The word sex means a lot of things. In popular culture, sex refers to gender, to sexual intercourse, and to physical intimacy with or without sexual intercourse. The word sex is used in any and all connections to the imagery, sounds, rhythms, emotions, and desires that promote the frequencies of sexual energy.
In science, sex is the combination of genetic material from two organisms. This usually results in reproduction, the creation of new organisms. Sex may occur without reproduction being directly attached, as in some varieties of bacteria that exchange genetic material without reproducing. Reproduction can also take place asexually, where the parent organism reproduces its genes and buds off a new individual that is a clone of the parent.
In evolution, both sexual and asexual reproduction have their advantages, and there are even species which flip back and forth depending on environmental conditions.
In evolutionary biology, sex is a powerful mechanism by which a species evolves. Sexual selection for desirable (read: good for survival) traits takes place at the level of the individual and also at the level of the species. Since the environment is always changing, even if the pace is sometimes glacial, species have to keep adapting in order to stay current. This has become known as the “Red Queen” hypothesis after the Red Queen in Alice in Wonderland who tells Alice, “it takes all the running you can do to keep in the same place.”
Sex for scientists leads equally to the brilliant feathers of a peacock and the preference of human men for a female waist-to-hips ratio of seven-tenths. It encompasses the drift of pollen in the air, the fast swim of a male fish to deposit his sperm over a female’s eggs in the water, and the harem-keeping of a silverback gorilla.
There are an astonishing variety of sexual strategies in different species. Perhaps the strangest for humans to imagine is the strategy of one type of mite. The females produce 9 female embryos for every male embryo. While still in the womb, the male impregnates all the females, who, having no more use for him, eat him. The females then eat their way out of the mother’s body, already pregnant and beginning the cycle again.
Sex is strange and weird and wonderful for scientists, who at every level see both the simplicity of gene combination, and the complexity of strategies for sexual reproduction.
Come to think of it, non-scientists also see it as both simple and bewildering. Nature doesn’t have it any other way.
Dorion Sagan, Sex
Joann Ellison Rodgers, Sex: A Natural History
Arndt von Hippel, Human Evolutionary Biology