Got milk (alleles)?

As you probably know, everyone should drink milk. Lots and lots and lots of milk. All your life. Or so says the American Dairy Industry, often using those sexy posters of famous people with milk smeared on their faces.

The truly amazing thing about those posters is that the people in them more often than not seem to have an ethnic identity that I, as a trained Biological Anthropologist (and thus keeper of this sort of knowledge) can easily see contraindicates milk consumption. Most of these individuals would likely be unable to break down the lactose in the milk because they have the “wild type” or “normal” allele that facilitates the shutdown of lactase production some time in early life.

Now let’s be clear about this. We humans are mammals, and as mammals, we drink mother’s milk while young. This is facilitated by the production of lactase, an enzyme that breaks down the main energy bearing molecule in milk, the sugar lactose. But your basic well adapted mammals should not bother producing the enzyme lactase after weaning normally occurs … maybe a few years after in a long-lived mammal like humans … because it is inefficient and potentially risky to produce enzymes you don’t need.

Why is it inefficient? Well, there are thousands and thousands of enzymes and if we just produced all of them all the time in all our cells, that would be really costly of raw materials and energy, both of which are required to produce them. So, evolution has shaped, via the brilliant designer of Natural Selection, our multicellular bodies to produce enzymes only in the cells they are needed in (from which they may be exuded on occasion, as is the case with lactase, a digestive enzyme). This is much more efficient. By extension, the system should be (and usually is) selected to produce specific enzymes when they are needed instead of all the time from birth to death. By doing this we save a lot of raw materials and energy.

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The Evolution of Human Diet

Chimp, Australopith and
Human Teeth Compared.

The evolution of human diet followed a major zig (as in zig-zag) in a wholly unexpected direction, followed by the most significant biological innovation to ever occur among multi celled animals: The invention of cooking. I’m actually going to point you to two papers on this topic, and provide a brief summary of the ideas here.

Let’s start with the bold assumption that humans evolved from a chimpanzee-like animal. This is tantamount to saying that the last common ancestor of chimpanzees and humans was, essentially, pretty much like a chimpanzee. At another time, I’ll write a post on why this is a good assumption, but for now lets just go with it. Some large percentage of human evolution experts like this assumption, a bunch of others hate it (which is the usual pattern for most ideas in human evolution).

A mammal’s diet is reflected in physiological attributes that can be discerned from the fossil record. Body size, the nature of the teeth and associated muscles, possibly the shape of the mouth’s cavity, and even the overall size and shape of the gut may be closely connected with diet.

If we draw a direct line from a presumed chimpanzee-like ancestor to modern humans, Continue reading

Man the Hunter

I’ve never been that big of a fan of hunting as the explanation for everything that happened in human evolution, and I’ve tended to explore other areas more. This has led some to believe that I’m simply against acknowledging any role of hunting in human prehistory and evolution. This of course is not true at all, but I do think the issue needs to be addressed in a more complex and subtle way than it usually is. The present comments are a tiny contribution towards a much larger requirement of thought and discussion.

Why is hunting thought to be a key factor in human evolution? Partly because it was once widely believed that among the primates, only humans ate a fair amount of meat (not counting insects). If human hunting and meat consumption was unique among primates, then the evolution and effects of this behavior could easily be understood as vitally important. Moreover, a lot of fieldwork and thinking about human evolution centered on Europe, where cave paintings of animals were common, with some hunting themes seemingly represented in these paintings.

Of course, the uniqueness of human hunting behavior is now understood to be a gross overstatement. There is hunting of mammals and the like by several primates, and in particular, chimpanzee hunting (mainly of monkeys) is fairly common.

We now know that almost all of the important events that have happened in human evolution (since the chimp-human split) happened in Africa, and that the European record, while interesting, is not the primary record for these events. Therefore, one would think that the European bias would be somewhat reduced in current thinking (the fact that it is not is of great interest, but I’ll not go into that here!).

But I think the most important reason for hunting taking center stage in the study of human evolution, to what appears to be an unjustified level, has to do with the nature of “Man” and the nature of “Hunting.”

Have you ever been hunting, or been along with others while they did so? I’ve accompanied both North American game hunters (armed with firearms) and Efe foragers (armed with arrows and spears). Most of my time has been in the latter pursuit, and in a few instances, I joined the hunt not just as an observer but as a participant/observer.

I don’t think hunting is a normal human activity in the same way that hunting is a normal lion activity, or a normal wolf activity. Humans seem to react to hunting in a very powerful way, similar to how humans react to violence in general (and hunting seems to be fairly violent) or to certain kinds of sporting events (as observer or as participant). A lot of yelling and screaming and jumping around can ensue under certain conditions. Yes, most forager groups disdain bragging and avoid giving too much credit to any individual for being a great hunter, but the visceral reaction to, say, a near miss or to those moments when the hunted animal turns on the hunter (usually only briefly and to the animal’s final chagrin), is powerful and can’t be covered up or put into the background by cultural norms of modesty.

Richard Wrangham thinks that it is possible that hunting by chimpanzees is more important as a form of male bonding than it is as a form of food acquisition. He bases this assertion on two things. First, the chimpanzees at Kibale, where he works, seem to hunt more when there is abundant non-meat food (i.e., fruit). Hunting is not used by these chimps as a way to supplement their diets. Hunting is not part of a sensible ecological strategy for garnering energy from the environment, but rather something that is done when one has the extra time and energy. The second part of his argument (as I understand it) is that one of the most critically important things a male chimpanzee can do, in evolutionary/fitness terms, is to be adept at cooperating with other males of it’s group, to facilitate the act of killing extra-group chimpanzees. The experience of hunting monkeys and the male-male interaction that relates to this primes and prepares the chimps for this important yet rare event. Hunting monkeys is training for being an effective, fierce, demonic male chimp.

Is this the case in humans? There is no way to know this at this time. There certainly are groups of human foragers (in the ethnographic present) who rely so much on meat that hunting is basically a form of subsistence, no matter what other function it may have. Even when plant foods are abundant, meat is still important to almost every group of forager (and non-forager, likely) as a source of “complete proteins.” All traditional human hunting is imbued with ritual and ceremony that exceeds that generally linked with gathering. So in the end, there is evidence that hunting can be and often is an ecologically important activity for human foragers. There is also evidence that hunting is (probably) always an important social activity, mainly among men.

[Ask me later: Why a photograph of the Afrikaans Language Monument in this particular place, at this particular time…]

So, now, return to the idea that the “man the hunter” concept is something that derives from the nature of “Man” and the nature of “Hunting.” As you may have guessed, I’m not using the incorrect gender non-neutral term “Man” to refer to humans. I’m talking about men. Guys, to be more exact. Guys, for various reasons including insecurity about reproduction as well as food and subsistence, etc., tend to invent methods of bonding that can sometimes be quite elaborate. In many societies, throughout time, hunting has probably been one of these methods. Certainly, many of the male scholars who first looked into human evolution were themselves hunters (shooting quail on the moorland, big game in East Africa, etc.) and had a good, Victorian understanding of this process of bonding.

When a 19th or 20th century guy archaeologist holds a beautifully made, often phallic-shaped obsidian spearhead in his hands, feeling it’s heft and running his fingers along the still sharp, elongated, stone-hard edge, he is bonding with another guy, of a much earlier time period, who could probably have killed his quarry just as effectively with a sharp stick, but opted instead to produce, carry around, display, and use this really cool piece of gear. So it’s a guy thing, and it’s a gear thing. It’s sort of a guys-with-gear thing.

Hunting isn’t likely the driving force in human evolutionary change, but it can certainly be an important human activity that is related to human evolutionary change.

One final brief note on something to be addressed at another time: The assumption that hunting by men is central to human evolution has led many to assume that hunting drove the evolution of tool use, and thus, tool use is a male thing. This contradicts the best evidence we have about technology in primates, which suggests that females, not males, are the tool makers, tool users, and the teachers (or at least facilitaters) who pass this ability on to subsequent generations. So, gear, it turns out, may be more of a girl thing after all.

Evolution of Language: Deacon vs. Pinker

In considering the evolution of human language, I think it is helpful to contrast these two books, and the ideas presented in them:

Terrence Deacon’s “The Symbolic Species: The Co-evolution of Language and the Brain

and

Stephen Pinker’s “The Language Instinct: How the Mind Creates Language (P.S.)

Neither book is exceptionally new, and in fact, Pinker has cranked out a number of books since The Language Instinct. However, I think The Language Instinct is the best of Pinker’s volumes for this discussion. In it, he lays out the basic evolutionary psychology argument in a way that is most directly contrasted with the ideas in Deacon’s. Also, The Language Instinct has a great chapter called (if memory serves) “The Language Mavens” which is worth reading whether or not you agree with or even like the rest of Pinker’s book.

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