The size of the human jaw and the shape of the teeth have evolved following the change in the human diet.. When our hominin ancestors switched to softer foods and developed technologies for preparing them, the effort to chew food was significantly reduced, the size of the jaws and teeth became much smaller.. The cost of energy required for chewing has also decreased, writes Science..
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Adam van Casteren, a biological anthropologist at the University of Manchester, and his colleagues did a pretty neat experiment.. Put on 21 test subjects, men and women helmets that look like bubbles. The device measured the amount of oxygen they consumed and the carbon dioxide they exhaled.. The scientists then gave the participants flavorless, odorless, and calorie-free chewing gum that they chewed for 15 minutes..
While chewing, the level of CO2 in the volunteers' breath increased, indicating that their bodies were working harder.. When chewing gum was soft, the volunteers' metabolism increased by an average of 10%.; a stiffer band requires 15% more energy than rest.
If ancient humans spent as much time chewing gum as gorillas and orangutans chewing roughage, researchers estimate they could have spent at least 2.5% of their energy budget chewing.. These experimental results came as a surprise..
According to the researchers, the experiment confirmed that a less coarse diet and saving calories that are sharpened by chewing could be an evolutionary advantage.. Indeed, human ancestors had more time for other activities..
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Calculating the energy cost of human chewing may also provide insight into the evolutionary strategies of other hominins.. For example, Australopithecus, a hominid that lived in Africa between 2 and 4 million years ago, had teeth four times the size of modern humans and massive jaw muscles..
Compared to australopithecines or primates living today, humans are an exception.. According to some estimates, we only spend 7 minutes per day chewing.. In contrast, mountain gorillas can spend up to 90% of their waking time chewing, on par with ruminants such as goats and cows..
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Well, the lack of need for powerful jaw muscles allowed the cranium and brain to grow, which became the main evolutionary advantage of man..