  On one hand, kinship is a universal human phenomenon that tends to align with
biological relatedness, which might suggest evolutionary foundations. On the
other hand, kinship has exceptional variation across the human populations,
which points to cultural foundations. Furthermore, even if its foundation was
biological, kinship is often too imprecise to track genetic relatedness
efficiently, while inclusive fitness theory would suggest focusing only on the
closest relatives, which is not the case in most human cultures. It was the
parallel validity of these contradicting arguments that led to decades of
fierce debate about the definition and measurement of the phenomenon. This
paper offers a new approach to kinship. First, the model demonstrates that it
is possible to generate kinship networks (a) derived from the kind of basic kin
connections that our species shares with other apes, but (b) driven by network
rather than biological logic beyond the immediate family. Second the model
demonstrates that kinship as a network heuristic works efficiently only in high
fertility societies, and gives way to similarity-based friendship with
demographic transition. The results explain (i) why kinship labelling is unique
to our species, (ii) why kinship is universal among human cultures, (iii) why
kinship terminology systems are varied across cultures, (iv) why linguistic kin
assignment is imprecise, and (v) why kinship is replaced by homophily when
relatives are scarce. The model offers a unifying framework to the debate
between social and evolutionary anthropology concerning the concept of human
kinship.
