The technique appears to show that fossils found in a South African cave are from a pre-human species which lived around 3.7 million years ago. At that time, a famous human ancestor known as Lucy lived in what is now Ethiopia, thousands of miles north, writes Alan Boyle for NBC News.

Scientists Say Two Pre-Human Species Co-Existed

Pre-human species: Little Foot and Lucy

The South African skeleton has been named Little Foot, and comes from a species known as Australopithecus, in the same group as Lucy. The age of Little Foot has been debated for over 10 years. This week, the latest findings were published in the journal Nature, and look set to provoke a new round of debate.

“Whether critics of the previous dating of Little Foot will be satisfied with this new work remains to be seen, but the skeleton once again highlights the diversity of pre-human forms in both East and South Africa,” said Chris Stringer, a paleoanthropologist at London’s Natural History Museum who was not part of the research team.

Lead researcher Darryl Granger, a geologist at Purdue University, said the new findings could answer a lot of questions about Little Foot, which is classified as Australopithecus prometheus. Paleoanthropologists noticed similarities with Lucy, an Australopithecus afarensis, but debate has raged as to whether the two species were contemporaries, or if Little Foot was a real human ancestor.

Pre-human species: Equipment upgrade leads to new results

Back in 2006, a different research team claimed that Little Foot was only 2.2 million years old, far lower than Granger’s first estimate of 4 million years. He accepted their conclusion based on good data, but the issue has bugged him ever since.

An upgrade to Purdue’s accelerator mass spectrometer allowed Granger and his team to check the radioisotope dates for Little Foot once again. This time the results aged the fossil at 3.67 million years.

It remains to be seen whether these results will be accepted, but if they are it will better fit Little Fit into the evolution of humanity. And it will provide further evidence that similar species co-existed in disparate regions.

Previous research has shown that early humans from the Homo genies were more diverse than previously thought, and now Granger claims Australopithecus was as well.