From Nature, an interesting but puzzling abstract:

In modern societies, there is a decreased usage of traditional weapons to settle interpersonal or inter-group disputes compared to usage in traditional societies, possibly affecting the frequency-dependent selection on the handedness polymorphism.

If your culture does a lot of fighting with swords or spears, is it better to be right-handed or left-handed? As Rocky points out, lefthanders are widely assumed to have an unfair advantage in boxing, but I don’t know about about edged weapons.

Another societal difference is the extensive automation of hard manual labour (including agriculture) in industrialized societies, relaxing the selection for hand specialization.

Thus, selection of handedness is likely to differ between traditional and modern societies. As heritability determines the relative speed of evolutionary dynamics, handedness heritability was compared between industrialized and non-industrialized societies.

First, individuals were sampled from a non-industrialized area in Indonesia, where violent conflicts are relatively frequent and tribal wars have been prevalent recently. Handedness was recorded directly or indirectly for 11,490 individuals belonging to 650 independent pedigrees, and handedness heritability was estimated using a pedigree-based animal model.

Second, estimates of handedness heritability derived from published sources were collected to compare heritability estimates, accounting for various confounding variables. Non-industrialized countries displayed a significantly higher heritability value (h2 = 0.56) than that of industrialized countries (h2 = 0.20).

Heritability decreased with time along the twentieth century in industrialized countries, independently of the frequency of left-handedness, and independently of the method used to measure handedness. In conclusion, the data are consistent with a decrease in handedness heritability following the industrialization process and/or the associated decrease in violence using traditional weapons. The difference in heritability between industrialized and non-industrialized countries suggests that selection of handedness is thus likely to differ between traditional and modern societies.