Sudan, the world's last male northern white rhino, has died, putting his species on the brink of extinction

Unable to stand, and suffering from a string of infections in his advanced age, the world's last male northern white rhino was euthanized Monday by a veterinary team in Kenya that had fought for years to save him and his dwindling species. Only two now remain - his daughter, Najin, and granddaughter, Fatu - leaving in vitro fertilization from preserved sperm as the last tool against extinction.