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Both small-scale human societies and personal social networks have a characteristic hierarchical structure with successively inclusive layers of 15, 50, 150, 500, and 1,500 individuals. It has been suggested that these values represent a set of natural social attractors, or "sweet spots," in organizational terms. We exploited the new phenomenon of permanent (i.e., residential) campsites to ask whether these values are present in the size distribution of the numbers of residents in these naturally small-scale communities. In two separate data sets of different grain, we find consistent evidence for sites with 50, 150, 500, and maybe 1,500 residents. We infer that these reflect numerical sizes at which communities may in some way be socially optimal. Our data do not allow us to say why this pattern emerges, but the consistency of the results and the fact that the predetermined sizes of permanent campsites adhere to this pattern suggest that it may arise from the limits on the number of relationships that make an effective community. [ABSTRACT FROM AUTHOR]

It has been suggested that parish-based reconstitution studies may underestimate the true age at marriage because they do not normally include data for emigrants who may be expected to behave differently from individuals who remain in their natal parishes. This study uses data from C18-19th parish registers of north-west Germany to estimate the difference in age at marriage between leavers and stayers. The difference is not significant for males; although that for females is significant, it is small and the consequence of failing to include migrants is likely to be negligible for most studies. However, it is shown that there is also an independent effect on age at marriage that is due to the woman's natal social (economic) status; historical demographic studies that ignore this dimension may risk confounding two different effects. [ABSTRACT FROM AUTHOR]

It has been argued that the priority that natural selection places on reproduction negatively affects other processes such as longevity and the problem posed by this trade-off underlies the disposable soma theory for the evolution of human ageing. Here we examine the relationship between reproduction and longevity in a historical human population (the Krummhörn, north-west Germany 1720-1870). In our initial analyses, we found no support for the hypothesized negative effects of reproduction on longevity: married women who remained childless lived no longer than women who reproduced and women who had few children lived no longer than women who had many children. However, more detailed analyses in relation to socio-economic class revealed that the extent to which reproduction has an effect on longevity is a function of the level of economic deprivation. We found that, when possible sources of confound were controlled for (e.g. duration of marriage and amount of time spent in fecund marriage), there is an increasingly strong relationship between longevity and reproduction with increasing poverty.