The modern human brain originated in Africa about 1.7 million years ago

Skulls of an early homo from Georgia with a monkey-like monkey (left) and from Indonesia with a human-like brain (right). Credit: M. Ponce de León and Ch. Zollikofer, UZH

The human brain as we know it today is relatively young. It developed approximately 1.7 million years ago when the culture of stone tools in Africa became increasingly complex. Soon after, new populations of Homo spread to Southeast Asia, researchers from the University of Zurich showed using computed tomography analysis of fossilized skulls.

Modern humans are fundamentally different from our closest living relatives, the great apes: We live on earth, walk on two legs, and have a much larger brain. The first populations 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 today’s people. These earliest homo populations in Africa had primitive monkey-like brains – just like their extinct ancestors, the australopithecines. So when and where did the typical human brain evolve?

CT comparison of the skull reveals modern brain structures

An international team led by Christoph Zollikofer and Marcia Ponce de León from the Department of Anthropology at the University of Zurich (UZH) has now managed to answer these questions. “Our analyzes suggest that modern human brain structures appeared only 1.5 to 1.7 million years ago in African homo populations,” Zollikofer says. The researchers used computed tomography to examine the skulls of homo fossils that lived in Africa and Asia 1 to 2 million years ago. They then compared the fossil data with the reference data of great apes and humans.

In addition to size, the human brain differs from the brains of great apes, especially in the position and organization of individual brain regions. “Characteristics typical of humans are primarily those regions in the frontal lobe that are responsible for planning and executing complex patterns of thought and action, and ultimately for language,” notes first author Marcia Ponce de León. Because these areas are significantly larger in the human brain, adjacent areas of the brain have shifted backward.

The modern human brain originated in Africa about 1.7 million years ago

The skull of early Homo from Dmanisi in the state of Georgia, which shows the internal structure of the brain, also concluded about the morphology of the brain. This was discovered by computed tomography and virtual reconstruction. Credit: M. Ponce de León and Ch. Zollikofer, UZH

The typical human brain spread rapidly from Africa to Asia

The first homo populations outside Africa – in Dmanisi in present-day Georgia – had brains as primitive as their African cousins. It follows that the brains of early humans did not become particularly large or particularly modern about 1.7 million years ago. However, these early humans were quite capable of making a number of tools, adapting to the new environmental conditions of Eurasia, developing animal feed sources, and caring for members of the group who needed help.

The modern human brain originated in Africa about 1.7 million years ago

Early homo skulls from Dmanisi, Georgia (samples D2280, D2282, D2700, D3444, and D4500) with internal brain structures detected by computed tomography and virtual reconstruction. Credit: M. Ponce de León and Ch. Zollikofer, University of Zurich

During this period, cultures in Africa became more complex and diverse, as evidenced by the discovery of different types of stone tools. Researchers believe that biological and cultural evolution are probably interdependent. “Probably even the earliest forms of human language developed during that period,” says anthropologist Ponce de León. Fossils found in Java prove that the new populations were extremely successful: shortly after their first appearance in Africa, they had already spread to Southeast Asia.

The modern human brain originated in Africa about 1.7 million years ago

Dmanisi cranium D4500, mounted for ID17 beam synchrotron tomography at the European Synchrotron Radiation Plant, Grenoble, France. Credit: Paul Tafforeau, ESRF

Brain prints in fossil skulls reveal the evolution of humans

Previous theories did not support them much due to the lack of reliable data. “The problem is that the brain of our ancestors was not preserved as a fossil. Their brain structures can only be determined based on the prints left by the folds and furrows on the inner surfaces of the fossil skulls,” says study leader Zollikofer. Because these prints vary considerably from individual to individual, it has not been possible to determine clearly so far whether a particular homo fossil had a brain more similar to an ape or more to a human. Using computed tomographic analysis of a series of fossil skulls, the researchers were able to reduce that gap for the first time.


Evolutionary research suggests prehistoric human fossils lurking “in sight” in Southeast Asia


More information:
MS Ponce de León el al., “The Primitive Brain of Early Homo,” Science (2021). science.sciencemag.org/cgi/doi… 1126 / science.aaz0032

A. Beaudet el al., “The Mysterious Origin of the Human Brain,” Science (2021). science.sciencemag.org/cgi/doi… 1126 / science.abi4661

Provided by the University of Zurich

Citation: The modern human brain originated in Africa about 1.7 million years ago (2021, April 8), retrieved April 8, 2021 from https://phys.org/news/2021-04-modern-human-brain- africa-million.html

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