Why does your female puppy beagle hump your female adult golden retriever?

Humping is a one way that canines try to display dominance. It is often part of the puppy learning their place in the pack. They can start trying to display they are "top dog" at a very young age. Males and females do this. If the adult has been in the family and comfortable in their position, they will likely put the pup in their place sooner or later.