The earliest species of human is thought to have evolved from East Africa based on fossil findings, including that of the famous Lucy, an Australopithecus afarensis who lived in what is now Ethiopia some 3.2 million years ago. But that theory might now be shifting thanks to new findings across the continent. As the AFP reports, a new analysis of fossil remains of the Australopithecus africanus species discovered in South Africa in the first half of the 20th century and initially dated to between 2.1 and 2.6 million years old shows they are actually more than a million years older—perhaps old enough to represent an ancestor of the Homo genus.
The South African Australopithecus members were in fact "contemporaries" of Lucy and her East African mates, says Dominic Stratford, director of research at the Sterkfontein caves at the Cradle of Humankind world heritage site northwest of Johannesburg and author of a study published Monday in the Proceedings of the National Academy of Sciences. After cosmogenic nuclide dating in 2015 determined a near-complete skeleton of an Australopithecus at the cave, known as "Little Foot," was actually between 3.4 and 3.7 million years old, researchers began testing rocks around other fossils, including "Mrs. Ples," the most complete skull of an Australopithecus africanus ever found, per Insider.
The fossils themselves are too fragile to test. But in looking at levels of rare isotopes in nearby rocks hit by cosmic rays, researchers can determine when they were buried. The process indicated Mrs. Ples and other nearby fossils are also between 3.4 and 3.7 million years old. Researchers say the earlier estimate was incorrect as it measured calcite flowstone mineral deposits that are younger than the rest of the cave section. "Over a timeframe of millions of years, at only [2,500 miles] away, these species had plenty of time to travel, to breed with each other," before humans appeared, geologist and study author Laurent Bruxelles tells the Guardian. (Read more evolution stories.)