Scan of 15 Million Year Old Monkey Skull Reveals Ancient Monkey Had Smaller Brain

Posted on July 7, 2015

Scientists have used high-resolution X-ray imaging to scan a 15 million year old monkey skull. The skull of the ancient monkey, Victoriapithecus, was discovered in Kenya's Lake Victoria in 1997. The X-ray imaging reveals that the ancient monkey had a smaller brain than modern monkeys.

Scientists also say the wrinkled brain revealed that cerebral complexity can evolve before brain size in primates. The scientists say the Victoriapithecus had a tiny brain relative to its body. It had a brain volume of about 36 cubic centimeters. This is less than half the brain volume of modern monkeys of a similar size. The researchers say in a statement, "If similar-sized monkeys have brains the size of oranges, the brain of this particular male was more akin to a plum."

The CT scans of the ancient monkey skull also revealed a complex brain with numerous distinctive wrinkles and folds. It also revealed the olfactory bulb was three times larger than expected.

Lauren Gonzales of Duke University, a co-author if the study, says, "It probably had a better sense of smell than many monkeys and apes living today. 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."

A research paper on the scan of the ancient monkey skull can be found here in the journal, Nature Communications.