It is often very hard to recognize when similar elements were deployed in different social and cultural systems in the past, as I argue is the case h… - Judith Sealy

Bone tissue accumulates over many years, so this was a long-term dietary pattern. People buried at Matjes River Rock Shelter, on the other hand, ate much more mixed diets, with more terrestrial food or low trophic level [low on the food chain] marine foods, such as shellfish.

What's surprising about it is the degree of specialisation in local resources, from which we can infer that these people were living within relatively small areas, rather than trekking regularly across large areas of landscape. This is unexpected, given the very mobile lifestyle of most recent southern African hunter-gatherers.

There is an extensive literature on the use of ethnography in archaeology and the dangers of simplistic assumptions that past societies were necessarily like recent ones.