In 1889, a French doctor named Francois-Gilbert Viault climbed down from a mountain in the Andes, drew blood from his arm and inspected it under a microscope. In the early 1900s, scientists theorized that a hormone was the cause. Seven decades later, researchers found actual erythropoietin after filtering 670 gallons of urine. And about 50 years later, biologists in Israel announced they had found a rare kidney