South Africa
The skull of an ancient cave dweller unearthed in South Africa is a million years older than had been thought, reshaping the understanding of human evolution.
Scientists have long held that fossils of the Australopithecus africanus, discovered in the Sterkfontein cave network near Johannesburg, were less than
2.6 million years old. The trove included the species’ most complete skull, dubbed Mrs Ples, found in 1947.
Advanced testing methods now suggest Mrs Ples lived between 3.4 and 3.7 million years ago, making it possible that her species were early ancestors of humans. Although they walked upright and measured between 3.9ft and 4.6ft, the Australopithecus africanus were previously considered too young to have given rise to the homo genus, which includes human ancestors who lived 2.2 million years ago.
The findings, published this week in the Proceedings of the National Academy of Sciences, give the species about 1 million additional years to have evolved into the earliest humans. It suggests the Australopithecus africanus existed at about the same time as ‘‘Lucy’’, a 3.2-million-year-old cave woman found in northern Ethiopia in 1974 who belonged to the Australopithecus afarensis, long understood to be the species that most likely evolved into the earliest humans.
Scientists now say the two could have lived side by side and mated, meaning our family tree is ‘‘more like a bush’’, said Laurent Bruxelles, a French scientist who was part of the study. ‘‘Over a time frame of millions of years, at only 4000km, these species had plenty of time to travel, to breed with each other,’’ he said. ‘‘So we can largely imagine a common evolution across Africa.’’
The remnants are too old and brittle for scientists to test, forcing them instead to analyse sediment around them.
Researchers say scientists previously underestimated Mrs Ples’ age because they tested mineral deposits that were more recent than the rest of the sediment around her. This time they used a technique that measures levels of isotopes produced when rocks were exposed to high-speed particles.
Scientists had grown sceptical about the skull’s age because there was no sign of homo genus at the depth of the cave where it was found.