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Changes in social systems such as information sharing and the division of labor do not require energy consumption and a large brain.

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

If the old man sets out on an unknown road or encounters bad weather while pursuing a new game, he must make a decision based on his own experience and judgment in order to survive. Advice from the elderly would have been important, but the amount of information would have been less than that of today’s new climbers with just one 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. This is the content that humanity has achieved by shrinking the brain, the organ that stores energy on the outside and expends energy. Researchers in various fields including anthropology, evolutionary biology and neuroscience, including Professor Jeremy DeSilva of Dortmouth College in the United States, have advanced this hypothesis in a study published in the latest issue of the scientific journal The Boundaries of Ecology and Evolution. I found that the human brain contracts as it expands, ”he said.

Evolution of the capacity of the human brain. The period of rapid expansion began 2.1 million years ago and contracted 50 times faster than the increasing trend that existed 3,000 years ago. The enlarged map on the right represents the last 100,000 years. Courtesy of Jeremy DeSilva et al (2021) “Ecological and Scalable Borders”.

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

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

Image of a Neanderthal who lived 40,000 years before the Pleistocene. It is one of the most intelligent species among the direct ancestors of humanity. 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 that of our Pleistocene ancestors,” said Professor DeSilva, the lead author. During this time, various hypotheses have emerged in education that humans ‘grow on their own’ rather than shrinking their brains or that wild animals have lost their brains while raising them. Moreover, the period is as different as it was 35,000 to 10,000 years ago. In this study, the researchers rejected the current hypothesis, claiming that the reduction in brain size is five times greater than body size and that self-domestication took place 20,000 years before the dogs were bred. . In addition, thanks to an accurate analysis of the size of the brain, the period of the fall has passed to 3,000 years ago. Researchers have found the cause of the brain’s rapid 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.

Scissor ants cut leaves, scoop them up, and feed on mold.  If the population was large, the brain of worker ants would turn out to be smaller.  Courtesy of Adrian Fingston, Wikimedia Commons

Scissor ants cut leaves, scoop them up, and feed on mold. If the population was large, the brain of worker ants would turn out to be smaller. Courtesy of Adrian Fingston, Wikimedia Commons

The researchers confirmed that the brain size of worker ants changes based on cognitive ability at the group level and differences in work from studies of weaver ants, cut ants, and fire ants. The more knowledge is shared, the smaller (more efficient) the brain becomes 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 the same in key aspects of social life, such as production. “

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

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

Our brain makes up 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 stress choice for our ancestors because they had a heavy 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 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,” said Tranello. Cited documents: Limits of ecology and evolution, DOI: 10.3389 / fevo.2021.742639 Reporter Joe Hong-siop [email protected]


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