Japanese Skulls Have Become Rounder and Wider-Jawed Over Past Century

Japanese people’s heads have become rounder over the past 100 years, with narrower cheekbones, wider upper jaws and slimmer, more prominent noses. People who died between 1900 and 1920 had longer skulls from front to back compared with more recent populations. Skulls have mostly lost the oval shape they once had at the turn of the 20th century.

Shiori Usui at the National Research Institute of Police Science in Chiba, Japan, and her colleagues performed CT scans on the skulls of 34 men and 22 women who died of natural causes between 1900 and 1920. The bodies of those individuals were donated to the Kyoto University Medical School for dissection and later became skeleton specimens in the museum.

The team collected scans from 29 men and 27 women who died between 2022 and 2024 whose bodies had undergone autopsy imaging.

Researchers used 161 landmarks on 3D skull images to measure shape. People have become more brachycephalic over the past century. Foreheads have got shorter, starting higher on the face, and have become slightly more dished while the mastoid process has become larger and more projecting.

Scientists often use measurements from 19th- and early 20th-century human remains as references for “modern” humans. People are generally taller and larger today than a century ago due to changes in health, diet and environment. Usui suspected those same factors might affect head shape.

The changes in skull shape seem too recent to result from genetic evolution. The skull changes probably result from better health and nutrition during childhood and eating softer foods that require less chewing.

The differences between male and female skulls are larger than they were 100 years ago. Male skulls have stronger brow ridges, larger mastoid areas and more projecting faces than female skulls. Sexual dimorphism in skulls has actually increased over the past century.

“This was a striking and unexpected result for us,” Usui said. “We expected to see more ‘neutral’ facial structures. ” A 2024 US study hinted at similar changes in men’s and women’s faces over time. A US study published in 2000 pointed to skulls becoming more oval than round in the past 100 years.

70235. Francesco Cappello at the University of Palermo, Italy, said the study underscores that even relatively recent human populations continue to change. “This raises important questions about the interplay between genetics and environment – especially in traits that have traditionally been considered relatively stable, like that of the biomorphology of the bones,” he said.

Kimberly Plomp at the University of the Philippines Diliman said the findings suggest scientists should consider updating standards for identifying human remains. “If modern human crania, and potentially other bones, have changed in morphology in such a short period of time, this could mean that the methods we use are no longer as accurate as hoped,” she said.

” @NewScientist reported that while changes outside Japan may vary, the overall trend is probably common across the globe as lifestyles modernise worldwide.