Dairy diet changed human skull shape

The cultural shift from hunter-gatherer to farmer has had an impact on the shape of the human skull, according to researchers at The University of California.

Around 10,000 years ago, hunter-gatherers began to rely on diets from domesticated plants and animals and it is around this time that archaeologists noted the skulls began to shrink. However, while previous studies have established a link between skull shape and agriculture in the past, the global extent of these changes has been difficult to understand.

University of Calgary postdoctoral researcher and former UC Davis student David Katz, Professor Tim Weaver and statistician Mark Grote studied 559 crania and 534 lower jaws from more than two dozen pre-industrial populations worldwide. They analysed the influence that an individual’s diet had on the shape, form and size of the human skull during the transition to agriculture.

The study, published in the Proceedings of the National Academy of Sciences, found that groups that consumed cereals and dairy exhibited minor changes in their skull shape. The temporalis, one of the major chewing muscles, reduced in size and changed position as humans turned towards farming. Consequently, the upper jaw became shorter and the lower jaw smaller.

“The effect of farming is mostly visible in the areas of the skull that generate or experience stress during chewing,” stated Katz. “The simplest explanation is that these stresses were reduced because farming diets were generally softer.”

This was due to the fact that humans who relied on hunting and foraging for their food sources put more effort into chewing than farmers who consumed a softer diet that required less strenuous chewing.

Katz created a wire frame model of the human skull and jaw to indicate the differences in skull shape between foragers and farmers.

“The main differences between forager and farmer skulls are where we would expect to find them, and change in ways we might expect them to, if chewing demands decreased in farming groups,” said Katz.

Although dairy is associated with contributing to stronger and healthier bones in modern society, Katz suggested that populations consuming soft dairy products such as cheese had the largest changes in skull morphology.

However, other factors such as sex and location were bigger drivers of the evolution of human skull shape.