There are a couple of common explanations for this:
- One explanation invokes DNA evolution. This explanation says that acquiring intact memes was beneficial to their hosts - and so acquiring them without error was favoured.
- The other explanation involves cultural evolution. This suggests that culture evolved in order to improve its copying fidelity. Gesticulation led to grunts, which led to speech, which led to writing, which led to printing, which led to the internet - with the copying fidelity increasing at every step. Here the benefits of high-fidelity copying accrued primarily to the memes involved - not to genes.
Recently, I've seen another kind of explanation which involves cultural kin selection:
In DNA-based kin selection, your genetic relatedness to another human is an accident of birth - something that you can't easily change. The best you can do is to try and manipulate perceived relatedness cues. In cultural kin selection, the situation is a bit different. The proportion of memes you share with another human is not fixed. You can fairly easily increase your memetic relatedness to another human - by the process of acquiring memes from them - or perhaps their teachers or associates.
It has long been known by psychologists that humans manipulate other humans by imitating them. Interview technique books are full of advice about mirroring your interviewer's posture and copying them in other ways - in order to appear more similar to them. The idea is that this process may have actively pressured humans into improving their imitations skills - in order to appear more similar to other humans, so as to better manipulate them. The improvement could have involved DNA-based genetic evolution, cultural evolution - or a combination of the two.
This is an intriguing story - partly because we can see the process involved acting today. However, I think the idea needs more comprehensive study and quantification. Chimpanzee studies are one area which might illuminate the issue. Chimpanzees have the ability to transmit information down the generations culturally. However do they also imitate each other - in order to appear more like kin to each other? It is an interesting question.
I came across the idea in this article while researching my article on homophily. The paper is in the references for this article. I'm not yet sure where the idea originated.
- Haun, D. B. M., & Over, H. (2013). Like me: A homophily-based account of human culture. [paywall] In P. J. Richerson, & M. H. Christiansen (Eds.), Cultural Evolution: Society, technology, language, and religion.