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Homo erectus : The early man was not a vegetarian

Homo erectus is known as one of the first early humans with a considerable brain size - too big to supply the mass of nutrient-hungry nerve cells with plant food alone. In any case, it would have required a pronounced set of teeth. Homo erectus, who lived about two million years ago, had a much more delicate set of teeth with much smaller teeth than its evolutionary predecessor. The masticatory muscles were also weaker, he could bite less forcefully and the intestine was much shorter. So far, anthropologists have had three possible explanations for the contradiction between poorly performing teeth and a greater need for food. Either the early humans ate meat, cooked their food or worked it with their stone tools before eating.

According to a theory by the anthropologist Richard Wrangham of Harvard University in Cambridge, cooking is said to have enabled early humans to get more energy from the same amount of food. This would have allowed more people with large brains, reduced dentition and bowel length to survive and reproduce. However, there is no evidence that humans were grill masters two million years ago or earlier. The oldest human hearths found so far are only 500,000 years old. Earlier traces of prehistoric kitchens are not clearly of human origin.

Subjects had to chew tough goat meat

Wrangham's colleague at Harvard University, Daniel Lieberman of the Department of Human Evolutionary Biology, is known to be fond of teasing the kitchen theory of human evolution. Now, together with Katherine Zink, he has carried out some experiments to determine whether Homo erectus could be full enough without cooking. The researchers measured the chewing performance of a total of 34 test subjects who were fed goat meat on the one hand and nutritious tubers such as yams or carrots on the other, which were most likely an important part of the diet of early humans. “Goat is relatively tough and therefore more similar to the meat of wild animals than that of farm animals,” write Zink and Lieberman in the journal “Nature”.

They found that when a third of their diet consists of meat, people chew about two million times (13 percent) less and have 15 percent less chewing force. "Compared to unprocessed roots, around 39 percent less chewed meat and 46 percent less chewing power is required for a kilocalorie of meat," the researchers write. However, it was almost impossible for the test subjects to chew the raw meat. Even after biting 40 times, it was still just a single lump in the mouth.

Later stone age meat tenderizers were allowed to be used

Early humans could at least have pounded the meat soft or cut it with stone tools. It has been proven that they were used 3.3 million years ago. So when the test subjects in the Harvard experiment cut the meat into strips with simulated stone tools, they had to chew an additional five percent less and chew another 12 percent less. Lieberman and Zink also had their Stone Age actors beat the goat meat 50 times with the Stone Age meat beaters. As a result, however, it was not measurably easier to chew, so it got stuck in front of the throat as a barely swallowable lump.

In the case of the roots, on the other hand, pounding with the Stone Age bobbins reduced the necessary chewing performance by 4.5 percent, but not the chopping.

In a further series of tests, the long-suffering test subjects were at least allowed to eat stone-age grilled meat and roots in order to test to what extent cooking could have made it easier to eat. Roasted root vegetables therefore had to be chewed 14 percent less often than raw vegetables. Since tuber vegetables tend to be hard food, cooking them would significantly reduce the chewing effort, so that teeth that are not as large are necessary, the researchers write. They estimate that around 14 percent less chewing surface is required - which is pretty much the difference in size between the teeth of Homo erectus and Homo sapiens. Grilled meat initially requires more chewing force. However, the lump of meat melts in the mouth and the stomach and intestines get better access to the nutrients.

Stone Age food pyramid: one third meat

Homo erectus, however, didn't need a fire to make ends meet, argue Lieberman and Zink. Despite his small teeth, he was able to take care of his large brain without cooking by pounding tubers and enriching a third of his food with chopped pieces of meat. That saved him 2.5 million chewing times a year and a quarter less energy.

Ultimately, then, the use of stone tools to chop meat and pound roots made it possible for early man's body to change.

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