Old World Monkey Brains may Have Evolved Complexity Before Size

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Justine Alford

Guest Author

936 Old World Monkey Brains may Have Evolved Complexity Before Size
Professor Fred Spoor/UCL & Max Planck Institute for Evolutionary Anthropology

Almost 20 years on from its headline-making discovery as the most ancient Old World monkey skull ever discovered, the famous 15-million-year-old fossil has made the news once again.

Using a combination of sophisticated imaging techniques, scientists have managed to reconstruct the specimen’s brain, which revealed some unexpected features. Not only was it far smaller than anticipated, but it was surprisingly wrinkly; significantly more so than would have been expected for its modest size.  


That’s an exciting find, because it adds weight to the idea that size does not necessarily have to evolve before complexity when it comes to the brains of primates, meaning the two can evolve independently. The results have been published in Nature Communications (open access).

Old World monkeys, as the name suggests, are those from the Old World, meaning Africa and Asia. This particular specimen, belonging to Victoriapithecus, holds great scientific importance because it’s the only complete skull that scientists have so far managed to find for early cercopithecoids, the group comprising the Old World monkeys. It’s also the oldest, and fossils from this period are extremely scarce, so it’s key to our understanding of how their brains changed over time.

Obviously, the brain is no longer inside this 15-million-year-old skull, but scientists can gain a decent idea of what it looked like by creating 3D models with the use of X-ray imaging and CT scans. After doing so, scientists were also able to calculate its brain volume, which was found to be a humble 36 cubic centimeters. That’s less than half the volume of those belonging to modern-day species of a similar body size.

But size is not everything; the architecture was surprisingly complex, displaying a high level of folding and wrinkling. Furthermore, the area involved in the perception of smell – the olfactory bulb – was significantly larger than anticipated.


“It probably had a better sense of smell than many monkeys and apes living today,” study author Lauren Gonzales from Duke University said in a statement.

“In living higher primates you find the opposite: the brain is very big, and the olfactory bulb is very small, presumably because as their vision got better their sense of smell got worse. But instead of a tradeoff between smell and sight, Victoriapithecus might have retained both capabilities,” she added.

What is also intriguing is that its combination of small size and wrinkled architecture suggests that, at least for this branch of the primate family tree, complexity may have come before expansion, which is the reverse of what is generally believed to have occurred in our own lineage. 


  • tag
  • evolution,

  • brain,

  • primate,

  • olfactory bulb,

  • old world monkey