Re: Alex's gibbon-like CA

Phil Nicholls (
Mon, 13 Nov 1995 07:00:10 GMT

Paul Crowley <> graced us with the following

>In article <482psm$>
> "Benjamin H. Diebold" writes:

>> Paul Crowley ( wrote:
>> [snip]
>> : occurred. Environmental change would have had no bearing on such
>> : small groups. I'm sure that PA thought emphasises the climatic change
>> : largely because of a complete dearth of better ideas.
>> This seems an astonishing claim. Why on earth should you believe that
>> environmental change would have no bearing on small groups?

>You've lifted it quite out of context. Partly it was a reference
>to a discussion on the effects of major climatic change.

The quote is not a bit out of context. Most physical anthropologist
believe that the climatic changes that occurred in Africa played a
role in the origin of hominids. There are various ideas about how
this worked but most emphasize a shift from fine grain to patchy
resource distribution. Why would environmental change have no
bearing on a small group of protohominids?

>My point is that billions of species have been created.

No, billions of species have evolved.

> Only a very small proportion could be thought to be the result of major
> climatic change.

Why? This is certainly not what the fossil record shows. As a
matter of fact, it seems that major evolutionary events seem to follow
periods of mass extinction.

>Yet that explanation is always the first to be pulled out of the hat - in particular for
> hominid speciation.

It was not pulled out of a hat. It was pulled out of the data: data
concerning changes in African environments. It would really be nice
to see AAH'ers pull something from data but I suppose this is too much
to expect.

>So, in principle, we have to be suspicious whenever we see it.

We have to be suspicious when someone uses it and there is no evidence
for climatic change.

>Almost invariably it's a case of "Well, I can't think of anything else so it must have been the
>result of a change in climate".

Fact: Climate changed in Africa right about the same time as hominids
appeared. Climate change causes a change in the distribution of
environments, in this particular case an increase savannah-like

Fact: Early hominids exploited savannah-like biomes.

Gee, you think there might have been some connection here. Oh,
sorry, I forget that the AAH works best without facts.

>Secondly, I was referring to the period of hominid evolution when
>brains expanded and language developed.

No you weren't. You were talking about the hominid origins which we
identify with the appearance of bipedalism. Bipedalism was perfected
long before the brain expanded or language was developed.

> How many beneficialmutations did that involve? 10,000? Each of them had to spread
>throughout the whole population. So it had to be small and
>localized, or as I said: a lot of choke points. Major climatic
>change would have had no significant effect on this process. Even
>in the broadest sense, it is hard to see how any environmental
>change could have had a substantial influence.

It is very likely that increased brain size did not require 10,000
mutations. It may have required just a few -- those that regulate
the timing of developmental events. In any case what do you think
caused the "choke points" to occur? You know, you really should look
into a good book on evolutionary theory.


Phil Nicholls
"To ask a question you must first know most of the answer"
-Robert Sheckley