How many races of people have existed on the planet earth to date and how long have the races that are hear today been here?

As far as the basic category Homo Sapiens - what you and I call "human beings", the races extant today are the races that originally evolved on earth save one: Homo Sapiens Neanderthalis, which died out about 25,000 years ago on the Gibraltar coast of Spain. Neanderthals were true humans, but for reasons not fully understood, that branch of mankind died out as stated above. How long have we been here? Mostly a matter of definition. If you stick with all inclusive members of Homo Sapiens, a few hundred thousand years. If you take one step backwards to all species of the genus Homo, about four million years.