Love doesn't just exist in humans. Many species across the animal kingdom have life-long monogamous mates.
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Key Facts In This Video
People who are in love have heartbeats that sync up when they look at each other. 00:57
Sex is a key indicator of the bond between a couple. 06:08
Oxytocin is known as the "attachment hormone." 08:33
Written by Curiosity Staff February 13, 2015
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