Genetic analysis of 400+ modern humans finds zero evidence of interbreeding with regional ancient humans. Denisovan ancestry confirmed at high levels in Island Southeast Asia populations. Modern humans interbred with Denisovans 50,000-60,000 years ago during migration to Australia. Homo erectus, floresiensis, and luzonensis lineages too ancient to be Denisovans. Denisovans known mainly from DNA, with sparse fossils in Siberia and Tibet. No Denisovan fossils yet in Island Southeast Asia despite DNA evidence. Study urges re-examination of local fossil record for Denisovans. Pre-modern humans may explain megafauna survival in region versus extinctions in Australia.