[wordup] On the evolution of cooking and the self-domestication

[Adam Shand]

This possibly the most fascinating thing I've ever read ... there's a 
bunch more to the article which is worth reading, I've only included 
one section below.

Adam.

From: http://www.edge.org/3rd_culture/wrangham/wrangham_print.html
Via: http://www.livejournal.com/users/jwz/343327.html

...<snip>...

There are two really fascinating things about human evolution that we 
have yet to really fully come to grips with. One is the evolution of 
cooking. Whenever cooking happened, it must have had absolutely 
monstrous effects on us, because cooking enormously increases the 
quality of the food we eat, and it enormously increases the range of 
food items that we can eat. We all know that food quality and food 
abundance are key variables in understanding animal ecology. But the 
amazing thing is that although at the moment there is no conventional 
wisdom that says when cooking evolved, social anthropology and all 
sorts of conventional wisdom say that humans are the animals that cook. 
We distinguish ourselves from the rest of the world because they eat 
raw stuff and we eat cooked stuff. The best anthropology can do at the 
moment is to say that maybe sometime around 250 or 300 thousand years 
ago cooking really got going, because there's archeological evidence of 
earth ovens.

This is fine, but long before earth ovens came along we must have 
learned to cook. And you would think that cooking would be associated 
with things like evidence in your body of the food being easier to 
digest, such as smaller teeth, or maybe a reduction in the size of the 
rib cage as the size of the stomach gets smaller, or maybe the jaw 
getting smaller. And there's only one time in human evolution that all 
that happens; that is, 1.9 million years ago with the evolution of the 
genus Homo. It's there we must look for evidence that cooking was 
adopted.

Once cooking happens, it completely changes the way the animal exploits 
its environment, because instead of moving from food patch to food 
patch, and eating as it goes, or eating in the food patches it finds, 
now for the first time it has to accumulate food, put it somewhere, and 
sit with it until it's cooked. It might take 20 minutes, it might take 
half an hour, it might take several hours. The effect is that all of a 
sudden there's a stealable food patch. Once you have a stealable food 
patch, that means that — life being what it is — somebody's going to 
come along and try to steal it. What this means is that you have to 
think about a producer/scrounger dynamic in which you've got 
individuals producing and individuals scrounging — and, horribly, 
females were the producers and males were the scroungers. Once you've 
got males bigger than females — fifty percent bigger by the time we're 
talking about, around two million years ago — then the effects on the 
social system would be large.

What we've got to think about is the idea that once you have females 
ready to make a meal by collecting food and cooking it, then they're 
vulnerable to having their food taken away by the scroungers — the big 
males — who find it easier not to go and collect food themselves or 
cook it, but just take it once it's ready. Therefore the females need 
protective bonds in order to protect themselves from thieving males, 
and this is the origin of human male-female relationships. The 
evolution of cooking is a huge topic that is virtually completely 
neglected. And whatever view you take about cooking, you have to say 
it's a problem that needs to be addressed.

The second problem is this: There is in a number of ways in the 
evolution of humans evidence of our behaving and looking as if we had 
the characteristics of a juvenile animal. For a hundred years or more 
people have talked about the idea that humans might be a pedomorphic 
species, a species that has juvenile characteristics in general, but 
this is too global a way to think about it. Still, it remains the case 
that much in our behavior, when compared with the behavior of our 
closest relatives, looks more playful and less aggressive when you're 
thinking about interactions at a social level within a group. We are 
also more sexual and more ready to learn, and these sorts of 
characteristics are characteristics generally associated with 
juvenility.

In a fascinating parallel, the bonobos — the second in the great pair 
of our two closest relatives — show all sorts of traits that are 
pedomorphic. We can see this throughout the head, where the morphology 
of the skull itself looks like the skull of an early adolescent or 
late-juvenile chimpanzee and much of its behavior looks juvenile-like. 
They are more playful, they're less sex-differentiated in all sorts of 
aspects of their behavior, they're more sexual, and so on. And we've 
yet to really come to grips with where this pedomorphic change has come 
from and what it means.

We've already got some wonderful examples of similar things occuring in 
other animals in the context of domestication. When we look at the 
differences between wolves and dogs, for example, we see amazing 
parallels to the differences between chimpanzees and bonobos. In each 
case for a given size of animal, you have the skull being reduced in 
size, and the components of the skull being reduced in size, including 
the jaws and teeth, and the skull looking more like the skull of a 
juvenile in the other form. The dog's skull looks like that of a 
juvenile wolf, and the bonobo's skull looks like that of a juvenile 
chimpanzee. And the behavior of each of them looks like it has strong 
components of the juvenile of the other species.

This leads to the thought that species can self-domesticate. There is 
good reason to think that over the course of evolution the bonobos 
evolved from a chimpanzee-like ancestor as a consequence of being in an 
environment where aggression was less beneficial to the aggressors, 
where there was a natural selection against aggression, and where 
selection favored individuals that were less aggressive. Over time, 
selection built on those slight variations in the timing of the arrival 
of the aggressive characteristics in the adult males. So it was 
constantly pushing back, favoring individuals that retained more 
juvenile-like behavior — and even juvenile-like heads — because that's 
what controls the behavior. Later, what you had was a species that had 
effectively been tamed, had been self-domesticated.

There is experimental evidence of this process. We have the Russian 
geneticist Belyaev, for example, who actually took wild foxes, selected 
for purely tame traits over 20 or 30 generations, and at the end of 
that time observed not only that the descendant foxes are as tame as 
dogs are nowadays — spontaneously — but also that they have a series of 
characteristics that have come along for the ride, incidental 
consequences that were not selected for but are just there. You have 
dramatic morphological ones, like the star mutation — the white spot on 
the forehead that you see in horses and cows and goats — that are just 
somehow associated genetically with tameness, and probably result from 
some kind of change in developmental events. There are also other 
morphological changes, like curly hair, short tails, and lopped ears, 
which happened in a number of domesticated animals, apparently because 
they've been selected for tameness. In addition, you get these smaller 
brains.

There is a remarkable thing about human evolution. We always tend to 
think that humans have just had a continuous surge in brain size over 
the last two million years, but actually over the last thirty thousand 
years brain size has decreased by 10 to 15 percent. The standard 
explanation for this is that we became more gracile at the same time — 
that we became thinner boned — which meant that we were lighter in body 
weight. And because there tends to be a correlation between body weight 
and brain weight, then maybe this explains our smaller brains. But I 
don't see any reason why brain size should be correlated with the 
amount of meat we carry on our bodies. This gracility is exactly the 
same pattern we see in the evolution of dogs from wolves, or bonobos 
from chimpanzees, or domesticated foxes from wild foxes. In all these 
cases an increasing gracility of the bone is an incidental effect.

I think that we have to start thinking about the idea that humans in 
the last 30, 40, or 50 thousand years have been domesticating 
ourselves. If we’re following the bonobo or dog pattern, we're moving 
toward a form of ourselves with more and more juvenile behavior. And 
the amazing thing once you start thinking in these terms is that you 
realize that we're still moving fast. Tooth size, for example, is 
extremely strongly genetically controlled and develops with little 
environmental influence, and is continuing to decline fast. I think 
that current evidence is that we're in the middle of an evolutionary 
event in which tooth size is falling, jaw size is falling, brain size 
is falling, and it's quite reasonable to imagine that we're continuing 
to tame ourselves. The way it's happening is the way it's probably 
happened since we became permanently settled in villages, 20 or 30 
thousand years ago, or before.

People who are anti-social, for example, have their breeding 
opportunities reduced. They may be executed, they may be imprisoned, or 
they may be punished so badly that they're kept out of the breeding 
pool. Just as there is selection for tameness in the domestication 
process of wild animals, or just as in bonobos there was a natural 
selection against aggressiveness, here there's a sort of social 
selection against excessively aggressive people within communities. 
This puts humans in a picture of now undergoing a process of becoming 
increasingly a peaceful form of a more aggressive ancestor.

...<snip>...