Human brain capacity is closely related to the level of intelligence. How big was the brain capacity of ancient humans? Scientists tell you the answer. Researchers from the Institute of Paleovertebrates and Paleoanthropology of the Chinese Academy of Sciences and other units restored the relatively complete skull of Xujiayao people in the late Middle Pleistocene for the first time, and successfully calculated the brain capacity of Xujiayao people. Relevant research results are published online in the international professional journal Journal of human evolution. "Combined with intracranial model and formula method, we calculate that the brain volume of Xujiayao people is about 1700ml. This is the 'big head man' with the largest brain volume in the Middle Pleistocene so far." On January 12, Wu Xiujie, a researcher at the Institute of ancient vertebrae of the Chinese Academy of Sciences, told the science and technology daily. Xujiayao human fossil was found in Xujiayao site (also known as houjiayao site) at the junction of Shanxi Province and Hebei Province from 1976 to 1979. The fossil is relatively broken, including 18 skull fragments and 3 free teeth. These fossils represent more than 10 individuals. "According to the associated mammal species, stratigraphic burial and various dating, the researchers judged that the Xujiayao people lived in the late Middle Pleistocene, about 200000 to 160000 years ago." Wu Xiujie introduced. Previous studies have shown that Xujiayao people are a very special group of ancient humans. Their physical characteristics show the mixed characteristics of East Asian Homo erectus, European Neanderthals and early modern humans in the late Pleistocene. Their evolutionary positions have been successively classified into early Homo sapiens, Neanderthals, late ancient humans, denisovans and unknown populations, The growth and development pattern of its teeth has entered the ranks of modern people. It is generally believed that the brain capacity of Pleistocene paleohumans increased with geological age. For example, the brain capacity of Australopithecus is 404-530 ml, that of Homo sapiens is 510-752 ml, that of Homo erectus is 600-1251 ml, that of ancient Homo sapiens in the Middle Pleistocene is 1100-1450 ml, and that of early modern humans and Neanderthals in the early Late Pleistocene increased to more than 1500 ml. However, "in recent years, the discovery of new fossils has changed people's traditional cognition." Liu Wu, a researcher at the Institute of ancient vertebrae of the Chinese Academy of Sciences, said that the Naledi people found in Africa about 300000 years ago in 2013 had a brain capacity of only 560ml; In 2003, the brain capacity of the Floris people discovered in Indonesia from 100000 to 50000 years ago was only 400 ml; In 2017, the skull capacity of Xuchang people reported from 125000 to 105000 years ago reached 1800 ml. "Although some scholars have put forward various hypotheses about the jumping changes of individual Pleistocene ancient human brain, such as the diversity of food, the change of environment and climate, the complexity of human behavior and so on, many hypotheses are not convincing." Wu Xiujie explained. Using CT technology and mirror image principle, the researchers restored the relatively complete skull of Xujiayao people for the first time, which provided important specimen materials for observing the overall morphological characteristics of Xujiayao people. Combined with intracranial model and formula method, the researchers calculated that the brain capacity of Xujiayao people was about 1700ml, which was close to the previously reported brain capacity of 1800 ml of Xuchang people, but nearly 60000 years earlier than that of Xuchang people. "There is no doubt that this is the ancient human with the largest brain capacity in the Middle Pleistocene, including the early Pleistocene." Wu Xiujie stressed. "Our study found that the skulls of Xujiayao people and Xuchang people are very similar in shape. They both have large heads and low skulls, and both have the unique inner ear labyrinth pattern of Neanderthals. They may be the same population. Considering that Xujiayao people are older than Xuchang people, it is possible that Xujiayao people are the direct ancestors of Xuchang people!" Wu Xiujie said that from 300000 to 100000 years ago, there may be a kind of "big head people" with special physical characteristics in China. In recent years, some paleoanthropologists around the world have put forward the hypothesis that the denisovans may exist in the fossil records of China, especially the Xuchang and Xujiayao people. "If this is true, the cranial capacity of the denisovans may also be large." Liu Wu said. (Xinhua News Agency)