Human activity causes severe dental defects in wild Japanese macaques

CENIEH leads a study on plane-form enamel hypoplasia (PFEH), a dental disease experienced by these primates living on Yakushima Island, due to deforestation or intensive agriculture in the region. 


The Dental Anthropology Group of the Centro Nacional de Investigación sobre la Evolución Humana (CENIEH), leads a paper published in the International Journal of Zoology on the prevalence and causes of plane-form enamel hypoplasia (PFEH), a dental condition experienced by wild Japanese macaques (Macaca fuscata) from Yakushima Island, due to the impact of human activities in the region. 

Researchers found that a striking 48% of macaques living on this island in southwestern Japan show this condition, which causes large areas of the dental crown to lack enamel.

In affected macaques, the mineral content of remaining enamel was normal, ruling out factors such as deficient or excessive mineralization, genetic diseases (amelogenesis imperfecta) or localized enamel trauma as the triggering causes of these severe dental defects.

Anthropogenic impact

In fact, the study highlights anthropogenic impact, i.e. human activity, in particular deforestation, agriculture and persecution of Yakushima macaques as a cause of their condition, since these activities are likely to have led to stress, malnutrition and changes in their diet.

The study also demonstrates the complex interplay between environmental factors and primate health, providing crucial insights for conservation efforts and understanding the impact of human activities on wildlife.

 “We hope this study opens new avenues for further research on the health and physiological stress of macaques and other primates, using enamel hypoplasia as an indicator. We believe it is critical to study the interrelation of nutrition, population health, and anthropogenic impact on wildlife," says Ian Towle, leading author of this study.

This research was supported by the European Research Council within the European Union’s Horizon Europe (ERC-2021-ADG, Tied2Teeth, project no. 101054659), and Sir Thomas Kay Sidey Postdoctoral Fellowship from the Faculty of Dentistry, University of Otago, and it represents a collaborative effort involving the Primate Research Institute, Kyoto University.