The brain hidden inside the oldest known Old World monkey skull has been visualized for the first time. The creature's tiny but remarkably wrinkled brain supports the idea that brain complexity can evolve before brain size in the primate family tree. The ancient monkey, known scientifically as Victoriapithecus, first made headlines in 1997 when its fossilized skull was discovered on an island in Kenya's Lake Victoria, where it lived 15 million years ago. 

Now, thanks to high-resolution X-ray imaging, researchers have peered inside its cranial cavity and created a three-dimensional computer model of what the animal's brain likely looked like.

Micro-CT scans of the creature's skull show that Victoriapithecus had a tiny brain relative to its body. 

Co-authors Fred Spoor of the Max Planck Institute for Evolutionary Anthropology and Lauren Gonzales of Duke University calculated its brain volume to be about 36 cubic centimeters, which is less than half the volume of monkeys of the same body size living today. 

If similar-sized monkeys have brains the size of oranges, the brain of this particular male was more akin to a plum.

"When Lauren finished analyzing the scans she called me and said, 'You won't believe what the brain looks like,'" said co-author Brenda Benefit of New Mexico State University, who first discovered the skull with NMSU co-author Monte McCrossin.