Saturday, January 29, 2005


Acheulean Hand Axes Ought to Tell Us Something, But What?

An ultimate issue for understanding ourselves is explaining sources of cultural change and how culture is transmitted and organized between people. This makes what archeologists of pre-history say about the so-called Acheulean hand axes so interesting. (I re-developed this interest recently through reading Matt Ridley’s provocative and fascinating Nature via Nurture.) These chipped stone tools apparently were made by proto-humans for well over a million years; then more complex tool sets appeared, and the hand axe was soon no more.

A look at representative hand axes suggest that they may have been altered a bit over this tremendously long time period. But two things seem remarkable. In evolutionary time, a million years is extremely long; most species don’t last so long, and one would imagine culture by its nature (so to speak) to be more variable than biology. In fact, it does seem that quite different proto-human species continued the hand-axe culture. So the sheer survival value apparently imparted by the possession of this one simple tool must have been enormous.

And yet, if this one invention was so valuable, why were creatures who were able to develop it not able fairly soon to go further, to invent more specialized versions?
Some possible explanations:

1. The hand-axe users were not capable of the level of social cooperation that would have made more specialized tools work better.

2. The hand-axe users were very limited in their ability to learn new skills, so that in effect, to develop new tools would require giving up old ones. This seems unlikely since hand-axe users in fact seemed to flourish in a variety of different environments which would have required some specialized learning, though perhaps of a different kind than tool-making.

3. The hand-axe users had a very limited capability of passing on skills. This could have been partly due to cultural limitations, and partly due to genetic limitations. Thus a cultural limitation would simply mean that better modes of cultural transmission, while biologically feasible, simply hadn’t been invented yet. One such limitation might have been that fathers, though nearby during the raising of their offspring, had not yet gotten involved in teaching anything to them, or in effect being directly responsible at all for raising them, except possibly by offering protection and perhaps some nourishment, perhaps indirectly. (Sorry for all the qualifications, which wouldn’t be here if I had more recently in mind what our apish relatives do and what the fossil records might show. Evidently, orangutan males play little role at all in raising the young; male gorillas, from my own zoo observations, do little also, and from what I remember of Jane Goodall’s work, male chimps also do little. On the other hand, also from my own zoo observation, male siamangs seem to play a role equal to that of females in raising their young. Thus it is certainly not beyond the general ape pattern for human males to be involved in raising their young, and in so doing, to pass on culture if any, but it seems very possible that until quite late among proto-humans, this didn’t happen.

4. It is also possible that while the proto-humans in question could have invented more techniques – that is that their brains were complex enough to handle this easily — a kind of conservatism about preserving existing behaviors and not diluting them with new ones prevailed. We know that a strong degree of conservatism prevails among most humans today, and is particularly marked among children of about four(?), at least in certain matters, such as rules of games, gender roles, or eating patterns. And then again among many old people. It could be that the intermediate period of exploration and adventuresomeness was a later development for proto-humans. That would raise the question of how the hand-axe revolution happened in the first place, but one can imagine scenarios in which, for a small group, conservatism broke down, the revolution in tool-making took place, and then through contact or interbreeding with a larger group, the prevailing conservatism was re-established, but now with the hand axe as an exception.

5. But perhaps most likely is that once the hand axe was in use, further innovation would have required a denser population, to permit the necessary division of labor, on the one hand, and on the other to allow enough innovation to occur and be passed on successfully to enough “early adopters.”

I shall return in future to the question this raises about why population might have stayed below the innovation limit for so long.

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