Re: Becoming altricial/bipedal

Paul Crowley (
Tue, 10 Oct 95 12:55:25 GMT

In article <45b7bb$> "Thomas Clarke" writes:

> I wonder though why you think it is significant that
> " There is no need to rely on
> geological events for the separation or expansion of the species."
> There were sea level fluctuations that turned highlands into
> islands during the correct time period, so the events need not
> be "invented". Speciation is much easier on islands as Darwin
> observed.

Very few other species are created in this way. Newly created islands
have ecological niches which can be filled and those on the Galapagos
were filled by a speciating finch which happened to get there. Danakil
presumably did not have unfilled niches. Secondly, I feel that it's
too small for a viable species to exist for about a million years.
There would be too much else going on during that time. The species
would be unlikely to both survive and remain separate. Thirdly,
I've seen no good account as to why the hominoids there should have
developed differently from those on the mainland; slight differences
would emerge - but a new species with a radically new form of
locomotion? Fourthly, to say that the flooding of the Sea of Afar
was crucial is to say that if it had not happened the species would not
have developed. To rely so heavily on such a chance, geological event
in such a unique geography is just too much. Fifthly, I believe that
the Danakil scenario is a case of the common "evolution forces" error
on which Jim Moore and myself were commenting recently.

I've set out a list of criteria for creation of a new hominid species
in the "tree-climbing hominid" thread - as a challenge to Alex Duncan.
I do not believe that he's going to be able to meet it. But I want to
give him a bit of time. It's important to get the criteria right first
and he may want to question or modify or add to them. Please put your
ideas in too.

As soon as we see that the Savanna/Mosaic scenario cannot provide a
remotely reasonable hypothesis, I'll set out a "new improved" AAT
which, I believe, will satisfy every one of the (revised?) criteria.