Chimps

Hi everyone!  Before I write anything, I'd like to remind you all that I wasn't in class last week, so the opinions on this post are formed entirely from two Wikipedia articles, posted below, as well as this article which suggests that human evolution had everything to do with getting out of the forests and into the grasslands. I've carefully not read anyone else's blogs before posting this, though I look forward to hearing your thoughts. Thanks!

So, in thinking about why humans and chimps might have diverged, I looked into how chimps and bonobos seem to have diverged to see what we might learn from that mechanism.  Wikipedia says that they might have been split apart by a river suddenly splitting their habitat; neither species can swim.  The ecology is not the same on the two sides of the river, and the way the two species have adapted to their unique surroundings is quite informative.

Chimpanzee social structure is based around a heavy meat diet, which means that on a basic level the community must be organized to go on hunts, a highly organized, relatively difficult, and periodic activity.  This gives rise to a strictly hierarchical structure with lots of aggression, because that structure allows for orders to be passed down and followed efficiently and with no dissent.   

Bonobos, by contrast, survive mostly on fruit, with termites, small animals, and leaves supplementing the diet. This means that their basic food-getting activities are more constant than periodic, easier, and dependent on food that is thinly distributed rather than walking around as huge, discrete chunks of meat.  In this environment, the primary social challenges have to do with distribution, both of the bonobos themselves and of the food once they gather it. In simple terms, they have to make sure everyone gets enough, and that there are never so many bonobos in one place that they drill a hole through the food network (trees, termite nests, etc.).  They solve these problems with the famously ubiquitous bonobo sexuality as a conflict mediator so that no one fights over food too much, and with free female migration between troops (see article) to keep everyone spread out.

Both species use tools appropriate to their food sources.

So, with this example in mind, what might have motivated humans to employ our own, third speciation? I'm going to take the forest vs. grassland thing and just run with it, here, even though I haven't looked deeply into what was really happening in Africa at the time.

The challenges of the plains initially resemble those of the chimpanzees' environment, in that before agriculture (waaaaaay before!) most of the food on the plains was running around rather than growing.  However, no matter how much we might have turned up the aggression in our social networks, walking monkeys are just not set up to compete for eating ungulates with, say, cats.  We were the new kids, and could not continue to do things in the old way, even the plains' old way.  For our solution, I like the scavenger theory.  Persistence hunting aside, scavenging is a lot like gathering, and makes excellent use of our touted bipedal efficiency (that is, we can wander around all day looking for something dead).  In this sense, waiting for the grazing animals to fall over on their own before we ate them would have been a good fit.

So, that's a niche.  But there was already a scavenger community in the plains, from vicious dogs to birds!  We can't fly and we're not dogs, so we needed to find a sub-niche.  Isolated from all our forest advantages,  we were down to tool-making.  It's all we had that would translate seamlessly into our new environment, because it's even easier to change than behavior is, and even more versatile because it happens outside the body.  Making increasingly fine and powerful tools would have let us compete in one small, sub-sub-area of plains-style survival, and finally given us something that we were better at than anyone else: butchery.  Scavengers are generally set up to eat one particular part of a dead animal, and are stuck with bodies that are perfectly tuned to eat that part, down to sense organs that allow them to find the corpse at the proper stage of decay.  With tools, we could vary our target areas as much as we wanted depending on when we found the animal and who had found it first, as well as getting to things that barely anyone else could, like bone marrow.

Once we found such a cozy niche, we would have survived and run with it, giving us the time to move from tools to weapons, allowing us to take care of the competition not by out-competing them but by simply finding and killing them wherever we were.  This would fit the general trend of human behavior both at the time and since then, as well as explaining the advent of primitive, but very effective hunting methods in Africa. That is to say that persistence hunting would have been more worthwhile once we figured out how to kill lions, for example.

So, here's the articles about chimps and bonobos:

http://en.wikipedia.org/wiki/Chimpanzee

http://en.wikipedia.org/wiki/Bonobo


That's it! Can't wait to see what you guys think.