Tuesday, 26 Sep 2023

Parents on a Japanese island deformed their children's heads. No one knows why

An ancient civilisation deliberately deformed the shape of children’s skulls – but no one knows why.

The Hirota people, who lived on the southern Japanese island of Tanegashima around 200 CE to 600 CE, had significantly shorter heads that were flatter on the back.

Until now however, archaeologists were not sure if the shape was a natural deformity or deliberate. 

As any new parent knows, babies’ heads are notoriously soft when they’re born. This is due to gaps between the large bones of the skull enabling ‘cranial pliability’ – a quirk which evolved to better help squeeze such a large head through the birth canal.

Due to this pliability, parents have long been able to shape their children’s skulls by binding infants’ heads with cloth or pieces of wood, often elongating them – a practice seen in many civilizations throughout history, even as far back as the Neanderthals.

Initially the practice may have been unintentional, given how easily the skull can be moulded, such as by leaving a baby resting on their back for long periods of time. However, it became a deliberate practice, and continued into modern times, witnessed in Vanuatu and other cultures in recent years.

‘One location in Japan that has long been associated with cranial deformation is the Hirota site on the Japanese island of Tanegashima, in Kagoshima Prefecture,’ said co-author and team leader Dr Noriko Seguchi, from Kyushu University. 

‘This is a large-scale burial site of the Hirota people who lived there during the end of the Yayoi Period, around the 3rd Century CE, to the Kofun Period, between the 5th and 7th Century CE.

‘The site was excavated from 1957 to 1959 and again from 2005 to 2006. From the initial excavation, we found remains with cranial deformations characterised by a short head and a flattened back of the skull, specifically the occipital bone and posterior parts of the parietal bones.’

The occipital bone is the large round bone at the back and base of the bead. There are two parietal bones, one each side which form the roof and sides of the skull.

To further understand the deformations, the team analysed 2D images of the skulls’ outline and 3D scans of their surface. The group also compared them to skulls from other other archeological sites in Japan, such as the Doigahama Yayoi people in Western Yamaguchi, and the Kyushu Island Jomon people, who were the hunter-gatherer predecessors to the Yayoi people.

‘Our results revealed distinct cranial morphology and significant statistical variability between the Hirota individuals with the Kyushu Island Jomon and Doigahama Yayoi samples,’ said Dr Seguchi. 

‘The presence of a flattened back of the skull characterised by changes in the occipital bone, along with depressions in parts of the skull that connects the bones together, specifically the sagittal and lambdoidal sutures, strongly suggested intentional cranial modification.’

The sagittal suture is the joint between the two parietal bones across the top of the skull – lamboidal sutures join the occipital bone to the parietal bones at the back.

‘Our findings significantly contribute to our understanding of the practice of intentional cranial modification in ancient societies,” said Dr Seguchi. 

Many refer to the practice as artificial cranial deformation, given the individuals affected may not have had control over whether or not they took part.

Why the Hirota people engaged in such extreme body modification is not known, but one reason could be to help preserve group identity.

‘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,’ said Dr Seguchi.

The study is published in the journal PLoS One.

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