Kissing originated as an attempt to remove lice.
Kissing was originally an attempt to remove lice and ticks from fur
A scientific paper has argued that the practice of locking lips has disgusting origins as it was used by our ancestors to remove both ticks and lice from fur.
Adriana Lameira, an evolutionary psychologist at the University of Warwick, became interested in the origins of smooching last year after historians revealed that the practice dates back to 2500 BC.
Lameira believes that gorillas used their mouths to remove ticks and debris before the grooming ritual was minimised until just the last kiss-like stage remained.
He said: "This final step, when the (ape) groomer closes the grooming bout by 'kissing' the groomed, exhibits parallels in form, context and function to human kissing to an extent that no other proposed behaviour thus far has.
"What was once a time and labour-intensive ritual to cement and strengthen close social ties became gradually compressed until a groomer's final kiss turned into a crystallised symbol of trust and affiliation."