Another classification involves two tribes, Panini and Homini. Both Pan and Gorilla genera are divisions in the Panini tribe, while Homini tribe includes Homo sapiens. Homo sapiens, better known as human beings belong to the Hominidae family and the Homo genus. Hylobates, Pongo pygmaecus, Pan paniscus, Pan troglodytes, Gorilla gorilla and Homo sapiens are the six different species of Homonoids.
Chimpanzees belong to the Pan genus. They spend a considerable amount of time on the ground and inhabit in large complex social groupings. They are specially adapted for knuckle walking. They also indulge in hunting as a group, sharing of food and tool making. They resemble our ancestors in anatomy as well as social behavior and are considered to be our closest living cousins. Orangutans belong to the Pongo genus. They are generalized climbers and are most isolated among the primates. Gorillas are the largest among primates. The male gorilla is larger and stronger than its female counterpart. The male gorilla has exclusive relationships with a group of females and keeps away male rivals from this group.
The Old World species exhibit sexual dimorphism as a result of polygynous mating system. Hence, the males are bigger and stronger than the females to attract and sustain the pressure of defending multiple mates.