Re: Crowley theory

David Froehlich (
Sun, 15 Oct 1995 16:01:56 -0500

On Sat, 14 Oct 1995, Paul Crowley wrote:

> > > I presume you accept that there were major disadvantages in becoming
> > > bipedal: i.e. the mother had to use one or both arms to carry her
> > > child everywhere she went, meaning that she could not run, climb,
> > > use a club, or throw rocks when in the presence of a predator, nor
> > > could she sleep in a tree at night. In fact the viability of her
> > > existence is questionable.
> >
> > I accept nothing of the kind.
> All I'm asking about is the disadvantages of *becoming* bipedal. This
> happened. So it had some advantages (we would disagree about what
> they were - but we are not discussing that). Please answer:
> (a) Did this process also have disadvantages?
> (b) If so, would they include those I mentioned above?

A) it is possible that there were disadvantages.
B) Yes those you metioned -could- be some of them, however, we have no
evidence that they were. I am not disagreeing that your contention could
be true, that bipedality was very difficult to evolve, where you and I
disagree is that you are a proponent and I am a skeptic. I (as a
reasonably intelligent scientist) am your audience, and I am saying that
you are assuming that these disadvantages make terrestrial bipedality
impossible and that only leaves aquatic bipedality (sensu AAS) as the
option. Now, I will admit that I am biased against AAS, yet I still find
the basic premises untestable. How do you know that maternal
survivorship is decreased. Your basic statement is "it must have
decreased because I can see no way for these females to be both bipedal
and rear offspring" I challanged this basic contention. How would you
test this premise. If I do not accept your premise, I will not accept
your conclusion.

> > Any primate mother has disadvantages when
> > rearing offspring, but they seem to get along quite fine? How do they do
> > this? There are a variety of responses including parental investment
> > either in terms of protection or food sharing. Why are these not an
> > option? Especially since all hominoids live in comunal groups.
> You are just ducking the issue here. You are saying that all sorts
> of responses are possible. Responses to what?

Responses to having to care for a helpless infant. I am making a counter
claim to your contention. Basically that other organisms rear their
young without apparent decrease in survivorship (e.g. babboons, vervets,
gibbons, etc.) they do this through a variety of behavoiral and physical
ways. Why are the proto-hominids incapable of similar responses.

> > You still have not addressed my basic question of how you would know if
> > any of the asumptions are wrong?
> I just don't understand your point. Would you mind listing the
> assumptions that I appear to be making, to which the question
> "how would I know if it was wrong?" could properly be addressed.

You should be aware of your own assumptions, because anything that you
assume is untestable and lost from your analysis. If I want to study the
relationships of higher primates, I cannot assume without any evidence
things like hominid, catarhine or platyrhine monophyly since this is what
I want to discover. Likewise, you cannot assume without evidence that
bipedality is imposible to achieve in a terrestrial setting if that is
what you want to test. (I realize that the two examples above are not
specifically what you are asking, but they demonstrate my point).

I am just an interested party to this discussion and what I am doing here
is tossing rocks at your theory. I do not want to do your analysis, I
have my own interests, however, what I can do is point out the weaknesses
in your methodology.

Hope this answers your questions. (we will probably never totally agree
but what I would like to see is a more robust version of your line of

David J. Froehlich Phone: 512-471-6088
Vertebrate Paleontology Laboratory Fax: 512-471-5973
J.J. Pickle Research Campus
The University of Texas, Austin, Texas 78712