A biologist has determined that a harem lifestyle was bad for a female rate of reproduction.   

Mormon leader Brigham Young had 55 wives and conceived 56 children before he died in 1877. His followers had similar polygamous marriages.   But scientists have now uncovered an odd fact about 19th-century Mormons: the more women in a household, the lower the average birthrate. In other words, the more sister-wives a Mormon woman had, the fewer children she was likely to produce.

The result is intriguing, because this is the first time scientists have observed humans being affected by what is known as the Bateman gradient, a phenomenon that gets its name from the geneticist who first observed it in fruit flies. The more sexual partners the male fruit fly had, the lower was the fecundity of each of those partners, the 20th-century geneticist Angus Bateman noted.

Science editor Robin McKie of Guardian News has the story.