lsquo Fatherless rsquo Immatures Immatures had similar

Harcourt et?al., 1981, Leutenegger and Kelly, 1977 and Plavcan and van Schaik, 1997). The association between these traits and group structure is very strong, making it highly unlikely that gorillas arrived at the combination of extreme sexual dimorphism, well-developed weaponry and small testes size–body ratio via some other route. However, it is easy to conceive of this morphology developing despite a persistent minority of two-male or three-male groups with high reproductive skew, typically (although not always) made up of related males.