Bones of contention divide fossil fundis

It was a split second millions of years ago: Little Foot, possibly fleeing predators, fell into a concealed shaft in the Sterkfontein caves at the Cradle of Humankind, dying in a 20m fall.

The now-famous hominid's bones became a silent freeze-frame of our ancestry, preserved by layer upon layer of natural material that encased them.

As much as the cave system has been a treasure trove of evidence about our distant past, it has also pitted some of the world's sharpest scientific minds against one another.

And this week Little Foot's age - important in understanding the timeline of evolution - sparked fresh disagreement, the rival theories separated by an 800,000-year chasm.

Professors Jan Kramers of the University of Johannesburg and Paul Dirks of James Cook University in Australia claimed in a paper published in the South African Journal of Science that Little Foot was younger than 2.8million years and the hominid had first been in an upper chamber - now eroded away - before plunging to its death.

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This flew in the face of a 2015 report that put Little Foot at 3.67million years old - a view endorsed by the doyen of Little Foot experts, Professor Ronald Clarke of the University of the Witwatersrand.

Dirks said that because the fossil was embedded in breccia (sandy sediment), previous research "determined how long the quartz in that breccia had been underground and assumed that the age of the fossils must be the same as the age of the quartz [around 3.67million years]".

He and Kramers, however, looked at individual quartz fragments, "to work out when the grains came together", and concluded that the maximum time that had passed was 2.8million years.

The new research, said Dirks, suggested that "a cave chamber with sediment existed 2.8million years ago above the cave chamber in which Little Foot was found and that there was an opening between the two".

He said the apparent age contradiction could be explained if older sediment had eroded from the upper cave into the lower chamber and become mixed with the younger material.

Clarke dismissed the findings, even criticising the South African Journal of Science.

He told the Sunday Times this week: "It is unfortunate that a respected scientific journal publishes a paper based on fantasy rather than facts.

"The Kramers and Dirks paper is based on their fallacious suggestion of an imaginary upper chamber which they proposed has since been eroded away, and from which ... material found its way into the vicinity of the Little Foot skeleton.

"There is no geological indication for such an upper chamber existing at Sterkfontein."

He said he and other researchers were "very familiar with cases of collapse and mixture of later and earlier material within other parts of the Sterkfontein caves", but there was "absolutely no indication of such a collapse here".

Clarke said every indication uncovered by his research suggested Little Foot was more than 3.5million years old.

The new attempt to show otherwise was based on an "unsupported, imaginary scenario, which is in contradiction to the hard facts".

Clarke's connection to Little Foot began in 1994 when he discovered four bones from a left foot lying in a box of animal bones from the Sterkfontein cave system.

Three years later, in another box, he found more bones from the same foot, and set out to find the skeleton to which they belonged.

He and his assistants located a single bone sticking out of the rock, and it took a further 13 years to extract the Little Foot skeleton from its rocky matrix.

Clarke has been involved in research into Little Foot ever since. He is not the only one whose ire has been raised by the Kramers/Dirks paper.

French geomorphologist Laurent Bruxelles, another Sterkfontein expert, said he welcomed scientific "confrontations" but was outraged that previous research had been ignored in the new paper.

"This team didn't work on the cave and specifically on the cave deposits in which Little Foot is embedded. They are not even specialists in cave formations," he said.

"I cannot explain why the authors never contacted me to discuss this, share the results, and go together to the site to exchange our points of view."

Farbert@sundaytimes.co.za