Anthropologists have discovered that the brain of our anthropoid ancestors began to transform into a “human brain ” much later than previously thought: only about 1.7 million years ago.
The human brain is much larger than that of its closest humanoid relatives and has a markedly different structure of the cortex. Its tissues are not fossilized or preserved. Therefore, the brain of long-extinct human ancestors has to be evaluated by the endocast – the relief of the inner side of the skull, which reflects the grooves, convolutions, and even large vessels of the brain.
Some studies show that significant changes in the structure of the organ began as early as in Australopithecus, about 2.5-2.7 million years ago. However, the authors of the new article, published in the journal Science, came to a later period – 1.7 million years, that is, after the first migration of Homo from Africa.
The traditional theory of human evolution might change
Using the latest technology, the scientist scanned replicas of the lower part of the meninges of four men and one woman – representatives of Homo erectus, who were found in the 1990s in Georgia (the so-called Dmanisi hominids; it is believed that these are the first people who left Africa between 1.85 and 1.77 million years ago).
Then, in simple terms, she compared the inner surfaces of their skulls to modern humans. The coronary suture and the precentral sulcus attracted the particular attention of the researcher. In most modern people, they are displaced to give more space to the frontal lobes (including the one that actively participates in speech).
The structure of those brains rather resembled modern apes and australopithecines. Since this area is crucial for speech and the creation of complex instruments, it can be said that the early representatives of this genus did not have such abilities.
The researchers then applied the same techniques to the endocasts of much more ancient Homo fossils. Detailed 3D models of the inner surface of the skulls were obtained from the ancient inhabitants of Africa, as well as Western (Dmanisi) and Southeast ( Homo erectus ) Asia. In total, the researchers examined more than 30 remains from 70 thousand to two million years old.
The attention of scientists was immediately attracted by the place of convergence of the coronal suture and the precentral sulcus. In humans, they intersect closer to the front of the brain, and in humans, this point is shifted back due to the growth of the cortex of the frontal lobes.
It turned out that the Dmanisi, who lived about 1.8 million years ago, still retained the primitive arrangement of these areas. This, according to the authors, testifies to the primitiveness of their brains.
Evidence of a transition to a more modern structure of the frontal lobes was found in the inhabitants of Africa only after 1.7 million years ago, when, perhaps, they acquired the ability to speak and complex tool activity.
It turns out that this process began even later than the first migration of representatives of our genus ( Homo erectus ) from Africa, which is dated to about 2.1 million years ago.
At the same time, already one and a half million years ago, the inhabitants of Indonesia had a completely modern brain. This is evidenced in the remains that were found in Java, at the Sangiran site.
However, some researchers are skeptical about the interpretation of the data obtained. In their opinion, changes in physiology do not guarantee simultaneous intellectual changes. But now scientists understand in which direction to work next. Studying and comparing hundreds of other samples will help to say for sure if there really is such a pattern.
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• León, M., Bienvenu, T., Marom, A., Engel, S., Tafforeau, P., Warren, J., . . . Zollikofer, C. (2021, April 09). The primitive brain of early homo.
• Lucie Aubourg, A. (n.d.). Early humans walked upright while still having surprisingly simple brains.
• Science X Staff. (2021, April 08). Modern human brain originated in Africa around 1.7 million years ago.
• University of Zurich / ScienceDaily. (2021, April 08). Modern human brain originated in Africa around 1.7 million years ago.