Ecology and Evolution: Ecology and Evolution: Animal Peoples: News:

Skeletal fossil of Australopithecus sediba and invented by Lee Berger. The size of the brain is incomparable, but the brain of modern humans is not very large. Courtesy of Wikimedia Commons

If the ancient man enters an unfamiliar road or encounters bad weather while chasing a new game, he must make a decision based on his own experience and judgment to survive. The advice of the elderly would have been important, but the amount of information would have been less than today’s new climbers with a single cell phone armed with a portal and GPS. One study found that the capacity of the human brain began to decline rapidly 3,000 years ago because we relied on collective intelligence. It is the content that mankind has achieved by reducing the brain, the organ that stores energy outside and expends energy. Researchers in various fields, including anthropology, evolutionary biology, and neuroscience, including Professor Jeremy DeSilva at Dortmouth College in the United States, put forward this hypothesis in a study published in the latest issue of the scientific journal The Boundaries of Ecology and Evolution. I found the human brain to contract by expanding, ”he said.

Evolution of human brain capacity. The period of rapid expansion began 2.1 million years ago and contracted 50 times faster than the trend of increase that existed 3,000 years ago. The expanded map on the right represents the last 100,000 years. Courtesy of Jeremy DeSilva et al (2021) ‘Ecological and Evolutionary Frontiers’.

Researchers first studied changes in human skull capacity over the past 10 million years in 985 skulls from human ancestors to modern humans. It revealed three turning points in the expansion and contraction of the brain. In the six million years since our ancestors separated from our chimpanzees, our brains have quadrupled. The rate of brain expansion, which was initially slow, showed a steep increase 2.1 million years ago, and although it had subsided some 1.5 million years ago, it still increased rapidly. However, 3,000 years ago, the development of the brain turned into a sharp decline. James Traniello, a professor at the University of Boston who participated in the study, said, “Human brains are overgrown and their heads are too big. In the press release Said. Humans already had large brains, meaning that the brains of Australopithecus were 20% larger than those of modern chimpanzees, but the upright cause of the Homo species appeared, and the use of fire and stone tools led to the rapid evolution of a larger brain.

Image by a Neanderthal who lived 40,000 years before the Pleistocene. It is one of the most intelligent species among the direct ancestors of mankind. Dutch Museum, courtesy of Wikimedia Commons

However, at the end of the Pleistocene, as the ice age approached, the human brain suddenly began to contract. “It is amazing that the brains of modern humans are smaller than the brains of our Pleistocene ancestors,” said Professor DeSilva, the lead author. Meanwhile, various hypotheses have emerged in education that humans are ‘self-developing’ rather than brain-shrinking or that wild animals have lost their brains in raising them. Moreover, the period is as different as 35,000 to 10,000 years ago. In this study, the researchers rejected the current hypothesis, saying that reducing the size of the brain is five times greater than the size of the body, and that self-domestication took place 20,000 years before dogs were bred. In addition, with accurate brain size analysis, the period of the fall advanced to 3,000 years ago. The researchers found the cause of the rapid brain contraction in the social evolution of ants. Professor Traniello said, “It is difficult to understand why the brain grew or became smaller from the fossils of human bones.

Scissors ants cut leaves, collect them and feed on mold. If the population was large, the brains of the worker ants were found to be smaller. Courtesy of Adrian Fingston, Wikimedia Commons

Researchers have confirmed that the brain size of worker ants changes according to the group-level cognitive ability and labor differences of studies of weaver ants, cut ants and fire ants. The more knowledge is shared, the more the brain becomes smaller (more efficient) as a person specializes in a particular task in a social group. Professor Traniello said, “Human and ant communities are very different and have evolved socially in completely different ways. However, humans and ants are identical in key aspects of social life, such as production.”

Weaver ants can form large groups of more than 500,000. Mark Marathon, courtesy of Wikimedia Commons

Our brain is only 2% of our body weight, but it uses 20% of our body’s energy. Therefore, reducing the capacity of the brain was a powerful choice stress for our ancestors, as they had a high load on the brain to use energy. Researchers believe that the size of the brain can be reduced by releasing knowledge into human society and by reducing the amount of information stored by individuals. “Our hypothesis is that we can reduce the size of the brain by relying more and more on collective intelligence,” Tranello said. Documents cited: Boundaries of ecology and evolution, DOI: 10.3389 / fevo.2021.742639 Reporter Joe Hong-siop [email protected]