It will come as no surprise to those interested in the animal world as a whole that human beings did not invent the idea of group sexual activity.

Arthropods, for example, frequently engage in such practices, as do various more highly developed species. Cetaceans- porpoises, for example - are particularly keen on various group sex activities, and so are their larger brothers and sisters, the whales. Of Grey Whales H. Wendt noted in "The Sex Life of Animals": -

"Another interesting habit is that mating is done in three's, one female and two males. The role of the second male is not well understood but it has something to do with mutual assistance."

When we think of the size of these creatures perhaps we begin to appreciate why some "mutual assistance" in mating is required.