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human evolution. Where did the human brain come from? – to know

human evolution.  Where did the human brain come from?  - to know

For years, scientists have been puzzled as to why the brain of Homo erectus has evolved so dramatically. Until now, they were convinced that this is due to the fact that our ancestors introduced meat into their diet, which is a rich source of calories, protein and a huge variety of valuable nutrients. Andrew Barr, an anthropologist at George Washington University, believes that the reason the brain grew was not in meat, because you had eaten it before, but that it was due to several different factors. The scientist described the details of his theory in the prestigious journal “Proceedings of the National Academy of Sciences”.

carnivores

“Flesh made us human,” Henry T Boone, an anthropologist at the University of Wisconsin-Madison, said years ago. Many of his colleagues agreed with this claim because archaeologists conducting research in East Africa had been providing evidence since the 1980s that meat was a staple in the diet of Homo erectus or its close ancestors. They found mounds of fossilized animal bones with scars and splintered flesh. It has also been observed that many great apes eat meat, and chimpanzees use simple tools for hunting.

Because the animals eat meat, the same food they eat cannot have contributed to rapid brain development as Homo erectus, said Richard Wrangham, professor of biological anthropology at Harvard and author of the popular book The Fight for Fire. How cooking made man. In his opinion, only heat treatment of meat changed the size of the human brain. In his book, Wrangham recalls that our ancestors hunted animals 2.5 million years ago, but their brains did not begin to develop until hundreds of thousands of years later.

Heat treatment deprives the meat of many parasites, and the meat itself becomes more digestible and more filling. It also provides more calories. “You can get about 50 percent of the total. More nutrients from raw meat,” says Robin Dunbar in “The Man.” Biography”. Meat contains not only a lot of calories, but also valuable nutrients – from proteins and fats to zinc, sodium, iron, calcium, vitamins A, K and group B. More valuable meals.

Read also: Meat is worse on Earth than cars and smoking factories

Free time

“Cooked food is easier to digest than raw food, which means we gain weight faster. And because digestion is an energy-intensive process – to get calories from food we also need to burn calories, and the faster we do that, the more energy we’ll give our body.” Wrangham’s experiments show that mice fed boiled meat gain more weight than their raw-fed relatives, writes Marta Zarasca in Meatholics. 2.5 Million Years of Homo Predator Mania.”

Robin Dunbar calculated that if our ancestor who lived 1.8 million years ago had not changed its diet, it would have had to spend more than 60 percent. It’s time to find food that meets your brain’s needs. This means that baking saved a lot of time. Observations of chimpanzees, the closest animals in the Tanzanian Gombe forest, show that these animals spend an average of six hours a day collecting and chewing plants. When plants are scarce in the dry season, chimpanzees go hunting together. Then the time spent getting food and eating it is, on average, halved. Modern man spends less than an hour a day on meals.

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Wrangham believes that our ancestors got four or five hours of free time by eating cooked foods that were softer than raw foods. They can spend it on mastering hunting techniques, making tools, or even decorating them. So they developed creativity, intelligence and social skills. After all, the hunt had to be organized, and the prey had to be shared. Therefore, our ancestors needed a greater mind than ever to understand the whole complexity of social life at that time, based on cooperation and friendship, but also on competition, dishonesty and deception.

Wrangham and his predecessors’ theory about the effects of meat on our brain was correct at first. Diet change also left its mark on the appearance of our ancestors’ faces. Hard, stringy foods that need to be bitten hard and chewed for a long time have been replaced by soft foods. As a result, the teeth and muscles of the upper jaw and lower jaw were significantly reduced. The digestive system has also changed – the intestinal space has decreased. As a result, the entire digestive system has become more like our own.

However, this theory had a significant drawback – no traces of fire were found in the places where Homo erectus lived. Previous research has shown that 790,000 people have learned to use fire. Years ago, that is, long after their brain had significantly enlarged. Wrangham argued that the lack of evidence is not evidence in conflict with the theory. In his opinion, sooner or later archaeologists will find discoveries that prove that Homo erectus uses fire. He wrote in his book that our ancestors used fire about two million years ago.

chopping, slicing, crushing

Thirteen years have passed since Wrangham published his theory in 2009. However, no one has found any foci dating from 2-1.8 million years ago, the period when one of our ancestors experienced remarkable brain growth. And you can’t complain about the lack of searches. A crowd of ancient anthropologists went to the famous and well-preserved archaeological sites, such as Olduvai Gorge. There traces of the existence and remains of our ancestors dating back 2.6-1.7 million years were discovered. Animal bones from that period and stone tools were also found. They found amazing evidence that early humans ate animals. Thus, they confirmed the view that our ancestors fell in love with meat about two million years ago. However, that theory begins to fall apart when data from several archaeological sites in East Africa are analyzed to verify the “meat made us human” hypothesis, as we did, said Dr. W. Andrew Barr of The George Washington University.

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Dr. Barr and his team collected data from nine major research areas in East Africa, including 59 sites dating from 2.6 million to 1.2 million years ago. They analyzed the places where animal bones were preserved, examined the bones and counted the cut marks made from stone tools. They found that with the advent of Homo erectus, the number of archaeological and anthropological sites increased, and thus the number of tested specimens increased. However, there is no indication that the way of life of our ancestors has changed radically. There is no evidence of more meat in the diet of Homo erectus than on the menu of our early ancestors.

– For more than 20 years, I have been digging, examining and wounding bones, but this discovery came as a great surprise to me. This is changing our view of our meat-eating ancestors, said Brianna Poppiner, a paleontologist with the Human Origins Program at the Smithsonian National Museum of Natural History.

So, since meat was not a common dish for our ancestors as scientists believe until now, what prompted Homo erectus to change anatomical features? Perhaps there is a taming of fire permission, as Richard Wrangham claims. Perhaps not only hunted animals, but also various tubers were roasted? But if so, why are there no traces of ash at sites from Homo erectus?

The solution to this puzzle was proposed eight years ago by Catherine Zink and Daniel Lieberman, evolutionary anthropologists at Harvard University. They published in the pages of nature the results of their work, where they said that before man began to use fire – to light it or drive embers away from natural fires and bake meat on them – he learned to cut and crush it. For years, archaeologists have found many traces of wounds on bones at different sites from the times of our ancestors. It is common knowledge that small pieces of meat do not have to be chewed as hard as large pieces. Big teeth and massive jaws are no longer needed. Such preliminary processing of meat and perhaps also plant parts, which after many years did not survive in fossil material, meant that Homo erectus did not waste much time eating and could take on something more creative.

Grandmothers prevail

But this theory also has a significant drawback – scientists find bones with traces of wounds at sites that are 3.5 million years old. This means that early humans scraped up the bones and crushed them with stone tools. Our ancient ancestors extracted from them bone marrow, which is very nutritious and rich in proteins, fats and vitamins. And maybe they can cut the meat into pieces. So why were their jaws and mandibles as huge as those of non-human primates?

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Scientists have not yet answered this question. Some people think that the fine structure of the face is caused by some random mutation. Others believe that the solution to this mystery lies in social change and related dietary modifications. An interesting theory was proposed ten years ago by Prof. Kristen Hawkes, an anthropologist at the University of Utah. In her view, the driving force in the evolution of our species has been grandmothers, specifically menopausal women. Not only did the grandmothers help take care of their grandson when the mother had already weaned them from her breast, but they also got food for the grandson.

The grandmothers hypothesis led Prof. Hawkes sights of the Hadza people of Tanzania who are hunter-gatherers and still live the same way their ancestors did thousands of years ago. The scientist pointed out that the elderly women in this society are much more skilled than the younger ones in finding and digging edible tubers. Therefore, I decided that the food that the grandmothers get increases the chances of survival of the grandchildren, but that it also represents a valuable variety of the diet. The more diverse and nutrient-rich our diet is, the healthier we will be.

By changing the menu, Dr. Peter Ungar, an anthropologist at the University of Arkansas, sees the evolutionary success of our ancestors and ourselves. The scientist, who in his research focuses on the importance of diet in human evolution, argues in the pages of science that the history of human evolution is too complex to explain in a simple way what made us human. He believes that there is no single theory that answers the question of why we owe our brains such leaps and bounds. “You can’t say that fire or stone tools made us human,” Dr. Angar says. Both of these things, and perhaps more, mean that our ancestors had better and better access to a wide variety of food products. Thanks to this, not only the brain of Homo erectus developed, but the whole organism better and better adapted to changing environmental conditions. So that he could leave Africa, capture almost all of Western Europe and reach the eastern edge of Asia.

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