Forgot where I read it, but apparently ancient cacs would sleep with their animals in their huts and viewed them like family. Probably why they're so comfortable with the face licking
And before then they lived in caves with wild animals to avoid the cold, and it is in these dark and freezing conditions they picked up a lot of the revolting and inexplicable behaviors and traits we see today.
Its how the Rhesus monkey gene ended up in European genes.
Its how the common cold was an avian illness that jumped to humans in Europe, from Europeans living with birds indoors.