Scientists have found evidence suggesting that kissing dates back up to 21 million years and that our ape ancestors and Neanderthals likely locked lips, research published Wednesday said.

Kissing has long presented an evolutionary puzzle to scientists as it appears to carry high risks such as disease transmission while having no obvious reproductive or survival advantages.

But the new study found that the practice has evolved over millions of years, and that our extinct human relatives, the Neanderthals, could have shared a peck to stay warm in the ice age.

The research led by scientists at the University of Oxford was published in the journal "Evolution and Human Behaviour".

"This is the first time anyone has taken a broad evolutionary lens to examine kissing," said co-author Matilda

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