Figure 36.4 Summary of the principal factors, and their interrelationships, thought to be important in the evolution of
cooperative breeding and eusociality in the Bathyergidae. (Modified from J. U. M. Jarvis, unpubl.; Brett 1986 and Spinks
1998).a prerequisite and may be a derived trait. Phylogenetically
constrained factors such as long gestation and developmen-
tal time may also play a role. Comparative endocrine stud-
ies of African mole-rats suggest that the frequency and
mode of dispersal and nascent colony formation, which in
turn are influenced by ecological factors, may be funda-
mental in shaping sociality and the proximate mechanisms
controlling the reproductive skew so characteristic of mole-
rats. New data on group kin structure and parentage high-
light the potential diversity in reproductive success among
males, and suggest that combinations of dominant control,
self-restraint (arising from incest avoidance), and possibly
other models of reproductive suppression operate within
colonies. The recent characterization of several new social
species and the accumulating molecular genetic data offer
the opportunity for further, more extensive and detailed
comparative studies within the family.African Mole-Rats: Social and Ecological Diversity 437