Cross-Cultural Research on Asymmetric Kin Invenstment

Alexander Pashos works on kinship from the perspective of the evolution of human social behaviour. He is interested in how social and biological mechanisms interact with each other. In his research, he tests predictions derived from evolutionary (a.k.a. sociobiological) theories.

An example is the ‘paternity (un)certainty’ hypothesis, which suggests that people will be more likely to help relatives to whom they are linked through women than those to whom they are linked through men. This is because, according to the theory, what matters for cooperation is the biological connection – which is certain in the case of mother-child links but always open to some doubt in the case of fathers. This may throw light on a commonly found pattern of ‘asymmetric’ grandparental care. There are numerous empirical surveys from Western societies which show that on average children receive more care from the parents of their mother, particularly their maternal grandmother, than from the parents of their father. The ‘paternity uncertainty’ hypothesis would neatly explain this bias – and has found its way into evolutionary textbooks as the likely explanation.

Nevertheless this hypothesis has its weaknesses (Pashos 2017). In an earlier comparative study of grandparental care-giving in Greece and Germany, Pashos found that rural Greeks invested most in the children of their sons. Confidence of paternity may well be high in Greek patrilocal village communities but – since it can never be higher than confidence in maternity – the ‘paternity uncertainty’ hypothesis, if valid, would only explain a more or less strong preference to invest in daughters’ children. It can never explain a greater tendency to favour sons’ children. There must be other reasons for grandparental bias, and this also suggests that paternity uncertainty might not be the only explanation for the matrilateral bias found elsewhere.