Thus, it would appear that Bushman groups throughout the Kalahari have access to a number of nutrient-dense and often quite abundant plant, animal, and insect resources that become available at more or less the same time of year that they undertake much of their big-game hunting. This intriguing temporal convergence raises the possibility that the San hunt these animals for reasons other than fat or protein. Perhaps, instead, it is precisely because of the reliability and high fat and protein content of mongongos, baobabs, tsin beans, marula nuts, mopane worms, and others that Bushman hunters are able to afford the “luxury” of engaging in such a time- consuming, failure-prone, and costly activity… In other words, an explanation for their hunting behavior may well lie beyond the strictly nutritional realm.

Speth is also mentioned (disparagingly) in the fascinating paper referenced in this post, which offers a lot of speculation built on good science data about nutrition and the human gut, in addition to the archaeogical finds.