Re: tree-climbing hominids

Paul Crowley (
Tue, 10 Oct 95 15:39:26 GMT

In article <> "H. M. Hubey" writes:

> Paul Crowley <> writes:
> >I should have dealt with this last time. We are concerned with two forms
> >of locomotion: quadrupedal and bipedal. There is effectively no half-way
> >stage. (Obviously there must have been a transition, but it must have
> >taken place under very special circumstances - which is why the AAT
> >exists).
> Why does this have to be true. Suppose we plot x-pedalism along
> the abcissa and various measures of efficiency along the ordinate
> such as speed, carrying capability, efficiency or some combination
> thereof. If by 'no half-way stage' you mean that any one of the
> plots would have a dip in the middle (say zero quadped and 1 for
> biped) then all the talk revolves around this concept.

I really don't go for this mathematical stuff. Initially, it's a
question of design. You have to get the engineering right. There are
only so many ways you can design a bridge. There are only so many
ways that evolution can design locomotion into four-limbed mammals. If
I tell you to design a robot, you have similar problems. First of all
you need the specification: e.g. does it have to achieve any other
tasks? The chimp is a quadruped with adaptions for brachiation. The
specification for this putative tree-living hominid is missing - or has
never been drawn up. Maybe I am being dim in not being able to see a
design that is neither bipedal or quadrupedal, but I am not proposing
this "partially bipedal" creature; those who are suggesting that it
existed should describe it; having described it they should also go on
to say why evolution built it in that way - i.e. they should set out
the tasks that this design was meant to achieve.