The Coexistence and Disappearance of Multiple Human Species

Key Insight

For most of the last 2 million years, Earth was home to several distinct human species, not a single linear progression. Humans evolved in East Africa from the ape genus Australopithecus about 2.5 million years ago. Around 2 million years ago, some groups migrated out of Africa, settling vast areas of North Africa, Europe, and Asia, leading to the evolution of diverse human species adapted to varied climates.

Notable species included Homo neanderthalensis, 'Neanderthals,' in Europe and western Asia, who were bulkier, more muscular, and possessed larger brains than Sapiens, well-adapted to Ice Age conditions and known for caring for their sick. Homo erectus, 'Upright Man,' inhabited eastern Asia for almost 2 million years, making it the most durable human species. Other forms, such as Homo soloensis in Java, the dwarf Homo floresiensis on Flores Island, and Homo denisova in Siberia, further demonstrate this ancient human diversity.

The co-existence of multiple human species ended around 10000 years ago. The expansion of Homo sapiens from East Africa about 70000 years ago coincided with the disappearance of these other species. Theories propose either interbreeding, where Sapiens merged with other populations like Neanderthals (evidenced by 1–4% Neanderthal DNA in modern Eurasians and up to 6% Denisovan DNA in Melanesians/Aboriginal Australians), or replacement, where Sapiens drove other species to extinction through competition for resources, violence, or genocide, given Sapiens' limited tolerance for difference. The last Homo soloensis vanished 50000 years ago, Neanderthals 30000 years ago, and Homo floresiensis 12000 years ago, leaving Homo sapiens as the sole surviving human species.