single-species hypothesis

The "single-species hypothesis" in anthropology proposed that only one species of culture-bearing hominin could exist at any given time. This idea suggested that all hominin fossils should fit into a single evolutionary lineage. Proponents later adapted this to view Homo sapiens as an extremely variable species with deep roots, encompassing all subsequent hominins like H. erectus and H. neanderthalensis within it.1

This "multiregional" view suggested that distinct modern human populations evolved separately in different parts of the world, with interbreeding maintaining species unity. However, this concept is challenged by evolutionary principles, as significant changes typically occur in small, isolated populations, not large ones. The prevailing "out of Africa" model posits that H. sapiens evolved in Africa and then migrated, replacing earlier hominin populations with limited interbreeding. Genetic evidence strongly supports this African origin, indicating that modern humans share a common ancestor from a small African population.1