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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Photos: Which animals are monogamous?
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.
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Photos: Which animals are monogamous?
Primates such as chimpanzees and bonobo monkeys, pictured, do not conform to a mating system and regularly engage in frequent sex with multiple partners.
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Photos: Which animals are monogamous?
Emperor penguins usually mate for one year before moving on to a new partner.
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Photos: Which animals are monogamous?
Male elephant seals, or "beach masters," protect harems of more than 100 females from other males thinking of moving into their territories.
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Photos: Which animals are monogamous?
Swans -- symbols of love and fidelity -- are not monogamous.
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