Although there is an average age for when puberty begins, it doesn’t always start at the same time for every gURL or guy. There are a lot of different factors that go into when puberty begins that you probably never really thought about.
The age at which puberty begins is affected by genetic factors and also environmental factors. It can also vary because of social circumstances, like in the case of the Vandenbergh effect, which is when a gURL hangs out with a lot of guys and then enters puberty earlier.
Puberty can also be affected by your race. The earliest onset age of puberty is for African-American gURLs, and the latest onset is for gURLs in some parts of Asia.