Re: Social evolution of hominids (long)
11 Jan 1997 07:56:20 +0200 wrote:
> Comparing orangs, gorillas, chimps and bonobos isn't particularly usef
> since we have very little evidence of social behaviors of protohominid
> and the common ancestor of humans and apes.
> The degree of sexual dimorphism between a human male and a human femal
> would at least suggest that differences in size between the sexes nowh
> near approaches that of modern apes such as the orang and gorilla. Wha
> would this suggest to you?

This is a hypothetical succession of events, based on what I know :

1 At the level of the *common ancestor* of all apes and hominids the
social structure was what the gorillas have today : a very big
dominant male with his group inhabiting a moderate sized area in
deep forest.

2 The *orang* moved to east, and for some reason, only the dominant
males stayed big and territorial, the females and younger males
wandering around. The females still prefer the big males. Maybe
there is not food enough for the foraging of complete groups.

3 The climate turned more arid in Africa, and the local form began
to cleave. Where the climate did not change, like in the rain forests
of the mountains and somewhere else, the apes went on as before. The
*gorilla* has been continuously there.

4 The ancestor of *chimps* found itself in a less dense forest than
before. There were more big predators, more cooperation of the males
was needed, and the order of the male hierarchy had to become less
steep. The large difference between males and females became a bit

5 Part of the ancestral form, however, happened to live in areas
where drying did not stop to that. They had to dare to the open
to reach isolated forest patches. Now it was not enough that the
males were cooperative. In the open, pregnant and lactating
females were in danger, and they had to be protected by the males.
Yes, their receptive period was prolonged, and they had sex with
all males of the group. Every male was ready to save any female,
because she was his sex partner and could well bear his own progeny.
This was, of course, an inborn reaction to a mating partner.

This is exactly, what is happening to the bonobos today. I know of
them what I have seen written in the 'net. This is: they live in a
more open area than chimps and they are promiscuous. I bet that
their area has dried after the Ice Age and they begin to adapt to
that change.

Dolphins have a similar situation. They move freely in the open,
their females bear big young and nurse them for a long time, so
the females are permanently receptive and have sex with all males
of the group to get help from the nearest members when needed.

Why did our ancestral form become bipedal? Because the female could
not use her hands for support, when fleeing a presumptive leopard
with a baby, while the males tried to hinder the cat. She had to rush
a distance, and bipedally, I think, could be the strategy even
of a chimp, or am I wrong? The best runners were the mothers of the
next generation. (No, I am *not* a hard core feminist, but the logics
seems to go like this all the time.)

This is where the human altruism originates, too. It is definitely an
inborn behaviour, with great rewarding feelings after helping and
strong punishing feelings if you don't. You get extremely frustrated
if you can not help. You may explain yourself, how fool it is to
help, and yet you help. That means, that altruistic behaviour must be
very old, and have had crucial importance at some stage.

The members of a small group of these early prehominids, in an
evironment where they still had difficulties to get on, desperately
needed each other. A lone individual would be gone after a few
nights. Very great investment in any group member was good
evolutionary strategy, like fixing a hole in a dam.

Bonobos? I dont' know, but I bet that some initiative form of
altruistic behaviour must be present, compared to the chimps, at

Dolphins are commonly known to help any member of their group, and
even of other groups, supporting them on the surface for hours. As a
whole, they are a nice parallell in a very distant environment.

Now we have left the apes and have an early, promiscuous, altruistic
and bipedal-directed *hominid*. What followed? Not much, for a long,
long time, in the sense of social evolution.

6 The human line appears in sight in flesh and blood in the !kung
san. Full humans, definitely our species, but still retaining the
ancient promiscuous social structure. They have been pushed to the
edge and probably still need group cooperation more than any other
people. There may be other people who have retained such strategy,
but anthropologists seem to have difficulties in presenting these

7 The main part of our species has left open promiscuity, and
tries to stick to pair forming with varying success. Life-long
pairing is largely a cultural trait, for there is no inborn
mechanism supporting it, similar to the altruistic reflex. We have
just 'falling in love', a prolonged remnant from what originally was
mere mating behaviour, and it is not near that old or it would be
more long-lasting.

Why do most cultures favour permanent pairs? Probably because such
cultures have survived. But before such cultures could appear, life
had to become easier, so that the group was no more crucial for
survival. New tools and methods, maybe better climate.

How old are the pair-favouring cultures? From before the pair-
favoring hunter-gatherers radiated? But there are remnants from
maternal societies around the world, mainly primitive
agriculturalists, among paternal hunter-gatherers. Did all these
evolve independently from a preceding promiscuous base? It could
be so. Then pair-favouring could be a much younger trait than we
do think.

> Susan
> --

Aila Korhonen in Finland