You Can Pick Your Friends But Not Your Relatives

Luis Royo - "People of the Sea"

A recent paper in Science Magazine shows that modern hunter-gatherer communities show a surprising number of unrelated or distantly related people living together, with the average person in a band being genetically related to only about 25% of the other individuals in the band.  This is in contrast to previous anthropological points of view which suggested that hunter-gathers lived mostly with close kin. They conclude that bands are mostly composed of unrelated or distantly related people, and that this arrangement promotes cultural learning, because of the transfer of knowledge between bands of people with the transfer of individuals between bands.  One of the more surprising results was that bands were frequently found to contain brother-sister co-resident groups, unknown in other primates.

The behavior of hunter-gatherers is an important topic, since human beings have spent most of their evolutionary history living in this way, so that the behavior of hunter-gatherers may be considered to represent the behavior of humans in their most "natural" state.

I just prefer to think that people hang around with people they like and can work with, rather than those they are related to.