Afarensis dating

Every so often, a curious thing happens to the Earth’s magnetic field.

Last month, many around the world read about the unveiling of the remarkably intact remains of two Australopithecus sediba individuals from the Malapa cave site in South Africa.

What these remains mean for the way we draw our family tree – are they or aren’t they our direct ancestors, for instance – is still being debated.

One thing that is certain, however, is that the remains fit into a previously rather barren period in the fossil record of early hominids.

Before their discovery by paleoanthropologist Lee Berger and his son in 2008, there were fossils of Homo erectus, the earliest known representative of our own genus Homo, which were dated to around 1.9 million years old.

Then there was Lucy, a fossil remain from the pre-Homo hominid Austraopithecus afarensis.

Lucy was found in Ethiopia and dated to 3.2 million years ago.

At the 2 million year mark, the crucial transition point when Australopithecus became Homo, few fossil remains existed. sediba individuals found at the Malapa cave site some 60 km northwest of Johannesburg met their demise at almost precisely this time.

In fact, the age estimate for the skeletons is 1.977 years old, give or take 2000 years – a remarkably precise approximation given their antiquity.

Dr Robyn Pickering, a geochemist working at the School of Earth Sciences at the University of Melbourne, is the lead author on a paper in the journal Science that describes how Australopithecus sediba was dated so accurately.

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