Figure 1.

A diagram showing how asymmetries of relatedness can occur through multiple paternity of a female's offspring, and in a simple matrilineal society with sex-biased dispersal. (a) With multiple paternity either within a brood or, as is more likely, across a female's reproductive lifetime, offspring from the same mother differ in their relatedness owing to the presence of different paternal genomes. (b) Schematic of a simple matrilineal society as described in the text. Males, coming in from outside the group, hold short breeding tenure (matings with females are indicated by thin arrows). Male offspring (not shown) leave the group when sexually mature. What can be seen is that all females share, to differing degrees, maternally derived genes (in red)—this would of course also be true for male offspring. However, paternally derived genes are only present in the strata of the social group and are not shared as widely.