Aché Indians, hunting by men of, 93–98
Adoptive mothers, lactation by, 51
Adultery laws, confidence in paternity and, 37–38. See also Extramarital sex
African elephants, menopause and, 125
African hunting dogs: infanticide and, 73
meat provisioning and, 92
Aging, 109–10
accidents and bad conditions and, 113–14
animal signals indicating, 130
human signals indicating, 135, 142
kingpin principle of, 114–16
repair and maintenance and, 109–13
repair and reproduction and, 112–13
signals indicating, 130, 135, 142
Albatrosses: “divorce” rates and, 135
eggs of, 108
parental care and, 17
Alligators, parental care and, 23
American men, role of, 101–2
Amphibians: external fertilization and, 21
parental care and, 16
vivipary and, 22
Anatomical adaptations, natural selection and, 10–13
Andaman Islands, fat in women of, 138
Andelman, Sandy, 74–75
Androgens, 45
male pseudohermaphrodites and, 47
Animal signals, 128–34
age indicated by, 130
auditory, 129
behavioral, 129
electrical, 129
experimental study of, 130–31
Fisher’s runaway selection model of, 131–32
gender indicated by, 130
male sexual ornamentation and, 140
natural selection and, 128–29
olfactory, 129
sexual maturity indicated by, 130
truth in advertising theory of, 133–34
Zahavi’s handicap principle of, 132–33
Antelope, mating systems of, 7
Anticontraceptive theory, of concealed ovulation, 70–71
Ants, signals and, 129
Apes: aging and, 113–14
humans compared to, 8–10
ovulatory signs and, 78
penis of, 144
promiscuous mating system of, 82, 83
sexual distinctiveness and, 47–48. See also Bonobos; Chimpanzees; Gibbons; Gorillas; Orangutans
Archaeopteryx, 57
Arctic Indian men, hunting by, 95
Arctic seals, lactation and, 59
Asian elephants, menopause and, 125
Auditory signals, 129
Axillary hair, sexual maturity in humans indicated by, 135, 142
Baboons: ovulatory signals and, 64, 78, 82, 130
sex confined to estrus and, 64
Baleen whales, eggs of, 108
Bandicoots, pregnancy and, 58
Barbary macaques: public sex and, 3
sex confined to estrus and, 64–65
Bats, mating systems of, 7. See also Dyak fruit bats; Hammer-headed fruit bats
Battle of the sexes. See under Parental care
Better-genes-through-cuckoldry theory, of female sexual receptivity, 70
Big-bang reproduction (semelparity), 7, 106–7
Birds: coparenting and, 29–34, 56
evolutionary commitment of, 55–58
internal fertilization and, 22, 55–56
mating systems of, 7
pair bonds formed by, 7–8
parental care and, 7, 16, 17, 55–58, 69
on Rennell Island, 122–23
sex for fertilization and, 66–67
sex-role-reversal polyandry and, 16, 26–29, 36, 57
Body fat. See Fat
Body signals. See Signals
Bonobos (pygmy chimpanzees): humans compared to, 8, 9
menopause and, 125
promiscuous mating system of, 8, 9, 69, 78–79
sex for fun and, 3
Bowerbirds, golden crest of, 132, 137
Breast-feeding. See under Lactation
Breasts: hormones and development of, 47–50
as signal in human females, 135, 136, 138–39, 141
Bride prices: confidence in paternity and, 37
women’s desirability and, 141
Brown, James, 133–34
Brush turkeys, parental care and, 17
Buttocks, as signal in human females, 138, 139
Century plants, big-bang reproduction and, 107
Chaperoning, confidence in paternity and, 38
Chickens, large eggs of, 27
Childbirth, risk of mother’s death and, 117–18
Child care. See under Parental care
Chimpanzees, 13
infanticide and, 73
lack of paternal care and, 2–3
menopause and, 125
ovulatory signals and, 78, 80, 81, 82
penis of, 144
private sex (consortship) and, 3
promiscuous mating system of, 9, 69, 78–79, 82, 83
public sex and, 3
pygmy, see Bonobos
Chromosomes, 43–44
Circumcision, female. See Clitoridectomy
Clitoridectomy, confidence in paternity and, 38
Clitoris, 45
Comparative method, concealed ovulation studied by, 77–88
Concealed ovulation, 5, 64, 67, 68–88
anticontraceptive theory of, 70–71
comparative method studying, 77–88
daddy-at-home theory of, 71–73, 75–76, 79, 84, 86–87
detecting ovulation and, 63–64
evolution of, 80–88
female receptivity and, 64–65
hormonal test kit and, 63–64
many-fathers theory of, 71, 73–75, 76, 79, 84
mating systems and, 79–80
paternity confused by, 71, 73–75
prostitution theory of, 70
theories explaining, 70–88
Confessions of Felix Krull, Confidence Man (Mann), 88
Confidence of parenthood: concealed ovulation and, 74–75
daddy-at-home theory of concealed ovulation and, 71–73, 75–76
genetic testing and, 60–61, 76
many-fathers theory of concealed ovulation and, 71, 73–75, 76
parental care and, 20, 24–25, 30, 37–38, 56
Conflict of interests: between closely related people, 100–101
in hunter-gatherer societies, 100
Consortship, chimpanzees and, 3
Coparenting: birds and, 29–34, 56
daddy-at-home theory and, 72
male lactation and, 53–54
sexual receptivity and, 68–70
Couples, humans forming, 4, 5–6
Cows, hormones and lactation and, 48
virgin cows and, 49
Daddy-at-home theory, of concealed ovulation, 71–73, 75–76, 79, 84, 86–87
Darwin, Charles, 10
Deer, antlers of, 133–34
Dihydrotestosterone, 45
male pseudohermaphrodites and, 47
Dinosaurs, 57
Divorce, 102
human signals and, 135
Dogs: mammary glands and, 48
sex for fertilization and, 66
signals and, 129. See also African hunting dogs
Dolphins, sex for fun and, 3
Dyak fruit bats, spontaneous male lactation and, 52, 54, 60
Echidnas, internal fertilization and, 22
Eggs: larger than sperm, 21
menopause and depletion of, 107–9, 115
Electrical signals, 129
Electric fishes, signals and, 129
Elephants: eggs of, 108
menopause and, 125
pregnancy and, 58
Enzymes, male/female organ development and, 46
Epididymis, 45
Estrogen, lactation and, 49–50
Estrus, mammals confining sex to, 64–65. See also Fertilization, mammals having sex for
Evolution: of concealed ovulation, 80–88
human sexuality and, 10–13. See also Natural selection
Evolutionary commitment, 54–55
birds’ reproductive strategy and, 55–58
mammalian reproductive strategy and, 58–60, 62
External fertilization, 21
alternative opportunities foreclosed by child care and, 23
in fish, 13
humans and, 61
obligate parental investment and, 21
parental care and, 25–26
Extramarital sex, 5
biological significance of, 98–99
confidence of parenthood and, 76
hunting and, 98–100
recreational sex and, 69–70
as risky, 68
sex appeal and, 141
sex differences in attitudes toward, 38–39
Extra-pair copulations, of Pied Flycatchers, 33–34
Facial beauty, as human signal, 137–38
Fallopian tubes, 45
Fat, as signal in human females, 135, 138–39, 141
Female menopause. See Menopause
Females (human): breasts and, 135, 136, 138–39, 141
extramarital sex and, 38–39
facial beauty and, 137–38, 141
fertility decline in, 103, see also Menopause
hormones and breast development and, 49–50
lactation by, 23, 24, 35–36, 49–50
parental care and, 4, 21–24, 25, 29–30, 35–38, 102
plant foods gathered by, 91, 93–94, 95, 100
sexual maturity of, 142
sexual ornamentation and, 138–41. See also Concealed ovulation; Lactation; Menopause; Sexual receptivity (female)
Females (mammalian): duration of fertility of, 105–6, 115
parental care and, 7, 15–16, 21–34, 55–57
sex-role-reversal polyandry and, 26–29
Fertilization, mammals having sex for, 3, 64–65, 66–67. See also External fertilization; Internal fertilization
Fish: external fertilization and, 13, 21
male role and, 7
mating systems of, 7
parental care and, 7, 16, 25–26
vivipary and, 22
Fisher, Ronald, Sir, 131–32, 144
Fisher’s runaway selection model of signals, 131–32, 144
Flycatchers. See Pied Flycatchers
Ford, Henry, 114–15
Foreclosed opportunity, parental care and, 20, 23–24, 35–37, 38, 56
Frogs: mating systems of, 7
Fun, sex for. See Recreational sex
males passing to offspring, 24. See also Chromosomes; Natural selection
Genetic testing, confidence of parenthood and, 60–61
Gibbons: couples and, 4
paternal care and, 3
sex confined to estrus and, 65
sexual distinctiveness and, 48
Glans penis, 45
Glass frogs, parental care and, 26
Goats (female), lactation in virgin: hormones and, 49
“milking” and, 50
Goats (male), lactation and: hormones and, 49
spontaneous lactation and, 42, 51–52
Gorillas: harems and, 5, 78, 82
head shape indicating sex and, 130
humans compared to, 9
ovulatory signals and, 78, 80, 81
paternal care and, 3
sex and parental care and, 69
sexual distinctiveness and, 48
sexuality of, 9
sexual maturity indicated and, 130
Grandmothers, extended role of, 119–20
Great apes. See Apes
Great Tits, breast stripe as signal and, 130–31
Growth hormone. See Somatotropin
Guinea pigs, lactation and, 59
hormones and male lactation and, 49
Hadza, foraging by women of different ages and, 119–20
Hammer-headed fruit bats, lek mating system of, 7, 8
Hamsters, duration of fertility of, 115
Handicap principle. See Zahavi’s handicap principle of signals
Harems: concealed ovulation and, 84, 85
mammals and, 5
primates and, 78, 79, 80, 82, 83
Hawkes, Kristen, 93–98, 119–20
Hazda Indians, hunting by men of, 93, 95–96
Head shape, gender indicated by, 130
Herring Gulls, signals and, 130
Hill, Kim, 93
Hoofed mammals, lack of paternal care and, 2
Hormones: lactation and, 48–50
male lactation and, 47–50
sex differences and, 47–49
Howler monkeys, concealed ovulation and, 82
Human sexuality: apes compared to, 8–10
apparent inefficiency of, 67–68
continuous practice of sex and, see Sexual receptivity (female)
evolutionary biology and, 10–13
extramarital sex and, 5, 38–39, 68, 69–70
internal fertilization and, 21–23
long-term sexual partnerships and, 4, 5–6
mammalian sexuality compared to, 1–10
ovulatory signals and, see Concealed ovulation; polyandry and, 6
premarital sex and, 5
private sex and, 4
proximity to sexual partnerships of others and, 4
sequential monogamy and, 6. See also Concealed ovulation; Females (human); Males (human); Menopause; Parental care (human); Recreational sex; Sexual receptivity (female)
handicap principle of, 133, 144–45
male voice, 127–28
natural selection and, 128–29
penis, 142–46
runaway selection model of, 131–32, 144
sexual maturity, 128–29, 135, 142
sexual ornamentation, 138–41, 142–46
truth in advertising principle of, 133–35, 136–39
women’s breasts, 136, 138–39, 141
Hunter-gatherers: conflict of interests and, 100
lactational amenorrhea and, 36
weaning and, 59
women and, 91, 93–94, 95, 100. See also Hunters, men as
Hunters, men as, 91–101
Aché Indians and, 93–98
extramarital sex and, 98–100
meat provisioning and, 91–93
as show-offs, 98–100
women’s jobs versus, 91, 93–94, 95, 100
Hurtado, A. Magdalena, 93
Hutterite women, babies produced by, 103
Imprisonment of women, confidence in paternity and, 38
Infanticide: conflict of interests leading to, 100–101
many-fathers theory and, 73–75, 76
Infibulation, confidence in paternity and, 38
Insects, mating systems of, 7
Interior vagina, 45
Internal fertilization, 13
alternative opportunities foreclosed by child care and, 23–24
confidence of parenthood and, 25
evolutionary commitment of mammals to, 58–60
obligate parental investment and, 21–23
Inuit (Eskimo) men, hunting by, 95
Investment in young: external fertilization and, 61
male lactation and, 43
parental care and, 20–23, 35, 38, 56
Ismail the Bloodthirsty, Emperor of Morocco, 37
Jacanas (lily-trotters), sex-role-reversal polyandry and, 26–29, 57
Jackrabbits, lactation and, 59
Jones, Nicholas Blurton, 93
Jost, Alfred, 44
Kangaroos, parental care and, 17
Kaplan, H., 93
Ketengban tribe, phallocarps in, 142–43
Killer whales, menopause and, 125
Kingpin principle, aging and, 114–16
Kodric-Brown, Astrid, 133–34
Labia majora, 45
Labia minora, 45
Lactational amenorrhea, 36
evolutionary commitment to, 58–60, 62
hormones and, 48–50
humans and, 23, 24, 35–36, 49–50
infanticide terminating, 73
mammary gland development and, 48
nipple stimulation and, 50–51
origin of, 58
pregnancy and, 58
species differences and, 59
weaning and, 59. See also Lactation (male)
Lactation (male), 41–62
advantages of, 61–62
conditions favoring, 60–61
evolutionary commitment and, 58–60
hormones and, 48–50
male roles and, 53–54
nipple stimulation and, 50
physiological feasibility of, 43–52
pregnancy necessity and, 42, 49
psychological obstacles to, 62
spontaneous lactation and, 42, 51–52, 60
starvation recovery and, 51
technological possibility of, 61–62
Langur monkeys, concealed ovulation and, 79
Lek mating system, of hammer-headed fruit bats, 7, 8
Life span, female reproduction and, 105
Lily-trotters. See Jacanas
Lions: infanticide and, 73
Long-Tailed Widowbirds, tails as signal and, 130, 132
Macaques, ovulatory signals and, 82. See also Barbary macaques; Rhesus macaques; Stumptailed macaques
Male lactation. See Lactation (male)
Male pseudohermaphrodites, 46–47
Males (human): American men, 101–2
divorce and, 102
duration of fertility of, 103, 115
facial beauty and, 137–38
mammary gland development and, 48–50, see also Lactation (male)
menopause and, 5
parental care and, 4, 6, 15, 16, 19, 21, 22, 24, 25, 29–30, 35–38, 71–73, 75, 102
penis of, 142–46
role of, 89–102
sexual maturity of, 128–29, 135, 142
sexual ornamentation and, 140, 142–46
voice change and, 127–28. See also Extramarital sex; Hunters, men as; Lactation (male)
Males (mammalian): duration of fertility of, 103, 105–6, 115
infanticide and, 73–74
mammary gland development and, 48, see also Lactation (male)
meat provisioning and, 92
menopause and, 106–7
parental care and, 2–3, 7, 15, 21, 24, 25–34, 55–58
post copulatory desertion and, 23–25
sex-role-reversal polyandry and, 26–29
signals and, 130, 131–34, 140. See also Lactation (male)
Mammalian sexuality, 2–4
fertility time span and, 4
for fertilization, 3, 64–65, 66–67
harems and, 5, 78, 79, 80, 82, 83
human sexuality compared to, 1–10
mating systems, 7–8
menopause and, 4
one-night stands and, 5
public sex and, 3. See also Females (mammalian); Internal fertilization; Males (mammalian); Parental care (mammalian)
Mammary gland development, hormones and, 47–50. See also Breasts; under Lactation
Mann, Thomas, 88
Mantises, sexual cannibalism and, 7, 11–12
Many fathers theory, of concealed ovulation, 71, 73–75, 76, 79, 84
Marmosets: as monogamous, 78
ovulatory signals and, 78
parental care and, 54
Marriage, by humans, 4
Marsupial mice, 8
menopause in males of, 106–7
sex for fertilization and, 66
Marsupials: internal fertilization and, 13
lactation and, 50, 58. See also Kangaroos
Mating systems: concealed ovulation and, 79–80
evolutionary changes and, 80–88
Men. See under Male
aging and, 109–13
burden of parental dependence of child and, 116–17
costs and benefits of, 116–20
definition of, 4
depletion and aging of egg supply and, 107–9, 115
extended role of postmenopausal women and, 118–20
importance to society of memories of old women and, 120–24
increase in expected life span and, 104–5
kingpin principle and, 114–16
in mammals, 106–7
more children produced by, 116–25
risk of death in childbirth and, 117–18
risks in infants of older mothers and, 118
Menstrual cycle, lactational amenorrhea and, 36. See also Menopause
Mice: aging and, 113
duration of fertility of, 106, 115
mammary glands in male, 48
repair versus reproduction and, 112–13. See also Marsupial mice
Midwife toads, parental care and, 16, 26
Missing Link, in concealed ovulation evolution, 80–88
Mixed reproductive strategy, of Pied Flycatchers, 33, 34
Møller, Anders, 77–88
Monkeys: concealed ovulation and, 82
monogamy and, 82
promiscuous mating system of, 82, 83. See also Night monkeys; Spider monkeys
Monogamy: concealed ovulation and, 79–81, 84–86
daddy-at-home theory and, 71–73, 75
Monotremes: internal fertilization and, 22
lactation and, 58
Mormons, polygyny and, 37
Mullerian ducts, 45
Mullerian inhibiting hormone, 45
male pseudohermaphrodites and, 47
Muscles, as signal in human males, 135, 136–37
Napoleon the Third, 67
Natural selection, 104
behavior and, 16
concealed ovulation and, 87
lactation and, 60
male lactation and, 61
menopause and, 104
parental care and, 16–18
repair and reproduction and, 109–13
sexuality and, 10–13
signals and, 128–29
vertebrate limbs and, 87
New Guinea: bride prices in, 141
phallocarps in, 142–43
Night monkeys, concealed ovulation and, 79
Nizam of Hyderabad, 37
Nursing. See under Lactation
O’Connell, James, 93
Octopus, big-bang reproduction (semelparity) and, 7
Offspring, conflict of interest between parents and, 100–101
One-night stands, 5
On the Origin of Species (Darwin), 10
Opportunity. See Foreclosed opportunity
Orangutans: concealed ovulation and, 82
head shape indicating sex and, 130
humans compared to, 9
one-night stands and, 5
ovulatory signs and, 78
sexuality of, 9
Oring, Lewis, 27
Ostriches, parental care and, 17
Ovaries, 44
evolutionary changes in, 80–88
in mammalian sexuality, 64, 77–78
in primates, 64, 77–78, 82, 130. See also Concealed ovulation
Parental care, 15–39
alternative opportunities foreclosed by child care and, 20, 23–24, 35–37, 38
battle of the sexes and, 18–20
confidence of parenthood and, 20, 24–25, 37–38, 38
male lactation and, 53–54
sex differences in obligate parental investment and, 20–23, 35, 38
Parental care (human), 2, 4, 6, 15, 34–38
alternative opportunities foreclosed by child care and, 23–24, 35–37
battle of the sexes and, 18–20
burden of long period of, 116–17
confidence of parenthood and, 24–25, 37–38
conflict of interests and, 100–101
females and, 4, 21–24, 25, 29–30, 35–38, 102
males and, 4, 6, 15, 16, 19, 21, 22, 24, 25, 29–30, 35–38, 71–73, 75, 102
polygyny and, 37
recreational sex and, 68–70
sex differences in obligate parental investment and, 21–23, 35
unwed mothers and, 6
Parental care (mammalian), 2–3, 7, 13, 15–34
alternative opportunities foreclosed by child care and, 23–24, 56
battle of the sexes and, 18–20
choices in, 16–18
confidence of parenthood and, 24–25, 56
females and, 7, 15–16, 21–34, 55–57
lactation and, 53–54
male post-copulatory desertion and, 23–25
males and, 2–3, 7, 15, 21, 24, 25–34, 55–58
natural selection and, 16–18
sex and, 69
sex differences in obligate parental investment and, 22, 56
sex-role-reversal polyandry and, 26–29
Parenthood, confidence of. See Confidence of parenthood
Parricide, conflict of interests leading to, 100–101
Paternal care, 2–3. See also under Male
Peacocks, 8
tail of, 132
Penis, 44
internal fertilization and, 21
as signal in human males, 142–46
Penis shaft, 45
Phalaropes. See Wilson’s Phalaropes
Phallocarps, 143–44
Pheromones, 77
Pied Flycatchers: coparenthood and, 30–34
sex for fertilization and, 66–67
Pigeons: lactation and, 42, 56
small eggs of, 27
Pilot whales, menopause and, 107, 124–25
Placentals, lactation and, 48, 58
Platypus, internal fertilization and, 22
Plummage, as signal, 130
Polyandry, 36
humans and, 6
sex-role-reversal, 26–29, 36, 57
Polygamy, harems and, 6
Polygyny: coparenthood in Pied Flycatchers and, 30–34
Porcupines, aging and, 113
Post-copulatory desertion by males, 23–25
exceptions to, 25–34
Pregnancy: duration of, 58
Premarital sex, humans and, 5
Primary female, polygyny in Pied Flycatchers and, 30–31, 32
Primates: concealed ovulation studied with, 77–88
family tree of, 80–88
mammary glands and, 48
mating systems of, 78–79, 80–88
ovulatory signals and, 64, 77–78, 82, 130
promiscuity of, 78–79, 80, 82, 83. See also specific primates, i.e. Apes; Baboons; Chimpanzees, etc.
Private sex, humans and, 4
Progesterone, lactation and, 49–50
Prolactin, lactation and, 48, 49
Promiscuity: concealed ovulation and, 84, 85
of humans, 79
of primates, 78–79, 80, 82, 83
Prostate gland, 44
Prostitution theory, of concealed ovulation, 70
Providers, men as, 98–99, 100, 102
Proximate mechanism, ultimate explanations versus, 108–9
Pseudohermaphrodites, 46–47
Pubic hair, sexual maturity in humans indicated by, 135, 142
Public sex, mammals and, 3
Pygmy chimpanzees. See Bonobos
Pythons, parental care and, 23
Rabbits, duration of fertility of, 115
Rats (male), mammary glands and, 48
Recreational sex, 4, 5, 10, 66, 67
coparenting and, 68–70
extramarital sex and, 69–70
sex-to-promote-family-values theory and, 68–69. See also Concealed ovulation; Sexual receptivity (female)
Rennell Island, consumption of fruits and seeds by birds and, 122–23
Repair and maintenance, 109–13
death and accidents and, 113
reproduction versus, 112–13
Repair and reproduction, natural selection and, 109–13
Reproductive strategy, 17
Reptiles: therapsid, 58
vivipary and, 22
Rhesus macaques, duration of fertility of, 106, 115
Rockefeller, Nelson, 67
Runaway selection model. See Fisher’s runaway selection model of signals
Saddleback tamarin monkeys, paternal care and, 3
Salmon, big-bang reproduction (semelparity) and, 7, 107
San (Bushmen): fat in women of, 138
men as hunters and, 95
Sandpipers. See Spotted Sandpipers
Scrotum, 45
Sea birds, pair bonds and, 8
Seahorses: male pregnancy and, 42
parental care and, 16
Seals. See Arctic seals
Secondary female, polygyny in Pied Flycatchers and, 31–32
Semelparity. See Big-bang reproduction
Seminal vesicles, 45
Senescence. See Aging
Sequential monogamy, humans and, 6
Sex appeal, 135
extramarital sex and, 141
Sex chromosomes, 43–44, 45, 47
Sex differences, hormones and, 47–49
Sex for fertilization. See Fertilization, mammals having sex for
Sex for fun. See Recreational sex
Sex in private, humans and, 4
Sex in public, mammals and, 3
Sex-role-reversal polyandry, 26–29, 36, 57
Sex-to-promote-family-values theory, of recreational sex, 68–69
Sexual evolution, 11–13
Sexual maturity, signals indicating, 128–29, 130, 135, 142
Sexual ornamentation: function of, 145
in women, 138–41
Sexual receptivity (female), 5, 64–65, 67
better-genes-through-cuckoldry theory of, 70
coparenting and, 68–70
daddy-at-home theory and, 71–73, 75
extramarital sex and, 69–70
many-fathers theory and, 71, 73–75
Sexual signals. See Signals
Shore birds, sex-role-reversal polyandry and, 26–29, 57
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
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
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
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
male pseudohermaphrodites and, 47
Zahavi’s handicap principle of signals, 132–33, 144–45
Zebras: harems and, 5
paternal care and, 3