Why Is Sex Fun?: The Evolution of Human Sexuality
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Show-offs, men as, 98–100, 102
Siblicide, conflict of interests leading to, 100–101
Signals, 128–46. See also Animal signals; Human signals; Ovulatory signals
Sillén-Tullberg, Birgitta, 77–78, 88
Social systems, evolution and, 11
Somatotropin (growth hormone), 48
Songbirds, sex and parental care and, 69
Sperm: costliness of production of, 67
egg larger than, 21
Spider monkeys, ovulatory signs and, 78
Spiders: male role and, 7
sexual cannibalism and, 7, 11–12
Spontaneous male lactation, 42, 51–52, 60
Spotted Sandpipers: parental care and, 16
sex-role-reversal polyandry and, 26–29, 57
Starvation, lactation in men and recovery from, 51
Steatopygia, 138, 139
Steers, hormones and milk production and, 49
Steroids, 45
Sticklebacks, parental care and, 16, 26
Stumptailed macaques, spontaneous male lactation and, 52
Testes, 45
male pseudohermaphrodites and, 47
testosterone and, 45
Y chromosome and, 44, 45
Testosterone, 45
effects of, 47–48
male pseudohermaphrodites and, 46–47
Therapsid reptiles, lactation and, 58
Tigers, one-night stands and, 5
Toads, parental care and, 16. See also Midwife toads
Tortoises, eggs of, 108
Tre-ba, polyandry and, 36, 37
Truth in advertising theory of signals, 133–35, 136–39
Turtles, aging and, 113
Ultimate explanation, proximate mechanisms versus, 108–9
Unwed mothers, parental care from, 6
Uterus, 45
Vagina, 45
male pseudohermaphrodites and, 47
Vas deferens, 45
Vervets: concealed ovulation and, 74–75, 79
ovulatory signals and, 78
promiscuous mating system of, 78–79
Virgins as brides, confidence in paternity and, 37
Visual signals, 64, 78, 82, 130
Vivipary, 22
Voice change in males, as signal, 127–28
Weaning, in hunter-gatherer societies, 59
Whales. See Baleen whales; Killer whales; Pilot whales
Widowbirds. See Long-Tailed Widowbirds
Wilson’s Phalaropes, sex-role-reversal polyandry and, 16, 26–29, 36, 57
Witch’s milk, 49
Wolffian ducts, 45
Wolves: lack of paternal care and, 2–3
meat provisioning and, 92
parental care and, 54
Women. See Females (human)
X chromosome, 43–44
Y chromosome, 43, 44, 45
male pseudohermaphrodites and, 47
Zahavi, Amotz, 132–33, 144–45
Zahavi’s handicap principle of signals, 132–33, 144–45
Zebras: harems and, 5
paternal care and, 3