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Eggs: larger than sperm; menopause and depletion of

Electrical signals

Electric fishes, signals and

Elephants: eggs of; menopause and; pregnancy and

Enzymes, male/female organ development and

Epididymis

Estrogen, lactation and

Estrus, mammals confining sex to. See also Fertilization, mammals having sex for

Evolution: of concealed ovulation; human sexuality and. See also Natural selection

Evolutionary commitment; birds’ reproductive strategy and; mammalian reproductive strategy and

External fertilization; alternative opportunities foreclosed by child care and; in fish; humans and; obligate parental investment and; parental care and

Extramarital sex; biological significance of; confidence of parenthood and; hunting and; recreational sex and; as risky; sex appeal and; sex differences in attitudes toward

Extra-pair copulations, of Pied Flycatchers

Facial beauty, as human signal

Fallopian tubes

Fat, as signal in human females

Female menopause. See Menopause

Females (human): breasts and; buttocks and; extramarital sex and; facial beauty and; fat and; fertility decline in, see also Menopause; hormones and breast development and; lactation by; parental care and; plant foods gathered by; sexual maturity of; sexual ornamentation and. See also Concealed ovulation; Lactation; Menopause; Sexual receptivity (female)

Females (mammalian): duration of fertility of; lactation and; menopause and; parental care and; sex-role-reversal polyandry and; signals and

Fertilization, mammals having sex for. See also External fertilization; Internal fertilization

Fish: external fertilization and; male role and; mating systems of; parental care and; vivipary and

Fisher, Ronald, Sir

Fisher’s runaway selection model of signals

Flycatchers. See Pied Flycatchers

Ford, Henry

Foreclosed opportunity, parental care and

Frogs: mating systems of; parental care and

Fun, sex for. See Recreational sex

Genes; males passing to offspring. See also Chromosomes; Natural selection

Genetic testing, confidence of parenthood and

Gibbons: couples and; as monogamous; parental care and; paternal care and; sex confined to estrus and; sexual distinctiveness and

Glans penis

Glass frogs, parental care and

Goats (female), lactation in virgin: hormones and; “milking” and

Goats (male), lactation and: hormones and; spontaneous lactation and

Gorillas: harems and; head shape indicating sex and; humans compared to; infanticide and; ovulatory signals and; paternal care and; penis of; sex and parental care and; sexual distinctiveness and; sexuality of; sexual maturity indicated and

Grandmothers, extended role of

Great apes. See Apes

Great Tits, breast stripe as signal and

Growth hormone. See Somatotropin

Guinea pigs, lactation and; hormones and male lactation and

Hadza, foraging by women of different ages and

Hammer-headed fruit bats, lek mating system of

Hamsters, duration of fertility of

Handicap principle. See Zahavi’s handicap principle of signals

Harems: concealed ovulation and; humans and; mammals and; primates and

Hawkes, Kristen

Hazda Indians, hunting by men of

Head shape, gender indicated by

Herring Gulls, signals and

Hill, Kim

Hoofed mammals, lack of paternal care and

Hormones: lactation and; male lactation and; sex differences and

Howler monkeys, concealed ovulation and

Hrdy, Sarah

Human sexuality: apes compared to; apparent inefficiency of; continuous practice of sex and, see Sexual receptivity (female); coparenting and; evolutionary biology and; extramarital sex and; harems and; internal fertilization and; long-term sexual partnerships and; mammalian sexuality compared to; monogamy and; ovulatory signals and, see Concealed ovulation; polyandry and; polygyny and; premarital sex and; private sex and; promiscuity and; proximity to sexual partnerships of others and; sequential monogamy and. See also Concealed ovulation; Females (human); Males (human); Menopause; Parental care (human); Recreational sex; Sexual receptivity (female)

Human signals; age; facial beauty; handicap principle of; male voice; men