Humans have been modifying their bodies for millennia. In some cultures, alterations like foot binding, neck lengthening and tattoos are related to class, beauty ideals or spirituality. But new research suggests the Hirota people of ancient Japan had a more practical reason for modifying their infants’ skulls: to facilitate trade.
The study, published in the journal PLOS One, argues that the Hirota people purposefully distorted their children’s skulls. Previously, researchers were unsure whether the deformations were the result of “an unknown natural process,” writes Live Science’s Harry Baker.
The Hirota thrived between the third and seventh centuries, says lead author Noriko Seguchi, a biological anthropologist at Kyushu University in Japan, in a statement. Archaeologists began studying Hirota skeletons in 1957, when a large burial site was discovered on Tanegashima Island in the country’s Kagoshima Prefecture. Examining the skeletons, researchers found that their skulls were both short and flat at the back, suggesting the bones had been modified.
Seguchi’s team analyzed the skulls’ shapes by examining images and three-dimensional scans of their outlines and surfaces. Researchers then compared their findings with cranial data from archaeological sites elsewhere in Japan. They found the Hirota skulls possessed “distinct cranial morphology” and varied considerably from those of the Yayoi and Jomon, two ancient Japanese populations that lived around the same time, Seguchi says. The results led the team to conclude the crania were deliberately shaped before death.
Intentional cranial modification relies on the pliability of a newborn baby’s skull, which is not fully formed at birth. Gaps between cranial bone plates provide a window of opportunity to decide the skull’s shape before it finishes developing; ancient peoples around the world seized this opportunity to mold the heads of their young. The Maya, for example, flattened babies’ skulls by affixing their heads to a flat surface similar to a cradleboard. This procedure may have been designed to protect the child’s soul, wrote Discover magazine’s Eric Taipale in 2022. Others, like a group of Neanderthals who lived 45,000 years ago, practiced cranial modification because they believed it improved their chances of survival, Popular Science’s Laura Baisas reports.
The motivations behind the Hirota people’s tradition are more mysterious. But researchers were able to eliminate some possibilities in their analysis and propose a new explanation. Both male and female skulls showed signs of modification, suggesting the practice wasn’t part of gender-based customs. Also, the remains were interred with few indicators of differing social class or wealth. In total, 90 percent of the burials “were associated with funeral goods, such as shell ornamental products,” according to the study.
More than 44,000 shell ornaments—including bracelets, plaques and beads—have been found at the Hirota burial site, wrote Richard Pearson in Ancient Ryukyu: An Archaeological Study of Island Communities, his 2013 book about a network of shell trading on islands of Japan. The Hirota people, like other island communities, relied heavily on shellfish for sustenance and bartering. They likely harvested their own shells, Pearson writes, and acquired others from neighboring groups. The new study posits that intentional cranial modification among the Hirota people may have been related to this trading network.
“The researchers hypothesize that the Hirota people deformed their crania to preserve group identity and potentially facilitate long-distance trade of shellfish, as supported by archaeological evidence found at the site,” the statement says.
The Hirota population’s particular skull shape remains unique to their community, as no other crania in the Japanese archipelago have shown similar morphology. But their use of cranial modification to differentiate themselves from other island peoples was far from unique among the many prehistoric humans who shaped their skulls.
“Our findings significantly contribute to our understanding of the practice of intentional cranial modification in ancient societies,” says Seguchi in the statement. “We hope that further investigations in the region will offer additional insights into the social and cultural significance of this practice in East Asia and the world.”