Status Updates From Introduction to Evolutionar...

"Since the 1960s, primatologists thought that male and female gibbons mate for life (monogamy). However, recent field studies reveal that some gibbon species have extra-pair copulations (Reichard, 1995). This intriguing finding calls into question theories on monogamy in animals" (73).

"Marmosets live in groups comprising one breeding female, several adult males who mate with this female, and a varying number of non-reproducing females and males. Primatologists found that subordinate (non-reproducing) females in these groups are reproductively suppressed because of their own hormones (Barrett et al., 1990)! When the researchers isolated subordinate females, the monkeys began to ovulate" (70).

"... male muriquis (Brachyteles arachnoides) will diffuse tension by cuddling while hanging upside down by their tails (Strier, 1999)!" (69).