Learning of course has two sides, the learning and the teaching. Cultures all make concerted efforts to pass onto the next generation whatever they think is important. But how do they decide what is important? This is a fascinating puzzle. Some traditional knowledge strikes us as extremely useful, but other parts seem silly. One of Henrich's main arguments is that we preserve a lot of strange cultural rules and the like because it is very hard, in fact often impossible, for any single person to figure out which parts of the culture are important and which are not. Henrich has many illustrative examples, one of which concerns raising pigs. In the New Guinea highlands raising pigs is a supremely important activity, since the prestige of a community is tied up in how many pigs they can serve to guests at important feasts. In 1971 anthropologist David Boyd visited the village of Irakia and found the community immersed in a debate about how to fix their own lagging pig production. It is proposed, and eventually adopted that they should "follow the Fore," that is, adopt the pig-raising techniques of the Fore people, who have lately been very successful in this department. Here is the actual list of measures adopted by the village:
1) All villagers must sing, dance and play flutes for their pigs. This ritual causes the pigs to grow faster and bigger. At feasts, the pigs should be fed first from the oven. People are fed second.We look at this list and think that some of it is highly relevant and some is not. But how do we know? The people of Irakia presumably know a lot more about raising pigs in New Guinea than any of us, so why do we think we know that, say, playing music to pigs does not help them grow? But anyway the point is that the Fore way of raising pigs was adapted en bloc because that is just how people work most of the time. The thousands of particular actions that make up something like hunting deer or growing potatoes or holding feasts are rarely scrutinized in themselves; they are part of the way, and if the way is good, if the way is working, then we keep doing all of them.
2) Pigs should not be killed for breaking into another’s garden. The pig’s owner must assist the owner of the garden in repairing the fence. Disputes will be resolved following the dispute resolution procedure used among the Fore’.
3) Sending pigs to other villages is tabooed, except for the official festival feast.
4) Women should take better care of the pigs, and feed them more food. To find extra time for this, women should spend less time gossiping.
5) Men must plant more sweet potatoes for the women to feed to the pigs, and should not depart for wage labor in distant towns until the pigs have grown to a certain size.
So when you ask, why do people cling to ideas that strike you as outmoded, from an anthropological standpoint the question answers itself: because cultures that passed on their ways of doing things survived, and those that did not have disappeared. You may think that you can reason your way to improvements, but this is a particularly modern outlook that would have seemed bizarre of most humans of the past, and anyway you are probably wrong. (See: communism, libertarianism, etc.)
Life, even in a neolithic village, is simply too complex for any person working alone to reason out a better way of living. So we evolved a very strong attachment to old ways.
I think the best way to see all the weirdness of the modern world is through this lens. We have created so much change, so fast, that clinging to old cultural ways no longer makes sense in many, many areas. This has unmoored us and left us floundering about, prey to ideologies that offer something solid to take the place of tradition. But this is illusion; the world is too complex for ideology, just as it is too complex for reliance on tradition. So we suffer from anxiety and rage and all the other modern diseases.
I should say that I think this picture is highly simplified; along with our general attachment to tradition we humans also have a thirst for novelty that is in some of us extremely strong. After all cultures do change, even the most traditional. But for most of our history they changed very slowly because that was the best guarantee of survival, and our poor brains, which evolved for the slow pace of peasant life, are at sea in this crazy modern world we have devised.