Experts have been puzzled by recently discovered fossils from the hand of an extinct human relative, Paranthropus boisei. They have been surprised by a mix of human-like and gorilla-like traits in the fingers.
In the journal Nature, researchers describe the set of 1.5-million-year-old fossils from a site in Kenya that includes the first unambiguous Paranthropus hand bones identified in the fossil record. They are also a very rare example of a relatively complete set of hand bones from this time.
The first example of Paranthropus was discovered in South Africa by Dr Robert Broom in 1938. Its name means “beside man” and reflects the fact that it shared a direct ancestor (known as Australopithecus) with our own genus, Homo, but existed alongside the early human lineage. Broom’s fossils belonged to the species Paranthropus robustus.
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The species Paranthropus boisei, on the other hand, was first discovered in Olduvai Gorge, Kenya, by Mary and Louis Leakey in 1959. Its massive mandible and teeth led to its nickname: the Nutcracker Man.
The very molarised teeth (where a non-molar tooth takes on the appearance of a molar) indicated a possible diet of tough and fibrous foods – almost certainly consisting of vegetation – that required extensive chewing.
Paranthropus was a bipedal hominin, like representatives of our own lineage, with a similar body size. It also lived in similar habitats to early Homo. Yet it became extinct around 800,000 years ago.
Inevitably, these two hominin lineages have been compared in every possible manner to identify which traits ensured Homo’s survival. Homo’s persistence has been attributed to its large brain, small teeth, and meat-based diet.
Paranthropus, on the other hand, with its large teeth and a smaller brain, is often cast as an evolutionary “also-ran” – not quite clever or adaptable enough to persist in a changing world.
However, there was little real evidence for concrete differences in how Paranthropus used its body or its surroundings. Until now.
The new fossil set from Koobi Fora, on the eastern shores of Lake Turkana in Kenya, shows that Paranthropus boisei was not clumsy or poorly adapted to its lifestyle. The remains, dated to around 1.52 million years ago, include a partial skeleton with both hand and foot bones found alongside unmistakable P. boisei jaws and teeth.
For the first time, we can connect this species’ massive chewing apparatus with the limbs and hands that helped it function in the ancient landscape.
The fingers are, in many respects, more like gorillas than humans, but the feet are very similar to Homo feet. In fact, the foot shows that P. boisei was an efficient biped, walking on arched, rigid feet that resemble our own more closely than those of earlier species such as Australopithecus afarensis.
The big toe was aligned with the others, and the joints show the same upward tilt – called dorsal canting – that allows modern humans to push off powerfully when walking or running. A twisted third metatarsal bone formed a transverse arch, the architectural feature that stiffens the human foot and turns it into a spring for energy-efficient movement.
The new find suggests a mix of both advanced and primitive features. It paints a picture of a creature capable of traversing the mixed open habitats of East Africa on two legs, moving confidently between feeding areas and perhaps even carrying food or simple tools. The powerful hands may have been used to forage for food, which required a strong grip.
There may be an argument that Paranthropus was pulling itself into the trees. Until now, Paranthropus has not been thought of as a climber, nor an animal associated with particularly dense tree cover. It was thought that cooling climates and thinning forests led to bipedalism in both Homo and Paranthropus.
Yet there are clear differences with Homo. The big toe of P. boisei was shorter than ours, hinting at a slightly different gait – perhaps a slower, heavier stride. The smaller toes were straighter and stiffer than those of apes but not as refined as in Homo sapiens. This mosaic anatomy shows that upright walking had already been perfected in several human relatives, even if each did it in their own way.
The foot of P. boisei demonstrates that by 1.5 million years ago, bipedalism was a shared foundation rather than a unique advantage. Both Homo and Paranthropus walked tall; their evolutionary paths diverged not in locomotion but in lifestyle.
While Homo relied increasingly on brainpower, tools, and cooperation, Paranthropus doubled down on strength and chewing muscle. One lineage adapted to flexibility, the other to endurance – and in the end, only one survived.
But the discovery also softens the old story of triumph and failure. Paranthropus boisei wasn’t a “failed” hominin relative. It was a successful species in its own right, perfectly adapted to its ecological niche for well over a million years.
The new fossils remind us that human evolution wasn’t a straight march of progress but a branching bush of experiments – some favouring brains, others brawn, all walking upright beneath the same African sun.
Sally Christine Reynolds, Associate Professor in Hominin Palaeoecology, Bournemouth University
This article is republished from The Conversation under a Creative Commons license. Read the original article.
