Compare the Bushmen and the Ulithi in terms of subsistence activity?

Question

Why does anthropology focus on subsistence as a “first premise” in the study of human cultures?

Answer 1

While the San people are dispersed across a variety of settings in sub-Saharan Africa and have developed a variety of subsistence techniques falling broadly into the class of hunting & gathering, the Ulithi people are limited to an atoll in the Pacific Ocean and derive subsistence mostly from fishing.

As for the traditional sequence of subsistence (beginning with hunting & gathering), it has very generally traced the development of all major cultures in history from the Near East to the Americas.  Thus, it has become a fundamental 'premise' anthropologists use to gain a first-order approximation of the development of a culture under investigation (particularly ones which only exist today in the fossil record).

As for the precedence 'subsistence activity' takes in anthropological inquiry, it turns out what and how much a culture produces goes surprisingly far in delimiting how much a culture can achieve.  A plethora of factors that define a culture -- including its agriculture, pottery, metallurgy, writing, transport, folklore, and even recreational drug use -- can be traced back to how a culture kept its members fed.