Re: Social evolution of hominids
1 Jan 1997 02:27:25 +0200

Sorry, I *couldn't* resist, after so many devoted discussions on
the topic in sci. newsgroups since Gould published his book!

Seriously, what I want to say is about sexual dimorphism of the
early hominids, expecially inside the male gender itself.

There was an interesting posting in about
orangs, which seem to have a kind of sexual dimorphism inside the
male gender. There are big males, which present the exaggerated male
phenotype, and other males, much more like the females, yet quite
fertile. The big 'top-males' inhabit their own revires, while the
other males roam around. It was said, too, that the bighorn, which
has a typical 'harem' society, presents a similar dimorphism. It is
only the top male, where the male phenotype is fully developed.

I wondered, had there been such dimorphism in the early hominids,
would the remains of the two male types be considered as two
different species? Only after a change to a more egalitarian system
such exceptional 'top-males' would not appear any more. wrote:

[of male dominance hierarchy]
> Great among gorillas, smaller among chimps, not so much among
> bonobos.

I thought something like that. The orang is more solitary than the
african species, so it's not a good example.

I believe that the change of the female sexual activity towards
more continuity had to do with the change of the social structure of
the hominids. After the female change, an extreme top-male hierarchy
was definitely no more possible, but the female behaviour hardly
initiated the change, however <g>. If it was that easy, we should
have more species going in the same direction. It may be, that the
female change was an adaptation to the new hierarchy, as well.
Instead of a single commander, there was now the whole bunch...

> Don't forget that bonobos (pygmy chimps) are continuously
> sexually active as well, and in all combinations (except,
> apparently, father-daughter combos). They seem to use it to
> defuse social tension. There doesn't seem to be any indication
> that the females don't enjoy it...,

I did not know, very interesting. What I knew about the sexual
behaviour of the african apes, was a film I once saw of chimps. There
was a female in heat with considerable swelling and restless
behaviour, typical for a dog in heat. I just extrapolated from the
top of my head, to be honest.

It seems that the 'top-male' hierarchy may have disappeared and the
continuous sexual activity of the females appeared at about the
level of the chimp-hominid branching, latest. No fear of dimorphic
males in australopithecines? Moderate dimorphism between males and
females? Big ones are all different species?

Prolonged, if not continuous, sexual activity is not unknown among
other species, where more or less permanent pairs are formed. Some
birds show it, for instance, and I heard that dolphins might have it
too, but I do not know if it is true. If it is, there are at least
three groups with the sociality-communication-intelligence complex
and 'false' matings, too. The latter may have to do with their young
being cared by both parents, or by the whole society including males.
Such young may need a protected learning period, which tells of a
relatively high level of intelligence.

All this boils to the conclusion that a certain bunch of
prerequisites was needed for our evolution. These prerequisites
appear in different combinations among some other groups, which may
have been on the way to a similar solution. We are not a unique and
improbable accident, just the most succesful of several parallell

As a keen supporter of comparative studies, I think this could be
a field for a nice little litterature referation for an undergraduate

Aila Korhonen in Finland