Why we need such big brains part 2 – Ask the Bushmen

As you may recall from the previous post on the subject we are dealing here with two hypotheses generally referred to as “Specialization” and “Versatility”. In other words did our brain grow to enable us to hunt more efficiently (Ben-Dor et al) or to enable us to increase the versatility of our food (Ungar et al) I.e. to increase our ability to source plant or animal sourced food at will?

We saw in the previous post that evolution, in the case of E. coli metabolism, chose to optimize for one food source while allowing limited sacrifice of optimization to allow a measure of flexibility at minimized cost.

Intuitively I find it hard to comprehend how the intellectual demands that are associated with hunting can be equated with those needed for plant food gathering. I mean even a donkey knows what it can eat and where to find it. A baboon in the savannah picks up about 3000 food items a day. With a brain that is quarter our size (adjusted for weight) it knows where to find them and which items not to pick.

Conversely hunting is  a dynamic situation where an animal (us) has to catch and kill another animal that never stays in the same place, is faster if it escapes and stronger if it attacks and all this without a useful sense of smell and without natural killing equipment like adequate teeth, nails or venom. It therefore always seemed rather obvious to me that it can only be hunting that demanded really  big brain.

Few days ago I came across a rather old paper that may add support to the notion that we needed big brains mainly in order to hunt animals. The 1976 paper is called “!Kung Knowledge of Animal Behavior” by Nicholas Blurton Jones and Melvin J. Konner (1). The !Kung is a tribe of hunter gatherers that lives in the Kalahari desert of Southern Africa.

Blurton and Konner were initially interested it seems in animal behavior but this paper is really about epistemology, namely how the !Kung obtain, communicate and organize their knowledge concerning animal behavior.  One thing is evident from the paper – there is a lot of knowledge and it is solid. Blurton and Konner are quick to note that the! Kung “were very careful to discriminate data from theory and interpretation, and even more so to discriminate observed data from hearsay”. They admitted ignorance very readily, argued about generalizations based on scant data, were skeptic at times of others’ observations and their response to skepticism “was never defensive and it typically led to a long and careful description”.

The paper lists many examples of knowledge of animal behavior and hunting. Reading through the paper, the similarity of the intellectual process that is used in the hunt with the common scientific method is impossible to ignore. One also has to take into account that unlike science it is preformed under time, emotional and physical pressure. In Blurton and Konner’s words: “most items of fact must be integrated in a complex way with all the other rapidly changing variables of the hunt. Typically in the course of following the animal a working hypothesis as to his position or condition will be advanced and then tested continually against the spoor”. They describe a case in which Konner accompanied a man in following a gemsbok (antelope) spoor which the man said were made this morning. After about twenty minutes the man abandoned the spoor because he decided that it was made last night on account of a superimposed mouse tracks inside one of the gemsbok’s hoofing prints. Mouse is a nocturnal animal so the man deduced that the gemsbok’s spoor were from last night.

The authors list a number of predictions that a hunter must make recurrently during hunts like: “Where is the animal now? Which way is it going and how fast? Is it likely to stop or to reverse direction? Where and how seriously is it wounded? How long will it live?” in making the predictions the hunter must take into account “the time of year, the time of day; heat; wind; terrain; depth, shape and displacement of tracks; condition of feces; condition and displacement of grass, twigs and shrubs along the spoor; amount, position and color of blood on the ground, grass or bushes and the store of knowledge concerning the behavior of different prey species, especially when under attack”.

It is no wonder then that the !kung listed the following mental qualities as essential in hunting: “knowledge, sense, cleverness and alertness”.

Noting that repeated activating of hypothesis, trying them out against new data, integrating them with previously known facts and rejecting ones which do not stand up are basic features of human mental life Blurton and Konner come to the conclusion that they were required for “the very way of life for which the human brain evolved”.

In other words the most “basic feature of human mental life” are the ones which evolved to allow us to hunt.

And finally, when one compares the mental demands of hunting to the relatively static, simple template, that is agriculture, a possible explanation to the shrinkage in brain size that we have experienced in the last 20,000 years emerges. Evolution is not directional. If we don’t need it there is no point in feeding it. That brain shrinkage also doesn’t tie up well with another hypothesis on why we have such big brains namely “the social relations hypothesis”. This hypothesis posits that it is our increasingly complicated social interactions that demanded such a big brain. It is quite obvious however that the complication of our social interactions practically exploded during the last 20,000 years since sedentism began in the Epipalaeolithic and yet our brains have shrunk from an average of 1500 cm² to 1350 cm² and are apparently continuing to shrink as we speak.

Luckily we still have to come up with hypotheses from time to time and attempt to test them or we could have ended up foraging the supermarket lanes with a baboon size brain…

(1)    Blurton Jones, N.G., & Konner, M.J. (1976). Bushman knowledge of animal behavior. In R. Lee & I. DeVore (Eds.), Kalahari hunter-gatherers (pp. 325-348). Cambridge: Harvard University Press.

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