In the 1970s, amateur collectors discovered a batch of human skulls and teeth fossils at the Cailiao River Valley in the Zuozhen District, Tainan City. After fluorine dating was conducted, the fossils were confirmed to be between 20,000 and 30,000 years old.They belonged to homo sapiens from the late Paleolithic Age, and are the earliest human fossils yet found in Taiwan. Since the remains were excavated at the Cailiao River in the Zuozhen District, Tainan City, they are referred to as the “Zuozhen Men”.