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Pseudohermaphrodites

Pubic hair, sexual maturity in humans indicated by

Public sex, mammals and

Pygmy chimpanzees. See Bonobos

Pythons, parental care and

Rabbits, duration of fertility of

Rats (male), mammary glands and

Recreational sex; coparenting and; extramarital sex and; sex-to-promote-family-values theory and. See also Concealed ovulation; Sexual receptivity (female)

Rennell Island, consumption of fruits and seeds by birds and

Repair and maintenance; death and accidents and; reproduction versus

Repair and reproduction, natural selection and

Reproductive strategy

Reptiles: therapsid; vivipary and

Rhesus macaques, duration of fertility of

Rockefeller, Nelson

Runaway selection model. See Fisher’s runaway selection model of signals

Saddleback tamarin monkeys, paternal care and

Salmon, big-bang reproduction (semelparity) and

San (Bushmen): fat in women of; men as hunters and

Sandpipers. See Spotted Sandpipers

Scrotum

Sea birds, pair bonds and

Seahorses: male pregnancy and; parental care and

Seals. See Arctic seals

Secondary female, polygyny in Pied Flycatchers and

Semelparity. See Big-bang reproduction

Seminal vesicles

Senescence. See Aging

Sequential monogamy, humans and

Sex appeal; extramarital sex and; as signal

Sex chromosomes

Sex differences, hormones and

Sex for fertilization. See Fertilization, mammals having sex for

Sex for fun. See Recreational sex

Sex in private, humans and

Sex in public, mammals and

Sex-role-reversal polyandry

Sex-to-promote-family-values theory, of recreational sex

Sexual cannibalism

Sexual evolution

Sexual maturity, signals indicating

Sexual ornamentation: function of; in men; in women

Sexual receptivity (female); better-genes-through-cuckoldry theory of; coparenting and; daddy-at-home theory and; extramarital sex and; infanticide and; many-fathers theory and

Sexual signals. See Signals

Shore birds, sex-role-reversal polyandry and

Show-offs, men as

Siblicide, conflict of interests leading to

Signals. See also Animal signals; Human signals; Ovulatory signals

Sillén-Tullberg, Birgitta

Social systems, evolution and

Somatotropin (growth hormone)

Songbirds, sex and parental care and

Sperm: costliness of production of; egg larger than

Spider monkeys, ovulatory signs and

Spiders: male role and; sexual cannibalism and

Spontaneous male lactation

Spotted Sandpipers: parental care and; sex-role-reversal polyandry and

Starvation, lactation in men and recovery from

Steatopygia

Steers, hormones and milk production and

Steroids

Sticklebacks, parental care and

Stumptailed macaques, spontaneous male lactation and

Testes; male pseudohermaphrodites and; testosterone and; Y chromosome and

Testosterone; effects of; male pseudohermaphrodites and

Therapsid reptiles, lactation and

Tigers, one-night stands and

Toads, parental care and. See also Midwife toads

Tortoises, eggs of

Tre-ba, polyandry and

Truth in advertising theory of signals

Turtles, aging and

Ultimate explanation, proximate mechanisms versus

Unwed mothers, parental care from

Uterus

Vagina; male pseudohermaphrodites and

Vas deferens

Vervets: concealed ovulation and; ovulatory signals and; promiscuous mating system of

Virgins as brides, confidence in paternity and

Visual signals

Vivipary

Voice change in males, as signal

Weaning, in hunter-gatherer societies

Whales. See Baleen whales; Killer whales; Pilot whales

Widowbirds. See Long-Tailed Widowbirds

Wilson’s Phalaropes, sex-role-reversal polyandry and

Witch’s milk

Wolffian ducts

Wolves: lack of paternal care and; meat provisioning and; parental care and

Women. See Females (human)

X chromosome

Y chromosome; male pseudohermaphrodites and

Zahavi, Amotz

Zahavi’s handicap principle of signals

Zebras: harems and; paternal care and

concealed ovulation for that purpose, she then used it to pick a good caveman, to entice or force him to stay at home with her, and to get him to provide lots of protection or help for her baby—secure in the knowledge that it was his baby too.

On reflection,