Re: Dissecting the Aquatic Ape: Bipedalism

Leonard Timmons (
Wed, 31 Jul 1996 00:33:59 -0400

> Behavioral features can change much more quickly than phenotype.
> Behaviorally based speciation can take as little as 1000-2000 years.
> (Cichlids in Lake Nabunago, fruit flies in Hawaii.) Why this occurs is
> interesting, involving how learning and selection interact in defining an
> ESS. I have an old paper on the subject from back when I was doing ESS
> theory (1980-1990).

I can understand approx 90% of what you folks are talking about, so bear
with me. (ESS?)

My understanding is that hominid evolution was quite rapid as the
evolution of species go. However, I was unaware that the rapidity of that
change was a possible argument for it being behavorially caused. My
understanding of chimpanzees is that they have the rudiments of a culture
and that the culture can change from group to group. If our distant
ancestors had cultures too, isn't trying to predict the behavorial basis
of their speciation very, very, problematic?

If, however, we assume that hominid evolution occured as the result of some
learned behavior, then that event should probably be something that was
discovered accidentally and perpetuated through imiation and teaching. It
would have to become a part of the new culture. To me, the question of
bipedalism is a question of what changes in protohominid culture caused
bipedalism (and other structural changes that occured near this time) to
be a successful survival strategy.

In your answer, keep in mind that I know the meanings of a lot, but not all,
of the jargon that you use.

In line with this, I have been nursing a theory for a few years that I would
like someone to pass on. (This might be very amateurish, however.)

I have noted that among most species, when males fight they try to determine
one another's ability to inflict damage without actually doing so. I have
heard of the survival advantages to this strategy and thus the reason for
its evolution. However, when I look at us and our ancestors, I see animals
that are just about completely unarmed. We cannot really inflict damage on
one another of the same magnitude as one horned animal goring another. I
don't know why we lost our incisors, but the prevalance of alliances among our
ancestors may have eliminated even these (I guess).

One of the things that I noted in Ms. Goodall's book _In the Shadow of Man_,
is the difficulty that a group of chimps had in killing another individual
even when he was alone and outnumbered. The attacks were brutal, inefficient,
and prolonged. I remember thinking to myself, that I didn't remember reading
anywhere about the evolutionary consequences of two animals who fight, but
one is always killed and the other always unharmed (or only trivally so).
It seemed to me that the evolutionary consequences of such a situation would
be significant. In fact, I thought that such a situation must be somehow
unstable -- and that is why I had never heard it discussed.

To me, in order for this situation to exist, the two animals would have to
be nearly completely unable to harm one another. This seemed possible for
our ancestors in light of the accounts of the attacks above. However, at
some point our ancestors would have discovered how to quickly and efficiently
kill a rival and almost always remain unharmed. In my mind this would
cause a rapid spurt of evolution until the situation was corrected.

So I asked myself, "In what way could one protohumanoid learn to kill another
protohumanoid and be spared in the vast majority of cases?" My answer was
that this could be done by strangulation. This is a learned behavior and
can probably be taught to chimps today. It could easily be taught to others,
and the victor, if not severely bitten, would be essentially unharmed. To
avoid the bite would require stealth, which we already see in chimps and
would certainly be a part of the behavior of our ancestors.

What I like about this theory (and I admit that this is speculation) is that
in order to become good at strangulation the body plan of an ancestral ape
would have to change significantly to accomodate this behavior. If we assume
that the attacking ape was to the rear of the victim, in close contact, with
his arm around the neck, he would just have to hold on for four minutes or so
to be free of a rival. The successful attacker would be taller and able to
suspend his victim from the ground. The ultimate is probably being able to
stand up and lean backward and maintain balance while holding the victim above
the ground. Bipedalism may be a consequence of adapting to this requirement.
The loss of hair might also aid the attacker.

The successful victim would also require strucural changes to the head and
neck that would tend to defeat the strangulation attempt. Clearly a shorter
snout would be of some advantage. However, of even more advantage would be
the ability to call for help. With a restricted airway, the ability to
produce fricatives would be _very_ nice. It is my understanding that chimps
are, and maybe our predecessors were, unable to produce these sounds. No one
knows the basis for their evolution in humans.

In time, an entire culture might rise to enable one to survive person to
person combat more effectively. This would include wrestling matches, etc.
I mention this because, such combat in the form of wrestling is the oldest
form of sport. Stylized versions have evolved, though. It might even be
possible to assert that physical changes in humanoids were caused by
wrestling (or other person to person combat training) until recent times (HSS).

Anyway, since this is really (hopefully informed) speculation, I am just looking
for someone to tell me if this sequence has any major flaws in it. Or does it
hold together fairly well as an event that could cause the rise of mankind.