Discovery of fossilized hand may unlock a 1.5-million-year-old mystery
Some sixty years after her grandmother discovered “Nutcracker Man,” Louise Leakey unearths his long-lost hand—reviving a family debate about ancient toolmaking.
National Geographic Explorer-at-Large Louise Leakey grew up hearing about the July morning in 1959 when her grandmother—paleoanthropologist Mary Leakey—discovered a 1.8-million-year-old hominin skull in Oldupai Gorge (originally misnamed Olduvai) in Tanzania.
After spotting fossilized teeth lodged in a rock, Mary drove straight back to camp to tell her husband Louis Leakey, who had stayed behind that day because he felt ill. She yelled “I've got him! I've got him! I've got him!” Louis recalled in a September 1960 article he wrote for National Geographic.
“Got what? Are you hurt?” he asked.
“Him! The man! Our man.”
After nearly three decades scouring the slopes of the gorge, the Leakeys and their colleagues finally found what they thought was the maker of the stone tools they first uncovered at the site in 1931. Today, the hominin is known as Paranthropus boisei, but back then it was nicknamed “Nutcracker Man” in the newspapers because of its impressive jaws and molars.
Generations of scientists have since debated whether P. boisei really could have made and used stone tools, including Louis and Mary’s own son Richard who doubted that the early hominin was a toolmaker. One important clue that could settle the debate has been missing all this time, however: a hand unambiguously linked to P. boisei.
That was, until now.
In a paper published Wednesday in Nature, Louise Leakey and her colleagues announce the discovery of a 1.5-million-year-old hand belonging to P. boisei. The hand was found together with identifiable parts of a skull, teeth, feet and various other bones, meaning the hand was "unambiguously associated" with P. boisei, they say. Leakey’s team excavated the new fossils in Lake Turkana, Kenya, between 2019 and 2021, some 60 years after her grandmother first found the hominin. The discovery also came in time for her father, Richard, to marvel at it before his death in 2022.
“He was thrilled!” Leakey says. “He thought this was a hugely significant discovery, because we finally can see what Paranthropus' hands look like.”
The finding suggests that P. boisei had hands that were both dexterous and powerful, providing strong evidence the "Nutcracker Man" was well-equipped for making and using tools.
(Richard Leakey, trailblazing conservationist and fossil hunter, dies at 77)
“The authors make a compelling case that this individual would have been able to grip rocks with sufficient precision to have been able to make and use simple stone tools,” says David Strait, a paleoanthropologist at Washington University in St. Louis, who was not involved in the paper. “This is arguably the best evidence yet found indicating Paranthropus was a toolmaker.”
However, the researchers themselves caution that they cannot say for certain whether P. boisei did in fact use tools or make the tools found at the site. “All we can say is that they would have been able to,” says Carrie Mongle, a paleoanthropologist from Stony Brook University and the lead author of the new study. Though paleoanthropologists had previously found hand bones in East Africa, “it’s just very difficult to know what species they are,” says Mongle.
Nevertheless, the new anatomical evidence that Louise Leakey’s team found restores an idea that her grandfather and father had mostly abandoned back in the 1960s.
Decades-old toolmaker debate
Louis Leakey was initially convinced that P. boisei “clearly fashioned his own tools,” as he argued in his 1960 National Geographic article.
Since this was the first hominin Louis and Mary had found at the site, “he had nothing else that he could choose from,” as the potential tool maker, says Louise Leakey.
Louis suspected P. boisei (which he called Zinjanthropus boisei) needed to use stone tools because its incisors and canines—teeth used for cutting and tearing—were blunt and small, rendering them ineffective for ripping the skin or fur from small animals.
“I know this for a fact,” Louis wrote, “for as an experiment I have tried to strip the hide from a hare with my own teeth and fingernails, and I was not able to do it.”
“True Louis style,” says Louise.
But she adds that even Louis had his doubts. “I don't think he was particularly happy with the brain size to call it a tool user,” she says.
In early 1964, the Leakeys and their team found another hominin, with skull bone fragments suggesting it had a much larger brain. Louis called it Homo habilis, or the “Handy Man.” In an article published in Nature a couple of months later, Louis and colleagues concluded that while it was possible that both species had made stone tools, Homo habilis was the advanced toolmaker and Paranthopus boisei, he said, may have been just an “intruder” in the area.
In just a few years, Paranthropus boisei had gone from earliest-known toolmaker to probable imposter.
Louis’ son Richard and his wife Meave, also a paleoanthropologist, then moved the research project around 500 miles north from Tanzania to the eastern shore of Lake Turkana in northern Kenya. There, they discovered in 1969 another P. boisei skull (which they called Australopithecus boisei) and some stone tools. Like Louis, Richard was skeptical of the connection.
(Inside Richard Leakey's discovery of an ancient human ancestor skull—the same his parents chased)
“There were our tools, the oldest ever found. Who had made them? Not Australopithecus boisei, I felt,” Richard wrote in National Geographic in 1970.
In contrast to what his father had written a decade earlier, Richard came to his conclusion, he wrote, because P.boisei “possessed a massive jaw and huge grinding teeth, implying that he had adapted to suit a predominantly vegetarian diet. He would have had little need to devise cutting tools.”
Several other human relatives also lived alongside P. boisei in this area of Eastern Africa about one to two million years ago, including Homo habilis, and Homo erectus. Like his father, Richard thought a different hominin made the tools.
“It's a very difficult one to pinpoint,” says Louise, “with all these different hominins there.”
The only way forward to answering such questions definitively is to do what the Leakeys have always done: to keep looking. And now, they have finally found the P. boisei hand—one that looks like it could have used the tools.
The new discovery by Louise Leakey and Mongle's team supports the “hypothesis that Homo did not have the monopoly of stone tool making and use,” says Zeresenay Alemseged, a paleoanthropologist from the University of Chicago and a National Geographic Explorer.
Human-like hands, gorilla-like grip
After carefully piecing the remaining parts of the new hand together, the team behind the new paper found its proportions to be comparable to modern humans, with a rather long thumb and broad fingertips that would help with gripping. A hand like that could have been used to make or manipulate tools, says Mongle, though it wouldn’t have had the dexterity to pinch with precision.
“If you look at the shape of the bone where the thumb meets the wrist, humans are really unique in having a very flat surface there, which we think allows for even more freedom of movement,” she says. The new fossil, by contrast, has a smaller, more curved joint like that of apes.
Another interesting aspect of the hand is its sturdy finger bones and what they reveal about the ‘flexor’ muscles that P. boisei used to curl its fingers. You can feel those muscles contract if you touch the bottom or middle part of one of your fingers while flexing it. But what you won’t feel is what P. boisei had: strong bony muscle attachments.
The muscles on the pinky side of the palm that you can feel bulging up when you tighten your fist were also well-developed, according to Mongle. “In humans, you see these muscle attachments in the palm of the hand as a faint line. In P. boisei, they’re like a hook that comes out,” she says. “So, you can imagine this individual’s grip strength would have been incredible.”
The researchers speculate that P. boisei may have also primarily used its strong grip to grab, twist, and tear sturdy plants as modern gorillas do. But not everyone is convinced this would be the most obvious explanation for why the hands look the way they do.
“To me, it’s hard to explain those really strong muscles and powerful hands just by the amount of strength needed to break and manipulate plants,” says Tracy Kivell, a paleoanthropologist at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, who was not involved in the study but has done a lot of work comparing fossil hominin hands to those of modern humans and apes.
(Did ancient ‘hobbit’ humans create these million-year-old tools?)
Though she agrees P. boisei’s hands are like those of gorillas, she thinks those strong hands may also have been an adaptation for climbing rather than tearing away at sturdy plants, which she details in a related article published alongside the new paper.
Mongle and Leakey don’t think climbing likely explains the hand’s anatomy. They say P. boisei did not spend a lot of time in the trees, since its lakeshore habitat probably did not have many. In addition, tree-climbing apes have long, curved fingers, which the fossilized hand clearly didn’t. Finally, they add, the feet bones that they also found look more fit for walking upright than latching to trees.
Mongle, Leakey and Kivell plan to collaborate on a future study looking at the internal structure of the hand bones to help provide more information on how they were used.
A Leakey legacy, with lots of help
In the last 20 years, the fieldwork became a lot more intense after Richard Leakey founded the Turkana Basin Institute in northern Kenya, says Louise. “It’s transformed how we do the science, but also the rate of discovery,” she says. “We’ve got quite a few in the pipeline. We’ll be talking again soon, I’m quite sure.”
(Inside the hunt for the other humans)
As Louise Leakey continues her family’s legacy of discovery, she credits much of their achievements to the local collaborators who’ve worked alongside the Leakeys for generations. In addition to an international group of researchers—including her mother Meave—the new paper is coauthored by many members of the field team.
“The team of fossil hunters, they’re all drawn from local communities where we work,” says Louise. “They’re integral to the success of these discoveries. They’re really good, very skilled.”
Reflecting on the Leakey legacy, Louise wonders what her grandfather Louis would have made of this hand discovery. “It’d be great if he could come back today,” she says. “I’d love to have his view on all of this. Wouldn’t it be fun?”
