With under 40 pupfish left in the wild, these are possibly the rarest fish on the planet. The Devils Hole pupfish have existed in isolation for thousands of years in an extreme environment where few species could survive. How did they end up in such an inhospitable place? And what makes their survival so important? Untold Earth explores the seeming impossibilities behind our planet’s strangest, most unique natural wonders. From fragile, untouched ecosystems to familiar but unexplained occurrence