Re: Specification for theories on human evolution
Phil Nicholls (pnich@globalone.net)
Sat, 18 Nov 1995 16:09:06 GMT
Paul Crowley <Paul@crowleyp.demon.co.uk> raged:
>In article <48ablb$sk1@geraldo.cc.utexas.edu>
> aduncan@mail.utexas.edu "Alex Duncan" writes:
>> >e11 The reasons for the development of bipedalism must be clearly shown.
>>
>> Can you explain exactly what it is you mean by "reasons"? Lots
>> of potential adaptive advantages for bipedalism have been offered, but
>> apparently they don't qualify as "reasons".
>It is my thesis that the adoption of bipedalism would have had
>enormous disadvantages (helpless infants, impeded mothers, no
>safe refuge in the trees at night, etc.) if adopted for any of
>the standard reasons. Here I block copy from a posting by Jim
>Moore quoting Phil Nichols in science.biology.evolution on 16 Oct:
> Pn> - when hands are need to carry food.
> Pn> - to obtain a better view of the surrounding area.
> Pn> - jumping across small brooks
> Pn> - treat displays.
> Pn> - when watching an unusual part of the surroundings
> Pn> - when locating another member of the group
> Pn> - greeting and courtship displays.
>I'm sure he meant "threat displays" not "treat displays" as you have
>pointed out elsewhere.
This was not given as a list of "standard reasons" for the origin of
bipedalism. It was given as a list of situations in which
chimpanzees engage in bipedal locomotion. This, in my opinion, is
the best place to start looking for the the origin of bipedalism.
Evolution works by modification of existing structures. The evolution
of behavior works by modification of existing behaviors. To treat
these as reasons for hominid bipedalism is a gross oversimplification.
>Consequently bipedalism must have been adopted for most particular
>reasons. These reasons can be identified to (IMO) a fair degree of
>probability with a little bit of thought.
>Here are some clues:
>The protohiminids can be thought of as being like modern chimps in
>morphology and behaviour.
No, that is a mistake.
>They were diurnal,
This is true of all anthropoid primates (with the single exception of
the Owl Monkey, a New World anthropoid)..
> omnivorous,
Generally true of many anthropoid primates.
>and had good social structure - so they could cope with diurnal predators.
Also true of all anthropoid primates and many diuranl prosimians.
>They actively explored a variety of habitats.
True of most anthropoid primates.
>Here's the important bit: they had recently acquired the same sort of tool-
>using capacity as now possessed by chimps.
Possibly. However, Gorilla's are not noted tool users in the wild (as
far as I know) and the only safe conclusion about a common ancestor
drawn from living apes would require the characteristic to be present
in all living apes and not present in monkeys.
>So what's the large food resource previously unexploitable by
>hominoids which they got at by using stones as tools (and I don't
>mean nuts).
>Anyone want to guess?
Bone marrow scavanged from carnivore kills.
Phil Nicholls pnich@globalone.net
"To ask a question you must first know most of the answer"
-Robert Sheckley
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