That’s your answer?

17 03 2007

I managed to finish Upright by Craig Stanford this afternoon, and I can’t say that I would recommend the book. When talking about anthropology and debates about the origins of humanity, Stanford provides plenty of information on varying hypotheses, ultimately concluding that we need more information. When not on the subject of what scientist thinks what, however, I can’t say Stanford shines, and I his hypothesis for why primates became obligate bipeds falls short.

As I mentioned in an earlier post, ecology plays only a minor role in the book, when in reality it is going to be absolutely essential to understanding the pressures that allowed bipedalism (including changes in the inner ear, center of gravity in the body, etc.) to develop. While Stanford may be correct that since we know from the Laetoli footprints are 3.7 million years old bipedalism (at least in a form approaching our own) must have been developed earlier, during a time when the primary land cover was forest, not savanna. Hence, the “looking over the tall grass to see predators” hypothesis doesn’t seem to hold, and Stanford points to current chimpanzee behavior in an attempt to solve the puzzle. Sanford hypothesizes that bidepalism developed as a result of chimps standing up and pulling down branches in order to get leaves/fruit, thus providing the impetus for developing a two-legged posture. While this may have played a role in primates “standing up” for the first time, I think it is far from the answer we’re looking for.

First is the problem of taking a behavior observable today and ascribing it to a similar hypothetical animal in the past, whose behavior we do not have access to. This sort of behavior (simply reaching up to grasp a branch and pull it down) is likely to have been exhibited for millions of years, and if it truly was the key to becoming an obligate biped I wonder why there are simply not more of them. Stanford also points to gibbons sometimes walking upright in trees for short distances, but it is important to remember that they do not do this for any great length of time and require strong, grasping feet in order to stay on the branch; feet like ours are not well adapted to running through the trees.

Stanford also notes that often times when a chimpanzee pulls down a branch to get more fruit, it will often share the spoils with allies and family, thus if the behavior did in fact provide a selective advantage it is nearly blocked out being that other members who do not exhibit the behavior reap the benefits. The behavior also seems to have more to do with arm strength and pulling the branches down than standing up and walking about, the feet acting as more of an anchor and so there’s no reason to chance foot structure, leg structure, balance, etc. Chimpanzees are certainly capable of standing up and can do so for short periods, and while I need to look into it more, some footage from the BBC may give us some clues as to what provided the selective pressure to turn primates into bipeds.

There are some populations of chimpanzees that live in areas subject to flooding, the chimpanzees sometimes have to transverse the flooded areas. In the last episode of the Life of Mammals series, several chimpanzees are shown standing upright, wading through the flooded area. If they were to knuckle-walk, their faces would be in the water and babies hanging onto their mothers might have been as well, thus the water requiring an upright posture. This may very well not be the answer scientists are looking for, but I think it’s far more interesting and reasonable than Stanford’s hypothesis. I would imagine that for bipedalism to develop and increase in frequency in the gene pool, there would have to be some advantage to it that wouldn’t be neutralized by altruism as Stanford describes; there would have to be some pressure and exhibiting bipedal behavior would likely serve as an advantage. To his credit, Stanford is correct that in this case behavior came before morphological change, a saltation that would create different legs, a spinal column, inner-ear structure, center of gravity, etc. only existing in magical thinking. Indeed, this is not a black and white issue of standing up all the time vs knuckle walking, but there would have to be some distinct advantage to standing up in a population, the advantage likely becoming more pronounced as ecology changed. Indeed, we know that the forests gave way to savannah, and so ecology would then favor those that could travel long distances more efficiently and be able to spot trouble further off, the equivalent of developing bipeds winning the lottery; if the ecology changed in a different way, bipedalism might not have developed.

It also disturbed me that Stanford talks about developing towards humanity, but he never defines what “human” is, whether he’s using it as an inclusive term for hominids or just for members of Homo sapiens. This is a minor point, however, and I won’t dwell on it for there’s something I find even more contentious. The last chapter of the book, rather than summing up prehistory, looks to the future and Stanford suggests that if we are to find intelligent life in the universe, such beings will likely look like us. Stanford gives no reason to correlate bipedalism with intelligence, but he says that since life elsewhere would be subject to the same rules as far as evolution, we should expect upright, intelligent creatures with paired limbs and a variable number of digits. To support this notion, he says that in Australia there were marsupial lions, marsupial wolves, etc., a kangaroo essentially being different from an antelope only in the way it moves. This, of course, is complete and utter bullshit (pardon the expletive; I save them for moments like this). Stanford likely heard the popular notion that there was a parallel evolutionary pattern in Australia featuring marsupials rather than placentals, but it is clear that he did not do any more research into the topic. Surely, many of the same general niches were available in Australia as in other places (noctural predator, diurnal short-grass grazer, noctural generalist, crepuscular scavenger, etc.), and given that the large fauna of Australia were mammals (built on a tetrapod body plan) it is not surprising that the niches were filled by superficially similiar animals, but to say there are no differences between a gerenuk and a red kangaroo other than locomotion is absolutely absurd.

If Stanford knew more evolutionary history, it would have helped the ending of the book as well. There have been all sorts of body plans in the past, especially prior to and during the Cambrian; if ecology had been different who knows what body forms might be prevalent today. To suggest that if there is intelligent life elsewhere it must be like a primate is short-sighted, and it certainly doesn’t take into account that even though such creatures would be subject to physics, chemistry, and evolution, those may all vary greatly on a planet of a different makeup, size, rotation, etc. Even if we had an exact duplicate of earth and could start life all over again, I don’t think we’d come to the same results as we see today; there is no march towards progress that dictates that only our body form can possess intelligence. Indeed, Stanford chastises those who believe that evolution has a goal earlier in the book, but succumbs to a similar hubris in the conclusion of his book.

This isn’t to say the books is worthless; Stanford provides some interesting history of anthropology and various debates, but outside of this arena there isn’t much I can say I enjoyed. The book is brief and plainly written, only about 175 pages and of a small size, but adding some more illustration (i.e. skeletal diagrams, maps of migration, changing ecology) and explanation could only have done the book good. In any event, now I’m going to pick up David Quammen’s Wild Thoughts from Wild Places, which I hope will be more enjoyable.



One response

16 09 2011

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