'X' became symbolic for a kiss because in the middle ages when alot of people were illiterate and they used to sign documents with an X and then kiss it for sincerity.
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Brain scans show that people who view photos of a beloved experience an activation of the caudate - the part of the brain involving cravings.
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One in five long-term love relationships began with one or both partners being involved with others.
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In medieval Italy, if a man was caught kissing a woman in public, he had to marry her whether he liked it or not.
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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.
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In 2011, archaeologists discovered the skeletal remains of a Roman couple who have been holding hands for 1,500 years.
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Every year around 1 billion Valentine cards are sent. After Christmas it's a single largest seasonal card-sending occasion.
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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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