Hominid fossils from Ngandong and Sambungmacan, Central Java, are considered the most morphologically advanced representatives of Homo erectus. Electron spin resonance (ESR) and mass spectrometric U-series dating of fossil bovid teeth collected from the hominid-bearing levels at these sites gave mean ages of 27 +/- 2 to 53.3 +/- 4 thousand years ago; the range in ages reflects uncertainties in uranium migration histories. These ages are 20,000 to 400,000 years younger than previous age estimates for these hominids and indicate that H. erectus may have survived on Java at least 250,000 years longer than on the Asian mainland, and perhaps 1 million years longer than in Africa. The new ages raise the possibility that H. erectus overlapped in time with anatomically modern humans (H. sapiens) in Southeast Asia.