The Sexes

abortion adult animals ants baby become beetle behavior birds birth control birth rate body breeding cells cent chemical chromosomes cloaca colony contraceptive copulation creatures culture developed dogs early effect eggs evolution example fact family planning feed female's fertilized eggs fish fleas flies fungus genes girls glands growth habits hatched hermaphroditic hormones human Hutterites incest increase Indian insects instinct intercourse intrauterine device killed kind larvae live lizards male and female male's mammals marriage married mating mature menarche mice million modern mother nest normal offspring organs orgasm ovaries ovulation pair parasites parthenogenesis pecking order penis perhaps pituitary plants population control population density predators pregnant primitive probably queen rabbit rats reason reproduction result rhythm method semen sexual snail snakes social society species sperm spiders technique temperature termite territorial tion Trobriand Islanders usually uterus vagina vertebrates wasps wild woman women worms young