The brains of a large group of monkeys began to change around 15 million years ago as they evolved to cope with different environments and spend more time on the ground, according to a new study from The Australian National University (ANU).   

The study compared fossil skulls dating back 36 million years to the brains of present-day monkeys.  It focused on Old World monkeys – a group which includes species like baboons, macaques and mandrills.  

The study showed the temporal lobe – the part of the brain responsible for things like memory and communication – was smaller in the early monkeys.   

According to lead author and ANU PhD candidate Alannah Pearson, this started to change around 15 million years ago, when the temporal lobe began to scale up to match an increase in brain size in most species.   

“The temporal lobe helps monkeys remember different calls from their own species, or detect sounds from dangerous predators,” Ms Pearson said.   

36 million years ago, parts of Africa were very wet and tropical, but as it became drier and tropical areas disappeared, a lot of Old World monkeys adjusted to spend more time on the ground in woodland areas. 

This change in environment meant the monkeys also had to rely heavily on the temporal lobe for things like recognising where their new territory ended.  

“Group sizes also got bigger, so they needed to communicate with more individuals and remember more faces,” Ms Pearson said.   

“A larger temporal lobe is useful for spotting individuals that aren’t part of your troop.”  

Some species, like baboons, adapted to only live mostly on the ground, while others, like the macaques, started to spend time both in the trees and on the ground.  

Ms Pearson used CT scans to create three-dimensional versions of the skulls of the various species.  They all showed similar patterns.  

“The brain doesn’t survive in fossil records, so we used a cast of the inside of the skull to end up with a 3D representation – what’s known as an endocast,” Ms Pearson said.  

The study has been published in The Journal of Mammalian Evolution. 

Top image:  Paul/stock.adobe.com

Contact the media team

Jess Fagan

Media Manager


You may also like

Article Card Image

Mice surprise: researchers discover new native mammal species

Australia can now lay claim to two new species of native rodent thanks to an ANU-led study.

Article Card Image

Monster black hole devouring one sun every day

The fastest-growing black hole ever recorded – devouring the equivalent of one sun every day – has been discovered by ANU researchers.

Article Card Image

World-leading ANU scientists take up key advisory roles

Two exceptional ANU scientists have been appointed to leading Australian science organisations.  

Subscribe to ANU Reporter

Anu Logo

+61 2 6125 5111

The Australian National University, Canberra

CRICOS Provider: 00120C

ABN: 52 234 063 906

EDX Logo
APRU Logo
IARU Logo
Group of eight Australia Logo