Life history patterns of new world monkeys

Allometric methods are used to investigate the life history patterns of New World monkeys. These patterns are compared to those found in other haplorhines and links with ecology are explored. The life history characteristics of the cebid monkeys suggest that these species are primarily slow breeding and slow developing for primates of their size. I suggest that these characteristics arose during a long period of adaptation to stable rainforest habitats. The capuchins and squirrel monkeys are a notable exception to the general rule that genera found outside primary forests will have a “fast” life history. In the marmosets and tamarins selection for small size and high birth rate has occurred, probably as a result of their adapting to more secondary habitats. It is this selection for rapid breeding, combined with the preadaptation of paternal care, that has probably led to twinning in these species. The evidence presented indicates that it is unlikely that twinning arose as a direct result of the mechanical constraints of small size but is more probably due to selection for increased reproductive output.