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Wednesday, October 21, 2009

Ardipithecus, chimps, bonobos and christians

Martín Cagliari has uploaded
at his most interesting blog Mundo Neandertal, the full documentary of Discovery Channel on the Ardipithecus Ramidus. A must view (while the blog is in Spanish, the film is still only available in English).

I was watching it yesterday and is most educative, specially for the amateur with just a side interest in ancient hominins, as is my case. But, as always they have to outline a theory, a Christian-sounding one, of course.

So I was not too persuaded that the two most surprising features of aunt Ardi and her kin, the grasping but bipedal feet and the very short and blunt canines responded too well to the theory suggested at Discovery Channel. They argue that this means two things: bipedalism in forest area (this last ratified by botanical and zoological research of the sediments - excellent job with that too) and lack of the kind of male competition we see among chimps for group dominance and hence reproductive advantage (they talk about controlling females but it's in fact more as I describe it here, as chimps are polyamorous, even if in a hierarchical manner).

So far sounds good. But the hypothesis launched is that these new bipedal males with low aggresivity responded to a new kind of bond (couple) sort of reproductive economy, in which the males could go farther looking for "quality food" (whatever that means) and carry it on their backs sounded kind of implausible and too moralist to be real. I was not persuaded.

As it happens often checking with your pillow helps to clarify thoughts and when I woke up I came with fresh ideas: they had been all the time ignoring bonobos!

Bonobos have relatively large canines but are much more bipedal than chimps, ability that they use to carry things around or just to walk, either on ground or on branches (someone pointed out recently too that even gibbons, the most distant ape, are sort of arboreal bipedal animals, that arboreal bipedalism is not that rare among our kin). Bonobo males also do not compete for the females (so their canines may well be somewhat redundant) but that is not because they live in couples and males have any enhanced role looking for food in far away places but because they are even more polyamorous than chimpanzees but females tend to lead the groups up to a point.

And when you look at Ardi after considering the bonobos, she looks very much like one in fact, right? In fact it is then when she stops looking like some sort of ape-ish chimera and starts making sense. At least for me.

Bonobos are more closely related to chimpanzees than to us but they share with us some traits that chimpanzees do not: they have a clear sense of empathy and compassion and the females are sexually available all the time, not just when ovulating. This allows them to have much more cohesive and horizontal societies, where males do not need anymore to compete for females' favors.

As I said before, they are also more bipedal than regular chimpanzees. They look like a much better comparison than regular chimpanzees for our evolution, at least in many aspects.

So my hypothesis is that Ardi and her kin were to some extent like bonobos in the social aspect. What do you think?


Anonymous said...

Hominid gathering of food (abundant in the tropics) would be just as easy for females. Only hunting would produce a division of labour and hunting and that would only be necessary at high latitude where the only food in winter was 'on the hoof'.

As I understand it the highest ranking male chimp forces the females to mate with him (when they are most fertile), evidence for this is the injuries female chimps often have when they come back from mating with the top male.

Bonobos sex is not so caring as they do things adult humans get locked up for. Being perverse is a human characteristic?

Maju said...

Well, in Bonobos society Polanski would not be in jail, of course. The only taboo is that there is no sex with one's mother.
Guess that's what you mean and that they do empathize with others' pain, though they are pretty rude too.

But my point was not anyhow to idealize bonobos but rather that I saw a clear comparison between the evolutionary traits of Ardi's species (maybe our direct ancestors) and those of bonobos social behaviour. Bonobos have often been ignored in hominin comparatve studies and all the references are always coped by the more brutal cousin: the chimpanzee, what is an ideological choice. And very specially when these traits and even some fundamental elements of the hypothesis in the documentary (no heat cycle, or rather permanent heat) are easily comparable to bonobo reality.

Anonymous said...

Bonobos are the pygmy chimp, maybe there is an analogy with human pygmies who are said to be peaceful.

Maju said...

Well, bonobos are smaller and more slender than regular chimps but have diverged from them since at least 1.30 million years (MA) ago, very roughly the same dates as for the various fossil Homo species to have diverged.

We don't know if the Pan ancestor was closer to chimps or bonobos or something in between but only considering both we can get the idea. And Ardi does remind much more in several aspects to bonobos than to chimps. Hence my speculation that the common ancestor was in that bonobo/ardi range rather than in the human/chimp one. Within the most conservative approach, we'd need to at least consider both Pan species in equal terms and figure out the average.

It could be that Homo and bonobos have evolved in parallel towards achieving similar adaptations or it could be that the shared traits were ancestral to both branches to a great extent and that common chimpanzees' ones are actually the most succesful evolutionary trend in that branch, not for being more like humans but actually for having taken the evolutionary path more different to us, and winning the competition in terms of violence, where bonobos are obviously weaker. Bonobos are rather successful in their small niche but could not outcompete the warlike common chimpanzees most probably.

Luddhunter said...
This comment has been removed by a blog administrator.
Maju said...

The original post is not about creationists, whom I normally don't care about, but about evolutionist Christians, who are the one pretending that we evolved for a family.

Also I see that your link brings us to a download with a low WOT score (not apparently trustworthy) and you don't have any open profile no look like a regular poster so, precautionarily, I'm deleting your post, what looks like virus spam to me.

Sorry if it's an error.

terryt said...

"So my hypothesis is that Ardi and her kin were to some extent like bonobos in the social aspect. What do you think?"

You could ber onto something there. I seem to remember another blog claiming that knuckle-walking may have evolved from a more upright gait. If so bonobos would be more similar to the common ancestor than are chimpanzees. That would mean your comment, 'bonobos ... have diverged from them since at least 1.30 million years (MA) ago' should be reversed. It is the chimps who diverged.

Maju said...

Well, chimps and bonobos diverged from each other. Even if bonobos are more conservative, both did anyhow.

I also recall that theory on knuckle walking being derived. However this was based on orangutans and gibbons, who don't knuckle walk and instead often walk "upright" on branches (with the help of hands or not). But gorillas and both species of chimps have that trait on the other hand, even if bonobos use it somewhat less frequently, so it still looks dominant among our closest relatives.