Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, revealed about the human brain and when the typical globular brain shape of modern humans evolved. Their analyses based on changes in endocranial size and shape in Homo sapiens fossils show that brain organization, and possibly brain function, evolved gradually within our species and unexpectedly reached modern conditions only recently. The study got published in Science Advances.

The evolutionary history of our own species can be traced back to fossils from Jebel Irhoud (Morocco) dated to about 300,000 years ago. Last year's analysis of these fossils by researchers from the Department of Human Evolution at the Max Planck Institute for Evolutionary Anthropology in Leipzig was highlighted as one of the top science stories of 2017 by a diverse range of print and online media.

Together with crania from Florisbad (South Africa, 260,000 years old), and Omo Kibish (Ethiopia) dated to 195,000 years ago, the Jebel Irhoud fossils document an early evolutionary phase of Homo sapiens on the African continent. Their face and teeth look modern; however, their elongated braincase appears more archaic as in older human species and in Neanderthals.

In contrast, it is a globular braincase, which characterizes the skull of present-day modern humans together with small and gracile faces. Two features of this process stand out: parietal and cerebellar bulging. The Homo sapiens fossils were found to have increasingly more modern endocranial shapes in accordance with their geological age.

Only fossils younger than 35,000 years show the same globular shape as present-day humans, suggesting that modern brain organization evolved some time between 100,000 and 35,000 years ago. A modern human brain shape was not established at the origin of our species together with other key features of craniodental morphology.

Evolutionary changes in early brain development

In present-day humans, the characteristic globular shape of the braincase develops within a few months around the time of birth. Philipp Gunz explains, "The evolution of endocranial shape within Homo sapiens suggests evolutionary changes of early brain development.

A critical period for neural wiring and cognitive development. The researchers therefore argue that evolutionary changes to early brain development were key to the evolution of human cognition.

Jean-Jacques Hublin, says: "The gradual evolution of modern human brain shape seems to parallel the gradual emergence of behavioral modernity as seen from the archeological record." The new findings agree with recent genetic studies that show changes in genes related to brain development in our lineage since the population split between Homo sapiens and Neanderthals.

They conclude that accumulating archeological and paleoanthropological evidence demonstrating that Homo sapiens is an evolving species with deep African roots and long-lasting gradual changes in behavioral modernity, brain organization, and potentially brain function.