>From Stephen Pinker *How the Mind Works*:
"Bonobo (pygmy chimp) females are almost indiscriminately promiscuous, and the males fight less and are about the same size as females. They compete in a different way: inside the females' bodies.
Sperm can survive in the vagina for several days, so a promiscuous female can have several males' sperm competing in her for a chance at fertilizing the egg. The more sperm a male produces, the greater the chance that one of his will get there first. That explains why chimpanzees have enormous testicles for there body size. Bigger testes make more sperm which have a better chance inside promiscuous females. A gorilla is four times the weight of a chimpanzee, but his testicles are four times smaller. The females in his harem have no chance to copulate with another male, so his sperm do not have to compete. Gibbons who are monogamous have small testicles too.
In almost all primates (indeed, in almost all mammals) the males are deadbeat dads contributing nothing but their DNA..." p466
BTW, some species are solitary like female Gibbons, Oragutans and Gorillas. The philosopher Philip Kitcher describes these species as 'asocial' they always opt out of prisoner dilemmas's and are susceptible to invasion by egoistic species making the asocial strategy a non evolutionary stable strategy. Maybe this is why most of these species are near extinct.
While I'm at it:
TABLOID HEADLINES:
CHICAGO CHAUFFEUR SMOTHER'S BOSSES DAUGHTER, THEN CUTS HER UP AND STUFFS HER IN FURNACE
DOCTOR'S WIFE AND LOCAL MINISTER EXPOSED FOR CONCEIVING ILLEGITIMATE DAUGHTER
TEENAGERS COMMIT DOUBLE SUICIDE FAMILIES VOW TO END VENDETTA
STUDENT CONFESSES TO AXE MURDER OF LOCAL PAWNBROKER AND ASSISTANT
GARAGE OWNER STALKS AFFLUENT BUSINESSMAN, THEN SHOTGUNS HIM IN SWIMMING POOL
MADWOMAN LONG IMPRISONED IN ATTIC SETS HOUSE ON FIRE, THEN LEAPS TO DEATH
FORMER SCHOOLTEACHER, FOUND TO HAVE BEEN PROSTITUTE, COMMITTED TO INSANE ASYLUM
PRINCE ACQUITTED OF KILLING MOTHER IN REVENGE FOR MURDER OF HIS FATHER
All sound familiar?:
[Native Son, by Richard Wright; The Scarlet Letter by Nathaniel Hawthorne; Romeo and Juliet by William Shakespeare; Crime and Punishment by Fyodor Dostoevski; The Great Gatsby by F.Scott Fitzgerald; Jane Eyre by Charlotte Bronte; A Streetcar Named Desire by T.Williams; Eumenides by Aeschylus.]
Lederer and Gilleland *Literary Trivia* quoted in Pinker p 542.
Sam Pawlett