Scientists have revealed a surprisingly complex origin of our species, rejecting the long-held argument that modern humans arose from one place in Africa during one period in time.

By analyzing the genomes of 290 living people, researchers concluded that modern humans descended from at least two populations that coexisted in Africa for a million years before merging in several independent events across the continent. The findings were published on Wednesday in Nature.

“There is no single birthplace,” said Eleanor Scerri, an evolutionary archaeologist at the Max Planck Institute for Geoarchaeology in Jena, Germany, who was not involved in the new study. “It really puts a nail in the coffin of that idea.”

Paleoanthropologists and geneticists have found evidence pointing to Africa as the origin of our species. The oldest fossils that may belong to modern humans, dating back as far as 300,000 years, have been unearthed there. So were the oldest stone tools used by our ancestors.

Human DNA also points to Africa. Living Africans have a vast amount of genetic diversity compared with other people. That’s because humans lived and evolved in Africa for thousands of generations before small groups — with comparatively small gene pools — began expanding to other continents.

Within the vast expanse of Africa, researchers have proposed various places as the birthplace of our species. Early humanlike fossils in Ethiopia led some researchers to look to East Africa. But some living groups of people in South Africa appeared to be very distantly related to other Africans, suggesting that humans might have a deep history there instead.

Brenna Henn, a geneticist at the University of California, Davis, and her colleagues developed software to run large-scale simulations of human history. The researchers created many scenarios of different populations existing in Africa over different periods of time and then observed which ones could produce the diversity of DNA found in people alive today.

“We could ask what types of models are really plausible for the African continent,” Dr. Henn said.