The dowdy peahen chooses the ornamental peacock as her mate. Male elephant seals use their bulk and weight to fight for a harem of females. A hornbill walls herself up for weeks and depends entirely on a devoted mate for food. Why such variety?

James Gould, a professor of biology at Princeton University, has an explanation for all mating habits - including our own. Every animal is in search of a bargain from the opposite sex. Every animal is doing its best to make sex pay.

(R) (Ceefax Subtitles)

"...a refreshingly frivolous 'Horizon'." (Independent)
"...delicious fantasy with a serious purpose..." (Daily Mail)