Nav: Home

Modern human brain organization emerged only recently

January 25, 2018

Researchers from the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, reveal how 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 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 Neandertals. In contrast, it is a globular braincase, which characterizes the skull of present-day modern humans together with small and gracile faces.

In a new paper published in Science Advances, members of the same research team now reveal additional surprising findings about brain evolution in Homo sapiens. The paleoanthropologists Simon Neubauer, Jean-Jacques Hublin and Philipp Gunz used micro computed tomography scans to create virtual imprints of the internal bony braincase, so called endocasts that approximate brain size and shape. They used state-of-art statistics to analyze endocasts of various fossils and present-day humans.

Evolution of the parietal lobe and the cerebellum

Neubauer and colleagues document a gradual change within Homo sapiens, from an elongated endocranial shape towards a more globular one. Two features of this process stand out: parietal and cerebellar bulging. Parietal brain areas are involved in orientation, attention, perception of stimuli, sensorimotor transformations underlying planning, visuospatial integration, imagery, self-awareness, working and long-term memory, numerical processing, and tool use. The cerebellum is not only associated with motor-related functions like the coordination of movements and balance, but also with spatial processing, working memory, language, social cognition, and affective processing.

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. Importantly, these shape changes evolved independently of brain size -- with endocranial volumes of around 1,400 milliliters, even the oldest Homo sapiens fossils from Jebel Irhoud fell within present-day variation of brain size. "The brain is arguably the most important organ for the abilities that make us human," says Neubauer. But modern human brain shape was not established at the origin of our species together with other key features of craniodental morphology. Neubauer adds: "We already knew that brain shape must have evolved within our own species, but we were surprised to discover just how recent these changes to brain organization were."

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, co-author and director of the Department of Human Evolution at the Max Planck Institute in Leipzig, 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 are in agreement with recent genetic studies that show changes in genes related to brain development in our lineage since the population split between Homo sapiens and Neandertals. They add to the 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.
-end-
Original publication

Simon Neubauer, Jean-Jacques Hublin, Philipp Gunz
The evolution of modern human brain shape.
Science Advances; 24 January, 2018

Max-Planck-Gesellschaft

Related Evolution Articles:

Prebiotic evolution: Hairpins help each other out
The evolution of cells and organisms is thought to have been preceded by a phase in which informational molecules like DNA could be replicated selectively.
How to be a winner in the game of evolution
A new study by University of Arizona biologists helps explain why different groups of animals differ dramatically in their number of species, and how this is related to differences in their body forms and ways of life.
The galloping evolution in seahorses
A genome project, comprising six evolutionary biologists from Professor Axel Meyer's research team from Konstanz and researchers from China and Singapore, sequenced and analyzed the genome of the tiger tail seahorse.
Fast evolution affects everyone, everywhere
Rapid evolution of other species happens all around us all the time -- and many of the most extreme examples are associated with human influences.
Landscape evolution and hazards
Landscapes are formed by a combination of uplift and erosion.
New insight into enzyme evolution
How enzymes -- the biological proteins that act as catalysts and help complex reactions occur -- are 'tuned' to work at a particular temperature is described in new research from groups in New Zealand and the UK, including the University of Bristol.
The evolution of Dark-fly
On Nov. 11, 1954, Syuiti Mori turned out the lights on a small group of fruit flies.
A look into the evolution of the eye
A team of researchers, among them a zoologist from the University of Cologne, has succeeded in reconstructing a 160 million year old compound eye of a fossil crustacean found in southeastern France visible.
Is evolution more intelligent than we thought?
Evolution may be more intelligent than we thought, according to a University of Southampton professor.
The evolution of antievolution policies
Organized opposition to the teaching of evolution in public schoolsin the United States began in the 1920s, leading to the famous Scopes Monkey trial.

Related Evolution Reading:

Best Science Podcasts 2019

We have hand picked the best science podcasts for 2019. Sit back and enjoy new science podcasts updated daily from your favorite science news services and scientists.
Now Playing: TED Radio Hour

Climate Crisis
There's no greater threat to humanity than climate change. What can we do to stop the worst consequences? This hour, TED speakers explore how we can save our planet and whether we can do it in time. Guests include climate activist Greta Thunberg, chemical engineer Jennifer Wilcox, research scientist Sean Davis, food innovator Bruce Friedrich, and psychologist Per Espen Stoknes.
Now Playing: Science for the People

#527 Honey I CRISPR'd the Kids
This week we're coming to you from Awesome Con in Washington, D.C. There, host Bethany Brookshire led a panel of three amazing guests to talk about the promise and perils of CRISPR, and what happens now that CRISPR babies have (maybe?) been born. Featuring science writer Tina Saey, molecular biologist Anne Simon, and bioethicist Alan Regenberg. A Nobel Prize winner argues banning CRISPR babies won’t work Geneticists push for a 5-year global ban on gene-edited babies A CRISPR spin-off causes unintended typos in DNA News of the first gene-edited babies ignited a firestorm The researcher who created CRISPR twins defends...