Why did we become monogamous?

By Meera Senthilingam, for CNN

Updated 1905 GMT (0305 HKT) May 18, 2016

Humans are now mostly monogamous, but this has been the norm for just the past 1,000 years.<br /><br />Scientists at University College London believe monogamy emerged so males could protect their infants from other males in ancestral groups who may kill them in order to mate with their mothers.
Photos: Which animals are monogamous?
Humans are now mostly monogamous, but this has been the norm for just the past 1,000 years.

Scientists at University College London believe monogamy emerged so males could protect their infants from other males in ancestral groups who may kill them in order to mate with their mothers.
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Scientists in Canada recently suggested that a rise in sexually transmitted infections, as social groups became larger among early humans, would have put pressure on staying monogamous in terms of mating behavior.