If there’s one thing that paleoanthropology has revealed time and again, it’s that many renditions of ancient human species preceded us modern humans today.

While Neanderthals and even Homo erectus have become fixtures in the human origin story, a lesser-known predecessor appears to predate all the others: Homo habilis.

H. habilis has been called the oldest known member within the Homo genus, though not without controversy and ongoing debate.

By many scientists’ accounts, the species was likely walking upright on Earth more than 2 million years ago — which is to say, nearly 2 million years before Homo sapiens even appeared on the evolutionary tree.

Homo Habilis Meaning

The Latin name for this species, loosely translated as “handy man” or “able man,” alludes to a crucial characteristic that set it apart: dexterous hands.

Fossilized specimens have included human-like foot and hand bones, which suggests an ability to manipulate objects with precision. And, in fact, simple stone tools have been found near some of the earliest H. habilis remains identified by anthropologists.

An enlarged brain case also distinguishes this species from our more distant, early hominid ancestor Australopithecus — famously known for the 3-million-year-old Lucy specimen in Ethiopia.

Read More: The Australopiths: Our Ancient, Ape-like Forefathers

Homo Habilis Characteristics

H. habilis made its debut in the conversation of human origins in the early 1960s, after a series of landmark discoveries by anthropologists Louis S.B. Leakey and Mary Leakey, who were married.

With a team of researchers, the Leakeys were stationed at a dig in the Olduvai Gorge of northern Tanzania in the 1950s when they unearthed two unique teeth, followed later by a lower jaw and hand bones.

After combining and assessing their various specimens, they presented a picture that seemed to mix human-like features with characteristics also seen in the ape-like Australopithecus.

Read More: Humans Evolved From A Common Ancestor That Appeared 6 Million Years Ago

Credibility for a New Homo Species

Louis S.B. Leakey, alongside co-authors Phillip Tobias and John Napier, published the first paper on H. habilis in Nature in 1964.

That work addressed three key elements to meet the definition of Homo. They argued that their specimen had a bipedal gait, an upright posture and the ability to fashion simple stone tools.

The team had to modify the standing parameters for Homo brain size, since their specimen’s skull, which was thin and rounded, had a smaller braincase than Homo erectus and other early human species.

Subsequent discoveries have indicated that H. habilis likely had an average braincase capacity around 640 cubic centimeters (CC), compared to 440 CC in Australopithecus. (The equivalent in H. sapiens averages just over 1,300 CC.)

Other features seen in H. habilis specimens, including a relatively large facial skeleton with a flattened lower part and particularly long limbs, make it seem like an intermediate species between Australopithecus and H. erectus — though it may not be in direct succession.

Likely remains of the mysterious species have also now been found in northern Kenya, Ethiopia and South Africa.

Read More: What Did Humans Evolve From?

Incomplete Evolutionary Puzzle

In the words of paleontologist Bernard Wood, published in a 2014 Nature story, the discovery of this species “should remind us of how much we don’t know, rather than how much we do.”

Leakey’s findings in the 1960s certainly shifted the search for the earliest humans from Asia to Africa. But there may well be other Homo ancestors yet to be named and discovered. 

Notably, the world’s oldest known stone tools now appear more than 3 million years ago in the fossil record, which seems to be well before H. habilis. And scientists still aren’t sure what species created these tools.

If it was not Australopithecus, perhaps there is another handy predecessor to H. habilis waiting to be unearthed.

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