In the past 100000 years four kinds of humans coexisted. They are early modern humans, Neanderthals, Homo floresiensis , and Denisovans. Early modern humans are ancestors of extant humans and have fundmentally similar morphology to that of ours. Neanderthals are slightly shorter than modern humans. They have robust extremities and larger brain volume, Neanderthals inhabited widely in Europe and also distributed in West and Central Asia. They disappeared around 30000 year ago. Evidence of DNA analysis and morphology verified the gene flow between Neanderthals and early modern humans. The genes with Neanderthal ancestry in the genome of extant humans have definite influences on the physiology, morphology and risk for certain diseases in extant humans. Fossils of Homo floresiensis were unearthed only in Flores Island, Indonesia. This kind of humans is very short, with cranial capacity as small as one third of extant humans. They lived 100000–60000 years ago. The origin and their relation with other kinds of humans are mysteries. Fossils of Denisovans were unearthed only at Denisova Cave of Altai region, south Siberia of Russia and only a finger bone and two teeth were found. Denisovans are identified by DNA analysis and lived around 40000 years ago. In the genome of Melanesians 4.8%± 0.5% are derived from Denisovans. It is suggested that the gene flow with Denisovans was helpful for the adaptation of Tibetans to the high plateau environment. Paleo-DNA study also suggests that perhaps another kind of humans coexisted with our ancestor during this period.