All this means is that the approach to explaining problems in human life and history will include data from, say, linguistics, archaeology, population genetics, environmental sciences, and whatever else, instead of looking at only one avenue. It doesn't refer to a structural-functionalist view of society or the endorsement of the organic metaphor of human societies or any other holist claim, and it has nothing to do, in any real sense, with ontological holism (which, again, I would define as the view that something exists other than what actually exists; or that something is going on other than what is actually going on; or the view that wholes really are more than their parts). It is based on the idea that in order to explain the diversity or history of Homo sapiens sapiens, we have to use all the available data rather than restricting ourselves to petty, arbitrary, disciplinary boundaries or privileging one strand of evidence over all others.
This to me sounds a lot like common sense in action, and integrating the disciplines concerned with human life seems like a necessary and important step. It was anticipated long ago that this kind of synthesis would revolutionise our understanding of the human past (and consequently the human present), and the early 'four field' approach to anthropology was an obvious precursor, but it has only been in the last few decades that the fruits of this synthesis – this so-called ‘holistic’ approach – have been able to provide powerful, compelling results. Patrick Kirch’s work is exemplary in this regard, but it has been used almost everywhere else besides the Pacific, as well. I have recently been reading a series of articles (on my lovely new Kindle Fire) by Penn State archaeologist Dean Snow about the Iroquoian language family, in which a range of evidence is used to place proto-Northern Iroquoian in Pennsylvania c.900 CE, associated with the spread of matrilineal descent groups, matrilocality, and maize agriculture into New York and Ontario (and elsewhere) over the course of a few hundred years (this is actually a controversial assessment, and it seems to fail on the archaeological evidence, which doesn't fit quite right). This ‘holistic’ approach can really open up the prehistory of our species in an extraordinary way, and we’re seeing it all over the place, whether called ‘holistic’ or not (I’d prefer not, of course).
This is the kind of holism I can get on board with. The other kind – the kind with which it is often confused, and which is, in reality, a truer and more accurate use of the word ‘holism’ – can and should be dispensed with, as a reductionist view of human society is the only possible naturalistic view.* Objections to reducing human social facts to some set of generalizable human mental states seem to me misguided. The view that we should adopt a truly holistic view in understanding people and their lives appears to be based on the idea that holism is a friendlier and nicer term/idea than reductionism, rather than on the real merits of the ideas themselves (which may be why ‘holism’ and ‘holistic’ are also the preferred terms in New Age medicine, TCM, and other pseudo-scientific movements).
I think we could therefore differentiate between three kinds of holism in social science. One is the Durkheimian kind, that sees 'the social', or some other notion, as more than the things that compose it. This is ontological holism as applied to human society. The second is explanatory kind, that takes wholes, like 'Indian Ocean trade' or 'rate of inflation', to exist for explanatory purposes and treats them as if they have properties of their own. I suppose this could be called explanatory holism, but I'm not sure that's a useful term (see this interesting free paper that grapples with these same issues). The third is this synthesis kind, that takes 'holism' to refer to a synthesis of the evidence and disciplines available. These are clearly different things. Durkheim's radical social fact holism is completely different to the latter two approaches to explaining social facts, and this synthesis approach isn't holism at all. I don't know what else to call it, though. The scientific approach, perhaps?
I just saw an article on JSTOR which uses this very trope - holism being the use of multiple data streams. See here. The author, Robert Borofsky, argues that the 'four-field' approach is largely a myth; very few articles in American anthropology ever attempted to unify the evidence from these fields in understanding humans. Borofsky then calls for more 'holism' in anthropology.