Wednesday, December 26, 2012

Savanna Confessions

Red Colobus Monkey
So maybe I was wrong. Sort of.

It’s no secret that I’m not a fan of the savannista hypothesis, despite its considerable popularity within the profession, primarily because it doesn’t account for demographics. It flies in the face of our current demographics. I begrudgingly accepted that early hominins harvested the grasslands, but I was skeptical of the disappearing forest as catalyst for their abandoning the protection of the trees. It appeared crystal clear to me that something had to draw the people down from the trees; they couldn’t have been forced out; evolution doesn’t work that way. It was also fairly evident that that something was meat, and that the protection was weaponry. Quite why meat suddenly became important for an isolated group of simians, I hadn’t worked out.

Nonetheless, most people in the profession still insisted that the disappearance of the forest and the simultaneous emergence of hominins couldn’t have been coincidental. Furthermore, hominins were beginning to harvest the grasslands; they were certainly eating small ungulates and vertebrates, as well as turtles. Given our demographics, it is unquestionable that at some point humans moved to the waterside, but that’s another question; they first have to get out of the trees.

The problems with leaving the trees, of course, is that it’s, exceedingly difficult to change ones eco-niche. As a rule, when an eco-system disappears, all components of the system disappear, as well, plants and animals. That humans didn’t disappear when the forest disappeared says that, self-evidently, their food source didn’t disappear along with the forest; which in turn implies that their food source wasn’t entirely dependent on the forest.

Stepping back a minute and looking at the pre-split simian, back when chimpanzees and hominins were a single species, and considering that today’s chimps are regular hunters who fashion their own spears and considering that humans are currently hunters, it’s most likely that the pre-split simian was also a hunter who fashioned his/her own weapons/tools. And that simian was already spending considerable time on the ground. That being the case, when the simian species split into two groups—a necessary condition for species development—possibly by the growth of intervening grasslands, it could well be that one of the two groups was caught in an island forest that was slowly disappearing under it. For many, if not most, of the inhabitants of that eco-system, it meant their disappearance, as well.

These chumans (chimps becoming humans), though, had a diet which included meat. Their main meat, if current chimps are any indication, was probably monkeys of one sort or another; although chimps are known to eat as many as thirty-five different vertebrate species, which includes small antelope. One can imagine that, as the forest disappeared, not only did the plant matter on which the chumans depended disappear, so did the monkeys. Fortunately, though, small ungulates didn’t disappear. In fact, with the spread of the grasslands, so would many types of antelope spread. It might have been fairly easy for the chumans to switch to an antelope versus a monkey dominated diet. And, if the plant material which the chumans were accustomed to eating began to get scarce, it could well be that those chumans who we better at and relied more on meat for their diet, out-paced those still dependent on forest products. In such circumstances, a species could change the ratio of its diet fairly quickly without changing its basic dietary needs. And by such a process, chumans, by now hominins, could have adapted fairly quickly to a disappearing forest. Concomitantly, it also meant that the newly minted hominins would have to spend all their time on the ground if they were going to be successful antelope hunters.
Okay, I’ll give you that. That’s a likely scenario which covers the savannista basics. It gets people out on the prairies. It does, per force, get them out on the prairies as hunters. I’m sure the defensive value of spears wasn’t lost on these early ancestors of ours, as well. What this undoubtedly starts is the human habit of tracking down animals over long distances, killing them, and transporting the meat back to the main group/tribe/family. Given that one’s hands are occupied with either weapons or kill, it behooved one to stand up as straight and as efficiently as possible; and those that did so easily were rewarded with successful hunts. Natural selection will select for upright bipedalism, as it did.

In defense of my original argument, that evolution is governed by opportunity, not necessity, still holds true. The hominins weren’t forced out of the dwindling forest, they were enticed out by by a new abundance of game, a shift from monkey to antelope. If there is a significant problem with this scenario, it’s that our shift towards obligate bipedalism occurred some three million years before the thinning of the forest, but who’s counting? And we shouldn’t forget that the hominins had no idea the forest was thinning; they were simply out hunting like they’d always done.

But this hunting scenario has other requirements. I would argue that, by adopting hunting as a regular part of our alimentary scheme, we were forced to adopt other regular practices of predatory animals, among them the establishing of temporary dens, lairs, or nests where the young are raised until old enough to participate in the hunt or other harvest. I would argue that, from the time we left the trees, we made those lairs down by the water (if for no other reason than we were reluctant to give up the trees until the last minute and that the last trees in the grassland cleaved close to the waterways), and we haven’t moved from there since. Sure, we covered immense territories in our hunting forays, but when we came back home, it was always down by the stream, on the edge of the swamp. That would account for our current demographics.

So, how does that hypothesis fit? Have I left anybody out?

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