A slew of ground-breaking research has found that a controversial skeleton may belong to a new species of ancient human.

'Little Foot', a hominin which lived 3.67 million years ago, was an entirely different species than anything we have ever seen before, according to scientists.

Four scientific papers, which are yet to be peer-reviewed or published, claim the skeleton of an elderly female with a crippled left arm proves she does not belong to any known category.

She was also discovered to have legs longer than her arms, a trait associated with the evolution of modern man as it favours bipedalism - walking on two legs.

Other studies on the remains have found she had an exclusively plant-based diet and stood at just over four foot tall (130 cm).

The proposed name of the species is Australopithecus prometheus.

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'Little Foot', a hominin which lived 3.67 million years ago (pictured), was an entirely different species than anything we have ever seen before, according to scientists

Little Foot, of the Hominid species Australopithecus prometheus, roamed the plains of Africa around 3.6 million years ago, while Lucy, another early human ancestor, lived on the continent 3.2 million years ago. Modern humans wouldn't evolve for at least another 3 million years

The skeleton was first discovered in the 90s in South Africa and was first categorised as Australopithecus, a group of hominins to which the famous fossil 'Lucy' belongs.

Dr Ronald Clarke of the University of the Witwatersrand in Johannesburg has claimed for two decades that this is incorrect and Little Foot does not belong to any known species.

He claims she is a member of a new species, which he calls A. prometheus - a grandiose name stemming from the Greek titan Prometheus who crafted mankind from clay.

Dr Clarke is either the lead author or a corresponding author on all four studies.

He told New Scientist: 'I've spent 20 years getting this skeleton, finding it in the rock in the deep darkness of the cave, locating every bone, and then cleaning it sufficiently so we could identify them in the cave, undercutting them, bringing them out in blocks, cleaning them, reconstructing them.'

He used an air scribe to painstakingly remove the remains without the fragile bones flaking away.

DATING LITTLE FOOT Stone tools found at a different level of the Sterkfontein cave also were dated at 2.18 million years old, making them among the oldest known stone tools in South Africa In 2015, a team used Purdue's PRIME Lab's powerful accelerator mass spectrometer and a new detector, called a gas-filled magnet detector, to measure the radioisotopes. 'We succeeded in our measurement, but we were surprised the dates were so old,' Granger said. 'We double-and triple-checked our results, running the measurement again and again.' The gas-filled magnet creates a different charge on the two radioisotopes and throws the magnesium-26 on a different path with a curvature that misses the detector. This lowers the magnesium ratio and increases the aluminum-26 count in the sample that makes it to the detector, which results in a much smaller margin of error in the measurement. The gas-filled magnet detector was originally to be used to analyze samples of solar wind collected by the Genesis spacecraft. Unfortunately, the space capsule carrying the samples crashed in 2004 on its return to Earth. The crash delayed analysis of the Genesis samples, but Caffee continued to build the detector and it was completed the summer of 2014. Caffee has since used it to perform analysis for other projects, including those from the Sterkfontein site. 'Only a few detectors of this kind exist in the world,' Caffee said. Advertisement

The skeleton dates back 3.6 million years. Four scientific papers, which are yet to be peer-reviewed or published, claim the skeleton of an elderly female with a crippled left arm proves she does not belong to any known species of human ancestor

Robin Crompton of the University of Liverpool worked on another paper, also in conjunction with Dr Clarke, and found some early hominins were large-bodied and had hindlimbs longer than forelimbs

The remains of Little Foot were first found in the Sterkfontein caves near Johannesburg in 1994.

The affectionate nickname for the fossil, formally known as StW 573, was obtained when a scientist used the term to describe the petite bones compared to the larger hominins known to exist at that time.

Travis Pickering of the University of Wisconsin-Madison in the US, led one of the four studies and discovered that Little Foot suffered with a severe injury.

Her left forearm created 'bilateral asymmetry' as her left limb became deformed with respect to her right.

Her left forearm created 'bilateral asymmetry' as her left limb became deformed with respect to her right. The lower arm became bowed and the researchers say that 'these curvatures resulted from a fall onto a hyperextended, outstretched hand'

Little Foot was also discovered to have legs longer than her arms, a trait associated with the evolution of modern man as it favours bipedalism - walking on two legs. Other studies on the remains have found she had an exclusively plant-based diet and stood at just over four foot tall

FINDING LITTLE FOOT In 1994, Ron Clarke, a paleoanthropologist from the University of the Witwatersrand in South Africa, discovered the skeleton of Little Foot in Silberberg Grotto at Sterkfontein. It is believed that she fell down a narrow shaft in the Sterkfontein Caves, leaving behind a nearly complete skeleton. Dr Clarke discovered her remains - four foot bones - in 1994. Then in July 1997, he and Stephen Motsumi and Nkwane Molefe, located the position of the end of the skeleton's shin bone in the Sterkfontein caves. In July 1997, Dr Clarke and Stephen Motsumi and Nkwane Molefe (pictured), located the position of the end of the skeleton's shin bone in the Sterkfontein caves Advertisement

The lower arm became bowed and the researchers say that 'these curvatures resulted from a fall onto a hyperextended, outstretched hand'.

Dr Pickering and his colleagues say it was unlikely that the the fall was from a significant height and might have occurred when she was a child.

Robin Crompton of the University of Liverpool worked on another paper, also in conjunction with Dr Clarke, and found some early hominins were large-bodied and had hindlimbs longer than forelimbs.

This, they say, would have had a dramatic impact on how the individual would move.

It was effective for walking longer distances but would have made the animal less efficient at climbing and Little Foot would have been unable to carry things well while walking.

Dr Crompton writes in the abstract of the paper: 'This, and other evidence presented herein, suggests there are two pelvic girdle morphs at Sterkfontein, supporting Clarke (2013) in his recognition of a second species, A. prometheus, containing StW 573 [Little Foot].'

Research led by Dr Clarke himself analysed the skull of Little Foot and found the remains again backed the theory of a new species.

'There are many, many differences, not only in the skull but also in the rest of the skeleton,' he says. They include a flatter face than A. africanus, and larger teeth with a big gap between the upper canines and incisors,' he said.

'A. africanus was more omnivorous,' says Dr Clarke.

A further study looked at the relationship between the cave where little Foot was found and the skeleton.