I’ve referred to Virpi Lummaa’s research on the Grandmother Hypothesis using Finnish records a fair amount, check out this new paper (Open Access) using Gambian data. There are other papers and studies (use books.google.com for this) among groups like the Khasis and Bengalis (Khasis = matrilineal & matrifocal, Bengalis = patrilineal & patriarchal, but both show maternal grandmother effect). Generally the results are often ambiguous, but what directionality there is in the data implies some relationship between maternal grandmothers and fitness. Most workers have a pretty straightforward interpretation that the bias toward maternal grandmothers taking an interest in their grandchildren, but less so paternal grandmothers, is a function of past human mating patterns. There has long been debate about whether patrilocality or matrilocality was more the norm genetically (early genetic data implied the former, more recent work has clouded the issue). Ethnographic surveys from anthropology tend to show a bias toward patrilocal, and often patrilineal cultures. But, there is also a tendency to see these features more often in “large scale” as opposed to “small scale” cultures (and historical records show a shift from matrifocality toward patrifocality as societies become more “civilized,” e.g., Japan or Southern India). I have alluded to the fact that I believe that the last 10,000 years and the Neolithic Revolution resulted in the emergence of new and often constraining cultural adaptations, I believe that normative patrifocality is one of those.1 Though I do believe in the power of recent human evolution, I think that time lag is probably more likely in something as complex and contingent as the physiological of menopause and the evolutionary logic which drove it (just like romantic love, which was also quite often an irrelevancy or obstacle for high status lineages for whom mating was a material exchange between consenting cartels).
1 – Indo-European cultures often alluded to a special affectionate role for the maternal uncle. And yet note that nominally they were generally patrilineal cultures. This is one case where action and theory might have varied systematically.