Primates evolved larger brains to hop between trees

Washington, July 1 (ANI): A new study, in which scientists scanned a 54-million-year-old skull roughly the size of a walnut, has suggested that primates such as lemurs, monkeys, apes, and humans might have evolved larger brains as a result of the need to move quickly from tree to tree.

According to a report in National Geographic News, the 1.5-inch-long (4-centimeter-long) skull belongs to the long-gone Ignacius graybullianus, described as a cousin of our earliest ancestors, which arose less than ten million years after the dinosaurs vanished.

Discovered in Wyoming roughly 25 years ago, the fossil "is the most complete early primate skull known," said study co-author Jonathan Bloch, a vertebrate paleontologist at the University of Florida.

Due to its completeness and age, the skull gives us the clearest idea yet what early primates were like, according to the researchers.

After taking more than 1,200 detailed X-ray images of the skull, researchers combined them to help create a 3-D model of Ignacius' brain.

The model showed a brain just one-half to two-thirds the size of the smallest modern primate brain, the study said.

It seems that such a small brain was enough for tree dwelling and fruit seeking.

Ignacius' teeth, for example, suggest it had a fruit diet, while the animal's claws and flexible joints hint at tree dwelling.

The finding therefore reopens the question of what triggered the evolution of large brains in later primate species, if not branch living or fruit eating?

One activity Ignacius seems unsuited for is jumping from tree to tree, as opposed to simply climbing branches.

In primates, this type of leaping generally requires long hind limbs, large inner-ear organs linked to balance-and strong visual processing.

Instead of a robust center of vision, Ignacius' brain had large lobes dedicated to smelling, the model suggests.

The prehistoric primate "was mostly a nose-first animal that relied on smell instead of sight, unlike modern primates, which have far more developed visual processing areas," explained lead study author Mary Silcox, a vertebrate paleontologist at the University of Winnipeg.

"For primates, stepping up vision would have been key for leaping safely," she surmised.

But, to do that, the brain had to be larger, which eventually happened as a result of evolution. (ANI)