In 2011, archaeologists discovered the skeletal remains of a Roman couple who have been holding hands for 1,500 years.
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When a male gentoo penguin "falls in love" with a female penguin, he searches the entire beach to find the perfect pebble to present to her.
25
Couples' personalities converge over time to make partners more and more similar.
235
Every year around 1 billion Valentine cards are sent. After Christmas it's a single largest seasonal card-sending occasion.
14
The typical person spends about 600 hours having sex between the ages of 20 and 70.
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8 out of 10 people think that the first kiss indicates how the rest of the relationship will be.
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A Korean man called Lee Jin-gyu fell in love with his large, huggable pillow and married it.
29
Brain scans show that people who view photos of a beloved experience an activation of the caudate - the part of the brain involving cravings.
103