Origin and evolution of primate social organisation: a reconstruction

Area of Science:

• Primate Social Evolution
• Mammalian Social Organization
• Behavioral Ecology

Background:

• Primate social organization research often assumes a primitive solitary foraging system for nocturnal prosimians.
• This 'solitary' label oversimplifies diverse social networks within nocturnal prosimian species.
• Previous classifications lack the granularity to link social patterns with ecological or phylogenetic variables.

Purpose of the Study:

• To establish a classification system for non-gregarious mammal social organization based on spatial relations and sociality.
• To re-evaluate the ancestral social organization pattern of primates.
• To investigate the evolutionary origins of social structures in nocturnal prosimians and other mammals.

Main Methods:

• Review of existing literature on primate and non-primate social organization.
• Analysis of new field data on cheirogaleids (mouse and dwarf lemurs).
• Comparative analysis of social systems across strepsirhines, placentals, marsupials, and monotremes.

Main Results:

• Nocturnal prosimians exhibit diverse social networks, including dispersed multi-male systems and dispersed monogamy, not a uniform dispersed harem system.
• The dispersed harem system is refuted as the ancestral primate social organization.
• Promiscuity is proposed as the ancestral mammalian social organization, with dispersed multi-male systems derived from it as the ancestral primate condition.
• Gregarious social patterns in Aotus, Avahi, and Tarsius likely evolved from diurnal primate ancestors, suggesting Avahi is secondarily nocturnal.

Conclusions:

• The ancestral primate social organization is likely a dispersed multi-male system, evolving from mammalian promiscuity.
• Existing classifications of nocturnal prosimian sociality are inadequate and require revision.
• Understanding diverse social networks is crucial for reconstructing primate evolutionary history.