The development of the first detailed images of a 54-million-year-old primitive primate brain has been done by scientists at the Florida Museum of Natural History, and the University of Winnipeg, US, unexpectedly revealing that cousins of our earliest ancestors relied on smell more than sight.
According to a report in Natural History Magazine, the analysis of the well-preserved skull from 54 million years ago contradicts some common assumptions about brain structure and evolution in the first primates.
The study also narrows the possibilities for what caused primates to evolve larger brain sizes.
The skull belongs to a group of primitive primates known as Plesiadapiforms, which evolved in the 10 million years between the extinction of the dinosaurs and the first traceable ancestors of modern primates.
The 1.5-inch-long skull was found fully intact, allowing researchers to make the first virtual mold of a primitive primate brain.
"Most explanations on the evolution of primate brains are based on data from living primates," said lead author Mary Silcox, an anthropologist at the University of Winnipeg and research associate at the Florida Museum.
"There have been all these inferences about what the brains of the earliest primates would look like, and it turns out that most of those inferences are wrong," she added.
Researchers used CT scans to take more than 1,200 cross-sectional X-ray images of the skull, which were combined into a 3-D model of the brain.
"A large and complex brain has long been regarded as one of the major steps that sets primates apart from the rest of mammals," said Florida Museum vertebrate paleontologist and study co-author Jonathan Bloch.
"At our very humble beginnings, we weren't so special. That happened over tens of millions of years," he added.
"The animal, Ignacius graybullianus, represents a side branch on the primate tree of life," Bloch said.
"You can think of it as a cousin of the main line lineage that would have given rise ultimately to us," he added.