A tiny skull fossil suggests primate brain areas evolved separately
Digital reconstruction hints that the organ’s development over time was complicated
By Bruce Bower
A 20-million-year-old monkey skull that fits in the palm of an adult’s hand may contain remnants of piecemeal brain evolution in ancient primates.
Neural landmarks preserved on the skull fit a scenario in which specific primate brain regions expanded or, at times, contracted while other regions remained unchanged, a new study finds. In an early clue to that evolutionary process, researchers say, a small part of the monkey’s brain devoted to odor perception was not counterbalanced by an enlarged visual system, as is typical of primates today.
Primate visual systems expanded in size and complexity over millions of years without requiring substantial changes elsewhere in the brain, contend paleontologist Xijun Ni of the Chinese Academy of Sciences in Beijing and colleagues. And comparisons of the skull with fossils of African primates from 30 million years ago or more indicate that major brain structures evolved at different rates in different primate lineages, as did increases in brain size relative to body size, the team reports August 21 in Science Advances.
The study adds evidence to the idea that the brains of primates, a group that includes humans, evolved in a piecemeal way, instead of progressively getting bigger overall as time passed.