duncan" writes:

> Nonetheless, when large-scale climatic
> changes happen to coincide with numerous speciation events (as has been
> demonstrated for the African Neogene), it is tempting to speculate that
> significant evolutionary change and change in habitat are somehow
> correlated.

IMO the source of the temptation rests on a common error, probably
derived from human experience - "there were adverse circumstances
so we adapted to cope with them".

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.

I think that we are agreed that hominid speciation resulted from
the second mechanism. Do you also agree that climatic change
(especially an adverse one) is unlikely to have been a factor?

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.

There is supposed to be very rapid global warming happening now.
Have you heard of any mass movements of any species being "forced"
north? Yet this is how it's imagined in the African Neogene!