Dental practitioners (e.g., orthodontists) and anthropologists have different perspectives on tooth crowding in modern populations. Can you understand why this is the case? For a hint, think of the subjects dentists deal with as opposed to the subjects anthropologists deal with. Dentists and anthropologists agree that crooked or crowded teeth are a function of jaw size and tooth size incompatibility. When an individual has large teeth and small jaws measured by arch width and length, the inevitable consequence is tooth crowding. Given the long-term trend in jaw size reduction, why don’t all individuals have crowded teeth? 

Because of their critical function in chewing food, tooth development is under strong genetic control. For that reason, changes in size and morphology occur over long periods of time. Research on fossil hominins and recent human populations show there has been a gradual change in tooth size over the past 100,000 years. Not all populations have been equally affected though. Change is less pronounced in populations that have maintained a traditional hunting/gathering lifestyle until recent times. It is more pronounced in populations that switched economies from hunting/gathering to a dependence on domesticated plants and animals. This subsistence change occurred at different times in different places, e.g., 12,000 years ago in the Middle East to 4,000 years ago in West Africa. The variation in tooth size among modern human populations is one reason there is geographic variation in the frequency of tooth crowding. 

For additional information, watch the TED-Ed video How did teeth evolve?, as well as additional videos on the crowding caused by wisdom teeth. 

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