Kissing, animals do it, humans do it. When did it start

[Catherine]

Scientists have been studying kissing in animals and people now and in the past. It goes back a long way, about 21 million years back.
The list of animals that kiss is long. All the primates do it. Humans and Neanderthals didn't just kiss, they probably kissed each other.
The one question they haven't answered is why.

https://www.bbc.com/news/articles/cr43gq61g2qo

This is something I never thought about. We all kiss things and people and there creatures. I don't know why I do it.
My little guinea pig looks like he needs a kiss. Now I an going to be thinking about why and looking around to see if any other creatures in my life kiss each other.