In 1971, taxidermist Reinhold Rau realized that the quagga's genes had not been forever lost. Zebras had occasionally interbred with quagga over the millenniums, and some of the descendants of these pairings still roamed South Africa. Rau surmised that he could retrace evolution's trail by mating the most quagga-looking zebras he could find and then mating certain of the offspring. In each generation, quagga genes will be further concentrated—so that eventually, Rau believes, two zebras will produce a real quagga.