Why have the English Overbite?

My theory is that so many people in the UK, at least England or Britain or whatever they call it, well, why so many people seem to have over bites or buck teeth (not making british teeth jokes I promise) is due to their accent or the fact they've been breeding on a small island for thousands of years with some influx of German and French etc.

The overbite is genetic or a product of their accent, or my completely silly confirmation bias.