What makes humans different from chimpanzees?
The human brain weighs 1. 4 kilograms, about 3. 5 times the weight of chimpanzees, and the number of nerve cells in the cerebral cortex is 14 billion, 1. 8 times that of chimpanzees.
Exactly what kind of creature humans are, this is one of the great mysteries that scientists very much want to find out. In addition to investigating the behaviour of apes such as chimpanzees, which are closest to humans, there was a new way of comparing genes in the 2000s. In this field, Japan has contributed a lot, and recently investigated the role of genes in the brain, closer to the human secret.
According to the Nikkei Shimbun on December 20, about 98.8 percent of all genetic information in humans and chimpanzees is the same, and only 1.2 percent is different. However, the social life forms and behavior patterns of the two are quite different. Why is that?
Research groups from the Life Genesis Research Center, Kyoto University, Niigata University, and the Chinese Academy of Sciences, natural science institutions in Japan, believe that the brain is the key organ that determines the vast differences between humans and chimpanzees. The human brain weighs 1. 4 kilograms, about 3. 5 times the weight of chimpanzees, and the number of nerve cells in the cerebral cortex is 14 billion, 1. 8 times that of chimpanzees.
“I’m not sure to what extent we can tell the difference between humans and chimpanzees,” recalled Kangguang Xiang, a special professor at the Center for the creation of Life, who published his work in August 2018. I was surprised at the unexpected results. ”
Brain research is difficult and almost impossible to begin with. After a very rigorous procedure, the team collected brain tissue from six humans, six chimps, two gorillas and one gibbon immediately after natural death, and studied the type and amount of RNA contained in it. Based on this information, it can be inferred which genes are active in which areas of the brain.
The analysis showed a total of 1851 genes for specific activity in the human brain, compared with 240 in chimpanzees, the former is about 7.7 times as large as the latter. From the view of shared function, the active working of human genes is particularly prominent in the premotor area, which determines the body movement, and the “hippocampus”, which is related to memory formation and spatial learning. The results “may have explored significant changes in the formation of human traits,” Mr. Heung explained.
Humans and chimpanzees evolved separately from a common ancestor about 5 million-7 million years ago. Scientists have been doing research to discover the differences and “what humans are” by investigating the behaviour and abilities of fellow primates. These studies have yielded many results.
Man is probably the most imaginative of all animals and has a high level of speech. For example, if we see the word “red”, we will think of red. Parents use language to educate and improve their children’s abilities.
Chimpanzees, on the other hand, can be said to be egocentric, taking into account only the immediate situation. Even if the child sees the fruit on the tree for the first time, the parents can only eat it themselves to demonstrate, and they can’t tell the child that it can be taken off and eaten. Chimpanzees are also different from humans in many other ways, including not being able to praise, help, or identify with others as humans do.
The method of assembling groups is also different between the two. Human beings have created the family, the smallest unit of the collective, family members together to form a community. Chimpanzees have no family, only groups. The males in the group breed freely with unrelated females. If the baby is a male, it stays in the group, and if it is a female, it leaves the group.
Chimpanzees also have superior abilities to humans. One example is instant cognition and memory. Tetsuro Matsuzawa, a special professor at Kyoto University, said chimpanzees showed the ability to answer more quickly and accurately than humans in experiments that briefly displayed numbers on television and then sequentially pointed out smaller numbers.
Japanese researchers have been making contributions to the accumulation of comparative studies such as behavior. Matsuzawa, who has studied chimpanzees for about 40 years, said, “I think the way humans and chimpanzees use intelligence, the structure of the brain is different.”
On the basis of comparative study, there are new research methods using molecular biology. At a time when the international collaborative interpretation of the human genome will be completed in 2003, the Japanese Institute of Physiochemistry published the results of a comparison of the human and chimpanzee genomes in 2002. And this study has further achieved new results by analyzing genes in the brain.
It is not easy to study the relationship between genes and the behavior and ability of organisms. Experiments that manipulate genes to determine how they relate to behavior are difficult, and studies of humans and chimpanzees are even more difficult. “if you just look at genetic differences, you may not be able to fully display human traits,” Matsuzawa said. There seems to be a need to strengthen the techniques used so far to closely investigate chimpanzee behaviour and to compare it with other primates.