Old World Monkey Oldest Skull Shows Small Brain

Posted: Jul 7 2015, 9:31am CDT | by , in Latest Science News


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Old World Monkey Oldest Skull Shows Small Brain
Photo courtesy of Fred Spoor of the Max Planck Institute for Evolutionary Anthropology.
  • Ancient Monkey Skull 3D reconstruction reveals small brain in specimen

Researchers have reconstructed the inside of a fossilized skeleton of a brain of an earlier species of a monkey found in 1997 which revealed a smaller and complex brain.

The fossilized remains of Victoriapithecus skull made a great specter in the headlines when it was discovered in 1997 in Kenya’s Lake Victoria. Sai to have lived 15 million years ago, the monkey’s remains were a great source of speculation for researchers from various fields.

With the advance in technology, the researchers have currently peaked inside the cranial cavity with the help of high resolution imaging which has in turn aided in construction of a visual image of the brain. Micro CT scans then revealed that the Victoriapithecus had a tiny brain relative to its body size thus proving the hypothesis that brain complexity can evolve before brain size in the primate family tree.

Fred Spoor of the Max Planck institute for Evolutionary Anthropology and Lauren Gonzales of Duke University, calculated the volume of the brain which came out to be 36 cubic centimeters, almost half the volume of the monkeys living today.

Brenda Benefit from New Mexico State University who discovered the remains with Monte McCrossin of NMSU, said that Lauren told her that she would not believe what the brain looked like. For comparison, the authors said that if the brain of the modern monkey was the size of an orange than the size of Victoriapithecus can be the size of 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.

Despite its small size, the brain structure is very complex. It had numerous wrinkles and folds with an additional size of the olfactory bulb which was indicative of a highly evolved sense of smell in the older primate. It was also proposed that the modern monkey lost its acute sense of smell in favor of sight. Even then the Victoriapithecus seems to have retained both senses equally.

"It probably had a better sense of smell than many monkeys and apes living today," Gonzales said. "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," Gonzales said.

"This is the oldest skull researchers have found for Old World monkeys, so it's one of the only clues we have to their early brain evolution," Benefit said.

The fossil findings are a revelation in the field of hypothesized discussions of the size decrease of the primates across time whilst the findings prove otherwise. The authors also highlighted that these findings are in support of the brain size of Homo foresciensis, human ancestors that lived fifteen thousand years ago and the remains of whom were found in Indonesia in 2003, were said to have smaller brain sizes.

"In the part of the primate family tree that includes apes and humans, the thinking is that brains got bigger and then they get more folded and complex," Gonzales said. "But this study is some of the hardest proof that in monkeys, the order of events was reversed -- complexity came first and bigger brains came later."

"Brain size and brain complexity can evolve independently; they don't have to evolve together at the same time," Benefit said.

The study has been published in July 3rd edition of Nature Communications.

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