In 2015, scientists announced an earlier time frame than previously estimated for the lifetime of an early proto-human dubbed Little Foot – as much as 3.67 million years ago. The nearly complete fossilized skeleton of the small Australopithecus creature was found in Sterkfontein Cave in South Africa in the 1990s.

Age estimates of the fossil have varied greatly over the years, but new dating methods have allowed a more precise estimate. The accuracy of methods used to date the fossils and stone tools found in Sterkfontein Cave previously have been called into question.

Live Science, quoting one of the researchers , said Australopithecines, including the famous Lucy of 3.2 million years ago, are thought to be the direct ancestors of Homo sapiens .

Australopithecines lived between 4.1 million and 2.9 million years ago. The lineage of humanity, Homo, originated about 2 million years ago, it’s estimated.

‘It was impossible to fit Little Foot into the human family tree with any certainty because “ever since its discovery, the age of Little Foot has been debated,” said lead study author Darryl Granger, a geochronologist at Purdue University in West Lafayette, Indiana. ‘If researchers can figure out when Little Foot arose, they might be able to better pinpoint which Australopithecus species and which part of Africa ultimately gave rise to Homo,’ Live Science reports.

In the same cave, scientists found what they believe are stone tools dating back as many as 2.4 million years. They believe these tools were made by a later, more advanced species, possibly Homo habilis .

The skull of Little Foot, a proto-human found in the 1990s (University of Witwatersrand photo)

“The cave infills at Sterkfontein contain one of the richest assemblages of Australopithecus fossils in the world, including the nearly complete skeleton StW 573 (‘Little Foot’) in its lower section, as well as early stone tools in higher sections. However, the chronology of the site remains controversial owing to the complex history of cave infilling,” the researchers wrote in their article (PDF link) in the journal Nature.

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The contrast in the tools used by humanity’s ancestors and found in the cave and the tools used to estimate dates of the fossilized remains and Olduwan culture tools is striking.

On the one hand you have a simple quart cobble used as a tool by pre-human species, possibly Homo habilis , about 2 million years ago (see below).

(Photo by the University of Witwatersrand)

On the other hand you have an accelerator mass spectrometry facility used to estimate ages of Little Foot and the tools by analyzing the decay of radioactive isotopes elements of aluminum and beryllium:

Screenshot of YouTube video showing scientists discussing their accelerator mass spectrometer that is dating layers of earth around fossils and tools in Sterkfontein Caves in South Africa.

The striking contrast in the complexity of the tools says a lot about how much more advanced modern humans are than our early ancestors, whose skulls even look primitive as compared to Homo sapiens (see the photo of Little Foot’s skull at the top of the article and of the Homo habilis skull below).

The capacity of Homo habilis skulls (above) averaged 640 cubic centimeters. Adult human skulls average 1130 cubic cm. Researchers said Homo habilis may have been using tools in Sterkfontein Cave about 2 million years ago. ( Wikimedia Commons )

“ ‘Little Foot’ is the nickname given to a nearly complete Australopithecus, or proto-human, fossilized skeleton found in the 1990’s by Professor Ron Clarke of the University of the Witwatersrand in the Sterkfontein cave system,” reports Popular Archaeology . “Assigning it to a new species he called Australopithecus prometheus , Clarke has been painstakingly excavating it over the years from the hard, cement-like breccia encasing it within the caves. Its dating by various dating methodologies at different times have yielded significantly differing dates, causing confusion and skepticism within the scholarly world regarding its true age. The efforts have been in part complicated by the dating of flowstones within the deposits that have shown young ages, in contrast to the surrounding deposits, which have shown much older dates.”

Researchers using the latest technology, including a technique applied first in mid-2014, showed that Little Foot, so-called for its diminutive stature, is 3.67 million years old. That is 1.17 years older than some of the 2.2 million-year-old flowstones that surround filled in later around parts of its fossilized skeleton. Another study had estimated the fossil to be 4 million years old.

The new dating methods were used in Purdue University’s PRIME lab .

Scientists said Australopithecus prometheus “poses new questions about the diversity, geographic spread, and relationships of early hominid species in Africa.”

The dates show Little Foot lived around the same time as Australopithecus afarensis of Ethiopia and Tanzania, though they are shaped differently.

“Little Foot, however, differed from afarensis in its morphology [body shape], with similarities to the flat-faced Paranthropus with its bulbous cusped cheek-teeth. It also differed from another well-known Australopithecine species called Australopithecus africanus, whose fossils were also found at Sterkfontein, and who was generally smaller,” Popular Archaeology states.

The researchers estimated dates of a quartz tool of the Olduwan culture found in higher-level sediments to be about 2.18 million years old. They think the stone cobble was a tool because hominids had to transport it into the cave from another location. It and other Olduwan tools found in the cave “shows that South Africa’s Cradle of Humankind was home to tool-making hominids by 2 million years ago or earlier……a much earlier age for tool-bearing hominids than previously anticipated in this part of Africa,” the University of Witwatersrand reported . Researchers from that university are studying the cave too.

Researchers said the tools were likely made by an early line of human species, possibly Homo habilis , which dates back 2.4 to 1.8 million years in eastern and southern Africa.

After 20 years of painstaking work, the skeleton was finally freed from the stone that enveloped it and was put on display for the first timein South Africa at the end of last year.

Featured image: Little Foot skull still in place in the Sterkfontein cave. ( Wikimedia Commons )

By Mark Miller