As humans evolved, changes in diet changed our tooth enamel at the nanoscale
Primate tooth enamel has evolved at the crystalline molecule level over nearly 18 million years to adapt to dietary shifts, according to research published in Nature (DOI: 10.1038/s41586-026-10583-8). The study found that the addition of meat and agricultural products to human diets altered how individual nanocrystals in enamel orient to one another, changing the structure of the hardest tissue in vertebrates.
Enamel consists of tightly packed rods made of tiny hydroxyapatite crystals and interrods, which are the spaces between those rods. Pupa Gilbert, a biophysicist at the University of Wisconsin–Madison, identified that the misorientation of these individual crystals correlates directly with the hardness of tooth enamels.
How did diet change human tooth structure?
Researchers compared premolar teeth from 12 different species using fossil records. They found that crystal orientations—the angles between adjacent crystals—shifted as food hardness increased. Species consuming seeds showed the highest amount of misorientation, while fruit-eating primates and monkeys showed the least.
In humans, the study identified two primary structural shifts. The first occurred between 1.5 million and 2.0 million years ago, coinciding with the transition to meat eating. The second happened approximately 12,000 years ago when the rise of agriculture introduced stone-ground grains into the human diet.
Did You Know? In nonhuman primates, the level of crystal misorientation in enamel varies by diet, with seed-eaters possessing the highest levels and fruit-eaters possessing the lowest.
Why didn’t the Industrial Revolution affect enamel?
The research team found that a third major dietary shift during the Industrial Revolution did not result in nanolevel alterations to enamel structure. Mackie O’Hara, an anthropologist at Ball State University and coauthor of the paper, suggests this is likely because the Industrial Revolution is only about 200 years old.
O’Hara noted that evolution is not mandatory simply because it is possible. She explained that enamel has many different hierarchical levels of structure, meaning environmental conditions could affect any one of those levels rather than specifically the nanostructure.
Expert Insight: The lack of change during the Industrial Revolution underscores the distinction between rapid cultural shifts in diet and the slower pace of biological evolution. The stability of the nanostructure suggests that the “hierarchical levels” O’Hara mentioned provide a buffer, where biological adaptation may occur at scales other than the nanocrystal level.
What are the implications for materials science?
The findings regarding crystal misorientation may assist materials scientists in creating bioinspired materials. Nicholas Kotov, a materials engineer at the University of Michigan, stated the study helps researchers design complex multifunctional materials for various technologies.
According to Kotov, the research emphasizes the necessity of balancing order and disorder to meet multiple property requirements. Future applications could see the development of synthetic materials that mimic this biological balance to achieve specific hardness or durability levels.
Frequently Asked Questions
What is tooth enamel composed of?
Enamel is made of tightly packed rods containing tiny hydroxyapatite crystals, with spaces between them known as interrods.
When did the most significant changes in human enamel occur?
Two main changes occurred: one between 1.5 million and 2.0 million years ago during the shift to meat eating, and another about 12,000 years ago with the introduction of agricultural stone-ground grains.
Did recent dietary changes from the Industrial Revolution change tooth crystals?
No. Researchers found that the dietary shifts of the Industrial Revolution did not correspond with any nanolevel alterations in enamel structure.
How do you think our current processed diets might influence the future of human dental anatomy?