Paranthropus boisei, an African hominid that lived between around 2.3 million and 1.2 million years ago, may have strong-armed its way into stone-tool making with a deft touch.
That’s the implication of the first hand, arm and shoulder fossils discovered from the same P. boisei individual, say paleobiologist David Green and colleagues. The fossils suggest that this extinct species combined powerful arms suited to tree climbing with grasping hands capable of fashioning stone implements, the researchers report in the April Journal of Human Evolution.
P. boisei, a distant cousin to modern humans, lacked a thick, powerfully gripping thumb characteristic of its hominid contemporary, Homo erectus (SN: 3/24/15), a prolific maker of sophisticated stone tools. But the newly described hand bones suggest that P. boisei gripped well-enough to make and use simple stone and bone tools, just as other members of the human evolutionary family may have as early as 3.3 million years ago (SN: 5/20/15). That’s long before the emergence of the Homo genus, which appeared around 2.8 million years ago. But reports of tool-making before Homo originated are controversial.
“This is the first evidence that creatures that were almost certainly not our direct ancestors could have made tools,” says paleoanthropologist Bernard Wood of George Washington University in Washington, D.C. “So we can no longer assume — nor should we ever have assumed — that only Homo could make tools,” says Wood, who was not involved with the new research.
It’s tempting to argue that only H. erectus, which had a brain approaching twice the average size of P. boisei’s, could have made teardrop-shaped, double-edged hand axes that date to around the same time as the two hominids. Those tools demanded more skill and planning than earlier, simpler cutting implements. But the case is not closed, says Green, of Campbell University School of Osteopathic Medicine in Buies Creek, N.C. “We’ll need to find tools that can be confidently associated with P. boisei and assess its technical abilities before assuming that H. erectus was the superior toolmaker.”
Excavations and surveys from 2004 to 2010 at Kenya’s Ileret site produced the new P. boisei finds. Fossils were found in sediment that dates to between about 1.53 million and 1.51 million years old. Previously excavated 1.5-million-year-old footprints at Ileret may have been left by H. erectus or P. boisei (SN: 4/16/12).
A large male skull discovered in 1959 is the best-known P. boisei fossil. Dubbed Nutcracker Man, the individual has wide cheekbones that project forward and a bony crest atop its braincase that once anchored huge chewing muscles. Nutcracker Man may have eaten mainly grasses and flowering plants called sedges (SN: 5/2/11).
Suggestions that another member of the Paranthropus genus, P. robustus, crafted stone tools, based on isolated finger bones unearthed in South Africa’s Swartkrans cave complex, go back more than 30 years (SN: 5/28/88). Parts of two arm bones and two leg bones from an adult male P. boisei have turned up since then at Tanzania’s Olduvai Gorge (SN 12/10/13). But the Ileret discoveries offer the first look at bones from throughout a P. boisei individual’s upper limb. As a result, researchers can more confidently reconstruct what types of arm and hand movements that hominid could perform.
Stone artifacts are abundant at ancient Homo sites, a sign that our genus relied far more heavily on toolmaking than P. boisei did, says biological anthropologist Neil Roach of Harvard University, who wasn’t involved in the research. No stone artifacts have been clearly linked to P. boisei fossils.
Intriguingly, Roach adds, the Ileret fossils are relatively large and thick, suggesting that P. boisei was more athletic and physically active than typically presumed for a hominid species that, unlike H. erectus, probably did not eat meat.