Early Human Ancestors May Be 1 Million Years Older Than Scientists Previously Thought
Mrs. Ples is a very famous cavewoman today. Deep in the labyrinth of rocks, her remains lie along with some other ancient fossils in South Africa’s Cradle of Humankind. For years, scientists thought the species Mrs. Ples belonged to, called the Australopithecus africanus, were less than 2.6 million years old. But a recent discovery of a wealth of fossils put this timeline on the fritz: fossils belonging to Mrs. Ples and others are one million years older than scientists previously thought.
This new timeline does two things: it complicates our current understanding of where humans came from and thus, reshapes what we understand about human evolution.
Our relationship with Mrs. Ples and the rest of the Australopithecus is such: Australopithecus are a group of extinct primates related to, if not actually ancestors of, modern humans. They are a genus of early hominins believed to have existed in Africa.
The findings were published in the Proceedings of the National Academy of Sciences on Monday. What led to this discovery was an innovative dating technique using radioactive means researchers tried out. Within the Cradle of Humankind is a complex system made of limestones called the Sterkfontein Caves; it is where the first adult Australopithecus, an ancient hominin, was discovered in 1936. Since then, scientists have discovered several of them — famous among them is also “Little Foot,” the most complete Australopithecus skeleton, who is believed to have lived some 3.67 million years ago.
“What our data does is resolve these controversies. It shows that these fossils are old — much older than we originally thought” said lead study author Darryl Granger, professor of Earth, atmospheric and planetary sciences at Purdue University.
Think of it this way: if mapping human evolution is like a big, complex jigsaw puzzle, dating the fossils to their accurate timeline is like putting a piece back to its designated place. It not only gives scientists critical background context, but allows them to understand how and where humans evolved. They also expand the realm of possibility on how ancestors could have evolved into early humans.
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Here’s what we know about the Australopithecus: they walked on two feet, and were much shorter than modern-day humans. Males were about 4ft 6in height on average, and females averaged a 3ft 9in, according to Smithsonian Mag.
Scientists thought them too young to have evolved into our ancestors (homo genus), who were present some 2.2 million years ago. The new dating pushes back that timeline to argue they had an additional one million years to “make that evolutionary leap — making it a possibility that Mrs. Ples, and the species she was part of, were ancestors of early humans,” as BBC explained.
If true, then the species would have existed at the same time as another ape species — Africa’s Australopithecus afarensis — that is believed to have given rise to the earliest humans. Among them is Lucy, whose 3.2-million-year-old remains spawned this theory. Lucy is also believed to be one of the oldest known human ancestors.
But also, there’s an element of chaos at play, as scientists think it’s possible the two species (Australopithecus africanus and Australopithecus afarensis) could have just interbred while existing at the same time. Our family tree is then “more like a bush,” said French scientist Laurent Bruxelles who was part of the study, referring to how this complicates our evolutionary trajectory. It’s beginning to look more like a zig-zag than a straight line of evolution.
Gauging the age of the Australopiths tells a story of how South Africa played a role in the diversification of early human ancestors. “Using this method, we can more accurately place ancient humans and their relatives in the correct time periods, in Africa, and elsewhere across the world,” said Granger. This will unearth stories of evolution, relatives, and how humans fit into the ecosystem — then and now.