Originally Posted by Grelev
It probably didn't happen overnight. I'd figure that they didn't give their fleets up per se, but combined them under starfleet. i would imagine the early Federation Starfleet having a lot of ships from not only Earth, but from Vulcan, Tellar and Andoria. As they came together to design and build "Starfleet" ships, the older models were phased out for a more uniform style fleet.
Well put. Eventually the techincal expertise of humans, Vulcans, Andorians, and Tellarites was combined into new classes of starship.
There is a popular theory that the reason the Federation and Starfleet were headquartered on Earth is because it was the one race that all others trusted prior to the founding of the UFP. The government of United Earth was allied with the Vulcans, on friendly, cooperative terms with the Andorians, and appeared to have no conflict with the Tellarites. As a result, those races had every reason to make Earth the capital of their new interstellar government.