Why did we become monogamous?

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.
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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