Monogamy may be an evolutionary tactic to ward of aggressive males and prevent infanticide.
Committed males take better care of their offspring. The monogamous pairing allows the father to help out Mom andd protect the family from violent unrelated males, a University College London press release reported.
"This is the first time that the theories for the evolution of monogamy have been systematically tested, conclusively showing that infanticide is the driver of monogamy. This brings to a close the long running debate about the origin of monogamy in primates," Dr. Kit Opie, lead author of the study, said.
Infants are most vulnerable when completely dependent on their mothers. Nursing females delay conception, which could lead an unrelated male to kill the infant in favor of conceiving his own.
If the father helps out with the young's upbringing they often become independent faster, allowing for more frequent pregnancies.
Females who have male support are also able to have more "costly" offspring with larger brains. Baby animals with larger brains develop slower than smaller-brained species. If a father is there to shoulder some of the burden, it's easier for offspring to survive through longer childhoods.
These findings could help explain how humans' brains developed to lean towards monogamy. Primates in general have large brains and long childhoods, but the mothers are able to reproduce relatively frequently.
A research team looked at data from 230 species of primate. They created a "family tree" of their relationships.
The research allowed the team to find where and when certain traits (such as monogamy) emerged.
"This then allowed the team to determine the timing of trait evolution and show that male infanticide is the cause of the switch from a multi-male mating system to monogamy in primates, while bi-parental care and solitary ranging by females are a result of monogamy, not the cause," the press release stated.
Primates aren't the only members of the animal kingdom that mate for life. Alpha male wolves often have an alpha female by their side. Mom and Dad beavers share the hard work of raising their kits. Male penguins present their lady with an "engagement ring" pebble, though they only stay together for one mating season.
Among other monogamous animals are: black vultures, eagles, swans, prairies voles, and French angelfish, Mother Nature Network reported.
