The human brain as we know it today is relatively young. Scientists have found that it originated about 1.7 million years ago.
The modern human brain was formed when the culture of stone tools in Africa became more and more complex. After a short time, new populations of Homo spread to Southeast Asia. Such conclusions were made by researchers from the University of Zurich, using computed tomography and analysis of fossilized skulls.
Modern people are fundamentally different from their closest living relatives, the great apes: we live on earth, we walk on two legs, and our brain is much larger. The first population of the genus Homo appeared in Africa about 2.5 million years ago. They were already walking upright, but their brains were about half the size of modern humans. These earliest populations possessed primitive ape-like brains, like their extinct ancestors, the Australopithecines. So when and where did the typical human brain evolve?
An international team of scientists led by Christoph Zollikofer and Marcia Ponce de Leon from the Department of Anthropology at the University of Zurich (UZH) was able to answer these questions. “Our analysis shows that the modern structures of the human brain emerged only 1.5-1.7 million years ago in populations of African Homo,” says Zollikofer. The researchers used computed tomography to study the skulls of Homo fossils that lived in Africa and Asia 1–2 million years ago. They then compared the fossil data with reference data for great apes and humans.
In addition to size, the human brain differs from great apes, in particular, the location and organization of its individual areas. “Typical human features are primarily those areas of the frontal lobe that are responsible for planning and executing complex patterns of thought and action, and ultimately language,” notes the first author of the work, Marcia Ponce de Leon. Since these areas are much larger in the human brain, its adjacent areas are shifted further back.
The first populations of Homo outside Africa – in Dmanisi in what is now Georgia – had the same primitive brains as their African cousins. It follows that the brains of ancient people did not become particularly large or especially modern about 1.7 million years ago. However, these early humans were quite capable of making numerous tools, adapting to the new environment of Eurasia, developing sources of animal feed, and caring for group members in need of help.
During this period, African cultures became more complex and diverse, as evidenced by the discovery of various types of stone tools. Researchers believe that biological and cultural evolution are likely interdependent. “It is likely that the earliest forms of human language also developed during this period,” says anthropologist Ponce de Leon. Fossils found in Java indicate that the new populations were extremely successful: soon after their first appearance in Africa, they had already spread to Southeast Asia.
Previous theories have not been supported by a lack of reliable data. “The problem is that the brains of our ancestors were not preserved as fossils. Its structures can only be identified by the imprints left by folds and grooves on the inner surface of the fossil skulls, ”concludes the head of the study. Because these prints vary widely from person to person, it has not been possible until now to determine unambiguously whether a particular fossil of Homo has a more ape-like or human-like brain. Using computed tomography analysis of many skull fossils, researchers have closed this gap for the first time.