Little Foot's history revealed for the first time
- Wits University
Professor Ron Clarke's 14-year-long excavation of the Little Foot skeleton reveals her history through the ages.
The 14-year-long excavation and six-year cleaning and reconstruction process of the Australopithecus skeleton, known as Little Foot, from the Sterkfontein Caves in South Africa has revealed much about the individual, what happened to her after death, as well as how the skeleton was preserved.
The history of work on the 3.67 million-year-old fossil has been described for the first time by Professor Ron Clarke in the Journal of Human Evolution today.
In 1994 and 1997, Clarke identified 12 foot and lower leg bones of one Australopithecus individual misidentified as animal fossils in boxes stored at Sterkfontein and at the University of Witwatersrand. Clarke and his assistants, Stephen Motsumi and Nkwane Molefe, then looked for and located the very spot where the bones had been blasted out by lime miners decades earlier in a deep, dark part of the Sterkfontein Caves in the Cradle of Humankind, which is about 40km northwest of Johannesburg.
The team found contacts with two broken-through shin bones in a concrete-like cave infill and started the excavation process, first with hammer and chisel to remove the overburden, before turning to the painstaking process of locating and exposing the bones with an airscribe (a thick vibrating needle). What they’ve excavated turned out to be a virtually complete Australopithecus skeleton.
The excavation process, which was the first time ever that a nearly complete Australopithecus fossil has been excavated in place in a South African cave, has revealed that after falling into a deep cave, the female Australopithecus was mummified during dry conditions.
This was followed by slight displacement of some skeletal parts through slippage on the rock-strewn talus slope in the cave, crushing and breaking of some bones through rockfall and pressure, calcification after a change to wet conditions, and then slight downward collapse of part of the cave infill.
This partial collapse left voids that were later filled with stalagmitic flowstone that encased breaks through the femurs.
Early attempts at dating the skeleton had relied on the stalagmitic flowstone that encased the fossil. However, this excavation shows the flowstones were later infills in voids created by the collapse that had broken and displaced parts of the skeleton.
“Thus the flowstones do not date the skeleton,” says Clarke.
“In 2015, cosmogenic isochron dates using 26Al and 10Be were published in Nature, showing that the age of the actual breccia containing the skeleton dates back ca 3.67 million years. This is consistent with the original age estimates of around 3.5 million years that were proposed based on the low stratigraphic position of the deposit within the cave.”