主题：【原创】飞天鸭看人类文明史：原始社会好（中） -- 酥油茶

Mating occurs throughout the year and there is no evidence of a birth season, female chimpanzees do exhibit seasonality in the number of estrous females within a group (Wallis 1995; Boesch &Boesch-Achermann 2000; Wallis 2002). The number of estrous females is positively related to food abundance; because of the energetic requirements of ovulation and mating, female chimpanzees are more likely to come into estrus during times when food is readily available (Anderson et al. 2006). The majority of chimpanzee reproductive behavior is promiscuous, with females mating with multiple males opportunistically during estrus, though the majority of copulation occurs during the 10-day period of maximal tumescence (Goodall 1986). There are other types of reproductive strategies that are recognized as well. Restrictive mating, where the dominant male restricts other males from mating with estrous females in the community, consortship mating, where an adult pair leave the community for several days to weeks, and extra-group mating, where females leave their communities and mate furtively with males from nearby communities (Goodall 1986; Gagneux et al. 1999). Chimpanzee social and mating groups do not always overlap, given the variety of reproductive situations. This may have evolved because females have limited choice in mates after committing to a community, and the dominance hierarchy of males often dictates which males an estrous female will mate with. By having multiple strategies, females can expand the pool of males from which they choose while not losing the important support of the males in their communities (Gagneux et al. 1999). Having multiple strategies also maximizes the chances of males' reproductive success; they are able to vary, throughout their lives, their mating strategies with depending on their position in the dominance hierarchy.

Polygyny may have reappeared to some extent with the evolution of Homo sapiens sapiens 40,000 B.P., but perhaps not until 15,000–11,000 B.P. did disparity in resources controlled by males allow some males to exceed the polygyny threshold.