Who are the Hirotas?
The tiny island of Tanegashima lies about 50 kilometers south of Japan’s main landmass. It is well known as a launch site for space rockets, but it also yields ancient clues. Archaeologists uncovered remains from the 3rd to the 7th centuries on Tanegashima, including a large group belonging to the Hirota people who lived there for generations. The Hirota bore features that resembled the Ainu, Japan’s oldest known inhabitants, more than typical modern Japanese. Their faces showed pronounced brow ridges and upturned noses, and they were notably short for their time, averaging about 154 centimeters for men and 142 centimeters for women.
The most striking aspect, however, was the shape of their skulls. The back of the skull tended to be flattened, with the occipital and parietal regions especially broad. The flattening could be accidental, possibly arising from cultural practices or daily habits, but it also raised questions about intentional modification. In parallel traditions around the world, people have altered bone shape in childhood, but the Hirota case suggested a systematic pattern rather than a random tendency.
How were the skulls studied?
To get to the bottom of this, researchers compared Hirota skulls with those of other ancient Japanese populations. For preservation and precision, the bones were scanned and a highly accurate virtual 3D replica was created with less than 0.05 mm error. Using geometric analysis, they confirmed that the observed flattening extended beyond typical biological variation. Close inspection revealed grooves along the sagittal and lambdoid sutures, supporting the idea that the skull shapes were not merely incidental.
The Hirota skulls proved to be distinct from the patterns seen in the Yayoi and Jomon peoples who lived on the major islands of Japan. Across different time periods, Hirota individuals showed varying degrees of deformation, yet those buried in the same area and era displayed similarly flattened skulls. This points to deliberate alteration rather than random growth, suggesting a shared cultural practice among Hirota across generations. While some may connect such changes to particular trades or roles, none of these bones show clear signs of social stratification in the burials. Rich grave goods appear in many graves, but this alone does not establish a strict social hierarchy. The broader picture indicates that complex social structures emerged in Japan after agriculture, but the Hirota case does not fit a simple elite-versus-common pattern.
Why did they do it?
Skull modification was not unique to the Hirota. Similar traditions appeared elsewhere, including among elites in long-vanished Mesoamerican cultures where cranial shaping signaled status. Ancient writings describe beliefs that linked head shape to nobility or divine favor, signaling membership in higher social strata. However, this account requires careful interpretation, since direct evidence of social rank is not straightforward in Hirota burials. Some scholars propose that the modified skulls marked offspring from prominent families, while others suggest that the practice reflected broader communal identity. It is unlikely that such markings resulted from food production or village labor alone, given the absence of clear, pervasive social division in the cemeteries.
Historical descriptions from antiquity mention similar shaping practices among other ancient groups, sometimes framed by religious or cultural traditions. The key insight from the Hirota study is the combination of deliberate modification and strong group identity. It suggests that Tanegashima communities used skull shaping as a visual cue to distinguish friends from outsiders, reinforcing cohesion across distant trade networks and shared cultural practices. The evidence supports a view of the Hirota as a people who valued identity signaling and community reinforcement through a distinctive physical trait that endured through generations.