There is only one Pinta Island tortoise (Geochelone elephantopus abingdoni) known left in the wild. When George dies the Pinta tortoises will be extinct.
Once there were millions of giant tortoises. In the age of the dinosaurs they covered most of the Americas, Europe and Asia. Like other dinosaurs they began to die out when mammals evolved and they were neither clever enough nor fast enough to compete for food.
Although it is always terrible when a species become extinct, this can sometimes be unavoidable once it gets to this level. Also, the other Giant Galapagos tortoise may be able to take its place (if ecologists think it will be environmentally beneficial). Lonesome George is one of several subspecies of Giant Galapagos tortoise.
Actually Pinta Island Tortoises were considered extinct until a ranger found one, the one we all know Lonesome George, in 1971. Since then, many researchers and activists have offered monetary rewards and compensation to anyone who is able to recover another, preferably a female.
George is penned with two females of a different subspecies, Geochelone nigra becki from the Wolf Volcano region of Isabela island, in the hope that his genotype would be retained in the resulting progeny. This subspecies was thought to be genetically closest to George's; however any offspring successfully hatched from George and his consorts would be intergrades, not purebreds of the Pinta subspecies.
You can read more facts and information of the Pinta Island Tortoise at the wiki page.