By 1880, when most "tarpans" may have become hybrids, wild horses became very rare. Peter Simon Pallas witnessed possible wild tarpans in the same year in southern Russia. The color of pure tarpans was described as constantly brown, cream-colored or mouse-colored. Some of these horses are now commercially promoted as "tarpans". In addition, tarpans that lived into modern times may have been hybridized with domestic horses. Tarpans survived the longest in the southern parts of the Russian steppe. "The Natural History of Horses" by 19th-century author Charles Hamilton Smith also described tarpans.