Brain Expansion, Persistence Hunting and Cooking. A Chicken and Egg Problem in Human Evolution.

I recently read an article discussing the evolution of modern running and cooking and their respective influence on brain expansion in early Homo. I’m not directly criticizing popular theories about persistence hunting or cooking, because I’m not in a position to realistically do so. But I am in a position to talk a bit about them and offer my own opinions on the ideas.

So, that’s what I’m going to do.

One of the two competing ideas is that the development of persistence hunting allowed our distant ancestors to chase big game animals to exhaustion and kill them easily once they collapsed. It kind of fits. We aren’t very fast but once we find a pace we can keep on going for a very long time, whereas most animals aren’t adapted for that kind of thing…kinda just short distance sprints, enough to get away from most predators.

The second is that persistence hunting couldn’t have played a significant role in brain expansion, because of the amount of caloric expenditure involved in that type of activity. Also, the Hadza tribe was studied and researchers solicited them to engage in persistence hunts, with little success. Interestingly, when unsolicited, persistence hunts didn’t involve running–the individuals walked after the animals and kept them from finding respite in the shade. Once they collapsed from exhaustion, the hunters could easily club them to death.

This led researchers to cooking as the primary driver of brain expansion. Cooking kills parasites, lets meat keep longer before spoiling and makes it easier to digest.

So now…we’re talking the time period right around 2 million years ago. Homo erectus. I can kinda see either idea at play. Erectus had access to fire and tools, brain expansion is very pronounced while they were doing their thing, and they could run pretty well.

But also…it sort of doesn’t quite fit for me, for several reasons.

The first is that there are tools associated with Australopithecus. Sure, erectus was a bit better about it, but if earlier forms had tools, why weren’t they expanding their brains? The second is that fire was also likely scavenged for far longer than it was made, and that (in my opinion) it was probably pretty common place before we start seeing it all over the place. Things are going on before they’re trendy, basically.

Third is that erectus could run, but not as efficiently as we do. It seems to me that a calorically expensive activity, done even less efficiently would be too costly to be a driver of brain expansion. While walking is an option for persistence hunting, it’s a much more complex activity to walk after an animal to conserve energy while simultaneously tracking it’s movements and communicating with others in your group to keep the thing out of the shade. That seems like a more developed form of this kind of hunt. Not better, just one that would have emerged later because why would an individual think to walk after something that could run considerably faster unless it knew there was a payoff? Maybe it was an idea borne of just seeing an animal chased by another, the prey escaped but was exhausted. Easy kill.

I don’t know.

What I do know, though, is that using modern tribes as your argument for what happened 2 million years ago is problematic at best. I mean, yeah, we look to modern hunter gatherers as analogs. But to say that the Hadza walks after animals sometimes, so Homo erectus maybe did it that way just can’t add up, and it also kinda sorta lends itself to the misconception of native peoples as primitive and less developed than Europeans. No, that’s not what the researchers meant to suggest, but it will always be something that should be treated carefully.

Furthermore, the Ju/wasi would persistence hunt. Before western culture ruined their way of life. Elizabeth Marshall Thomas documented in the 50’s, individuals running down eland to exhaustion. If we are going to use modern peoples as analogs, we need to be thorough. If both running and walking exist as hunting methods in hunter gatherer populations, we have to consider that both methods existed in the past.

We also have to stop buying into and perpetuating the myth that hunting and gathering as a lifestyle still exist. They don’t. The people coaxed into hunts by researchers are hunter gatherers by tradition, but not practice. They are the children and grandchildren of hunter gatherers. They might know a bit more about it than you or I, but it’s not how they’re surviving anymore. And it hasn’t been for a long time. 

So, what do I think?

Well, always I am looking at competing hypotheses and theories and looking at what makes an occurrence seem like it’s just not a big deal. Of course, it was a big deal. But at the time? Early homo wasn’t flipping out and bragging about their steadily increasing cranial capacity. That sounds idiotic. It’s a big deal retrospectively, and obviously it’s a pretty legitimately big deal that we got our big brains and invented computers and language and stuff. But at the time it was just individuals doing their respective things and trying to survive.

For me, what makes it the smallest deal is a bit of a synthesis of the ideas. First, these tendencies had to exist earlier than we see them. We aren’t finding the literal first individual with an expanded brain. When we find evidence of cooking, it isn’t the first meal ever cooked. When we find a tool, it isn’t the first one. When we find an individual adapted to running, it means that that adaptation was selected for before it was improved upon by evolution.

By the time we see evidence of any of this, it had been going on for some time.

To drive brain expansion, we absolutely needed access to higher quantities of higher quality food sources. Cooking would allow for better digestion and absorption of nutrients from animal (and plant!) food sources and allow that food to keep for longer, but we still needed more of it. Without first having that access, would an individual have risked the expenditure of chasing down an animal, either running it down or spending several hours in the hot sun walking it down? It’s a big risk, and without a guaranteed payoff, or other options for food, I’m not so sure it would have been a common practice.

One thing that seems reasonable to me is access to aquatic food sources. In east Africa, where some of the earliest evidence of our ancestors is found, there are some really big fish. Catfish. These critters pull themselves onto shore to spawn, and they are huge. They also can’t move very well on land…they’re fish.

At assemblages associated with early homo, catfish pectoral spines are found. These spines are on average considerably larger than those found in naturally occurring fossil deposits. This is a strong suggestion that early homo was taking advantage of these critters as a food source. They can’t move, there’s little risk of injury. Just walk up and slam a huge rock on the bastards and you’ve got a large quantity of very excellent food that offers less risk of foodborne illness if consumed raw.

With the presence of a good food source like this, riskier attempts become less risky. You might not be at risk of injury when chasing down an animal (if you know what you’re doing), but if food is otherwise scarce, you’re going to play it safe. But, if you just smashed the bejesus out of a 5′ long catfish and have some food anyway, you might go for it. Especially if you know that cooking whatever meat you get will let it keep long enough to actually consume it all.

Earlier than erectus, there has to have been the tendency toward some kind of behavior that would select for both endurance running and brain expansion, because it will not be present in a population unless it’s been going on for a while–it’s not going to appear out of nowhere without precedent. My opinion is that giant catfish (for example) would provide fairly reliable access to brain-feeding foods that could be obtained without any kind of sophisticated weaponry, would be easily butchered and could be consumed raw with less risk than other meats.

The access to cooking was a benefit that could easily be attributed to accident (scavenged victims of wildfire, for example) and once fire was scavenged it would be easy to see the benefits of cooked meat. Once fire could be produced it would have been a game changer. The introduction of more complicated persistence hunting was a product of already expanding brains and increasingly complex behavior.

Really that’s what fits for me. No one thing would have directly driven anything. It wasn’t a eureka moment of “hey lets walk after that huge animal because maybe it will get tired” or “I bet that thing will get tired before we do if we run at a good pace.” It was a merging of lifestyle and biology that allowed for greater calculated risk with greater payoff, with other options to buffer the effects of failed hunts.

The lifestyle would have been extremely difficult, and my mindset is always that the easiest procurement of food would have been favored. More complicated behaviors with greater risk and the need for enhanced communication could only have existed in societies that could afford to try them. I don’t think these behaviors popped up as suddenly as they appear in the fossil record; rather, it was a slow gradation and easing into a new behavior and way of life as circumstance allowed.

I don’t think we could have suddenly been chasing down prey without the guarantee of another food source. And I don’t think our brains would have arbitrarily expanded without an increased pressure on cognition. Plenty of animals have awesome access to food and don’t have the kind of encephalization we do. With evolution, you aren’t just given something. You get something if you can do something a bit better and it makes it more likely that you’ll reproduce. Bigger brains and intellect had to have a reason to have been favored, and once they were favored they needed to be fed.

Soooooo, access to an easy and awesome food source would have allowed trials into more complicated and risky ways of hunting. Providing both the niche as well as the fuel.


About Pedal Powered Anthropology


Posted on 10/24/2015, in Paleoanthropology, personal perspectives, Primatology., Scientific conjecture and tagged , , . Bookmark the permalink. Leave a comment.

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