Human thigh bones apparently make excellent weapons in close combat

Ancient daggers carved from femurs were pretty fierce.
Bone daggers of the Sepik watershed, New Guinea. (a) Human bone dagger attributed to the Upper Sepik River (b) Cassowary bone dagger attributed to the Abelam people. Hood Museum of Art, Dartmouth College

It turns out human bones, especially thigh bones, were prized by New Guinean warriors as materials which could be carved into exceptionally strong, fierce daggers.

Until the 20th century, males in New Guinea often used bones, particularly femur bones acquired from large birds, to carve out sharp tools which served as both combat weapons as well as symbols of prestige and respect in the community. However, in a new study published in the journal Royal Society Open Science, a team of American researchers find that bone daggers fashioned from human thigh bones actually made for the strongest type of weapons, and were by extension often viewed by members of the community as symbols of status and notoriety.

“[Paupan] men [of New Guinea] made human bone daggers differently,” says Nathaniel Dominy, a professor of anthropology at Dartmouth College in New Hampshire and the lead researcher of the new study. “They made them to be stronger—which we interpreted as a deliberate effort to preserve the tremendous social prestige associated with possessing a human bone dagger.”

Dominy and his colleagues began their study based on the vast collection of of human bone daggers housed at Dartmouth, one of the largest in the United States. He stumbled across a series of daggers in the collection that were about 12 inches long, made from the leg bones of both cassowaries (flightless birds native to New Guinea and northeastern Australia) and humans, intricately carved and ornately designed. While there were a few accounts from missionaries in the late 19th and early 20th century about the daggers, there was a great dearth in anthropological examination about how they were made and used, and what role they played in cultural practices—and most importantly, why some were made from human thigh bones and some were made from cassowary shin bones. “We saw an opportunity to compare the two types, human versus cassowary, because we knew we would have a sufficient sample size.”

Bone daggers
Three-dimensional reconstructions of each dagger in the present study. Dominy et al

Guinean warriors fought in close-quarter combat, with the aim of killing opponents quickly with a stab to the neck, into a main artery, followed by a twist to tear out the throat and potentially break the neck. “The sole purpose of the bone daggers was to function as weapons,” says Dominy. “You stabbed men during hand-to-hand fighting or you stabbed prisoners to disable them from escaping.”

But the daggers needed to be strong and hardy. “Once a dagger is broken,” says Dominy, “then it loses both its symbolic strength and practical utility”—hence, one of the reasons human bones were viewed as a prime material for carving daggers.

The research team took CT scans of five cassowary-bone daggers and five human-bone daggers, analyzing their density and figuring out which versions would make for better weapons. They also ran some tests and found that the cassowary daggers could withstand about 44 pounds of force, while human daggers proved about twice as strong.

“Bone is pretty tough, due to its composition of both organic proteins that give it fracture toughness and tensile strength, and inorganic mineral that makes it hard,” says R. Dana Carpenter, a professor of mechanical engineering at the University of Colorado Denver. “As a comparison, stone weapons would be harder but more brittle. Wooden weapons would be tough, but not as hard, in general.”

And it seems Guinean warriors prized the human femur above other materials thanks to the thick, dense bone that makes up its shaft. The cassowary tibiotarsus is broader, and the resulting carved dagger will end up with a flatter cross-sectional shape. “It only has substantial bending strength in one bending direction,” says Carpenter, “while the human femur dagger has a higher resistance to bending in many different directions.”

Both human femurs and cassowary tibiotarsuses exhibited the same sort of tissue stiffness, so the advantage of the human bone really came down to anatomical geometry, the researchers found. Guineans, in fact, took care to specifically carve cassowary bones into weaker weapons, probably to ensure that human bone daggers—already rarer—maintained their higher value and superior social clout.

Besides the physiological differences, the researchers also unearthed some cultural reasons why human remains were held in higher esteem than bird bones. Guinean warriors would make weapons from the bones of ancestors or respected community members who passed away, believing they would imbue the dagger—and the person wielding it—with spiritual benefits and strengths.

Still, it would be a mistake to throw too much shade at cassowaries. These fruit-eating, flightless birds are dangerous animals in their own right, possessing claws that can measure about 12 centimeters long, and a running speed of up to 31 miles per hour. Their sharp kick is more than capable of chopping down even a large predator.

The researchers are still hazy on whether the cassowary bone could prove to be a better tool in the actual act of stabbing and twisting during a fight, were it carved in a more optimal fashion. Carpenter says he and the team would like to do additional mechanical testing using 3D printed copies of the daggers. “We can’t break the beautiful museum pieces,” he says, “but we have computer models of each dagger, so this type of test may be feasible.” Sounds like a reasonable approach to taking a stab at those questions.