Fictive Kinship - Use in Sociobiology

Use in Sociobiology

In the biological and animal behavioural sciences, the term 'kinship' has a different meaning from the current anthropological usage of the term, and more in common with the former anthropological usage that assumed that blood ties are ontologically prior to social ties. In these sciences, 'kinship' is commonly used as a short hand for 'the regression coefficient of (genetic) relatedness', which is a metric denoting the proportion of shared genetic material between any two individuals relative to average degrees of genetic variance in the population under study. This coefficient of relationship is an important component of the theory of inclusive fitness, a treatment of the evolutionary selective pressures on the emergence of certain forms of social behavior. Confusingly, inclusive fitness theory is more popularly known through its narrower form, kin selection theory, whose name clearly resonates with former conceptions of 'kinship' in anthropology.

Whilst inclusive fitness theory thus describes one of the necessary conditions for the evolutionary emergence of social behaviors, the details of the proximate conditions mediating the expression of social bonding and cooperation have been less investigated in sociobiology. In particular, the question of whether genetic relatedness (or 'blood ties') must necessarily be present for social bonding and cooperation to be expressed has been the source of much confusion, partly due to thought experiments in Hamilton's early theoretical treatments (see kin selection). As well as setting out the details of the evolutionary selection pressure, Hamilton also roughly outlined two possible mechanism whereby the expression of social behaviors might be mediated:

The selective advantage which makes behaviour conditional in the right sense on the discrimination of factors which correlate with the relationship of the individual concerned is therefore obvious. It may be, for instance, that in respect of a certain social action performed towards neighbours indiscriminately, an individual is only just breaking even in terms of inclusive fitness. If he could learn to recognise those of his neighbours who really were close relatives and could devote his beneficial actions to them alone an advantage to inclusive fitness would at once appear. Thus a mutation causing such discriminatory behaviour itself benefits inclusive fitness and would be selected. In fact, the individual may not need to perform any discrimination so sophisticated as we suggest here; a difference in the generosity of his behaviour according to whether the situations evoking it were encountered near to, or far from, his own home might occasion an advantage of a similar kind.” (1996, 51)

Traditional sociobiology did not consider the divergent consequences between these basic possibilities for the expression of social behavior and instead assumed that the expression operates in the 'recognition' manner, whereby individuals are behaviorally primed to discriminate which others are their 'true' genetic relatives, and engage in cooperative behavior with them. But when expression has evolved to be primarily location-based or context-based, depending on a society's particular demographics and history, social ties and cooperation may or may not coincide with 'blood ties'. Reviews of the mammal, primate and human evidence demonstrate that expression of social behaviors in these species are primarily location-based and context-based (see Nurture kinship), and examples of what used to be labeled as 'fictive kinship' are readily understood in this perspective.