Social science rarely connects with this basic point. Anthropologists like to adhere to different forms of causation, both in terms of the rejection of the nervous system as the cause of human action (an absurdity!) and in terms of explaining human actions in terms of ill-defined, amorphous 'social' forces. This places much of anthropological work, even the stuff that makes sincere attempts at causal explanations, on a non-naturalistic footing. Instead of saying that 'social forces' of some kind have a causal role to play, we have to ask beforehand what a social force could possibly be - how it could cause actions in the first place.
The nervous system is regular. It works in consistent ways. Its operations have been studied in-depth by generations of astute and sensible observers, and when insights from this process have been applied to ethnographic information, a great deal of useful stuff has resulted. If we think of everything humans do in cognitive term (in principle) then we can really begin to understand complex phenomena, like all the rules and regulations humans have and live by - we can really start to understand 'social facts', instead of taking them for granted, and we can start taking apart 'culture', human actions that vary by upbringing and society and so many other variables.
All causative explanations in the human sciences have to take it as given that the causes of human action are to be found in human minds/nervous systems. Or, as Razib Khan put it in another recent post (found here),
Just to be explicit, an understanding of evolution or genetics is not necessary to gain a first order understanding of the nature of the phenomenon of human culture, but cognition is.In order to really understand how people work and why they do what they do - basic aims of any part of any study of human beings - we have to look at how brains and nervous systems work.