"The brain is often thought of as what distinguishes humanity from the rest of the animal kingdom, and the juvenile specimen of Au. sediba had an exceptionally well-preserved skull that could shed light on the pace of brain evolution in early hominins. To find out more, the researchers scanned the space in the skull where its brain would have been using the European Synchrotron Radiation Facility in Grenoble, France; the result is the most accurate scan ever produced for an early human ancestor, with a level of detail of up to 90 microns, or just below the size of a human hair.

The scan revealed Au. sediba had a much smaller brain than seen in human species, with an adult version maybe only as large as a medium-size grapefruit. However, it was humanlike in several ways — for instance, its orbitofrontal region directly behind the eyes apparently expanded in ways that make it more like a human's frontal lobe in shape. This area is linked in humans with higher mental functions such as multitasking, an ability that may contribute to human capacities for long-term planning and innovative behavior.

"We could be seeing the beginnings of those capabilities," researcher Kristian Carlson at the University of Witwatersrand told LiveScience.

These new findings cast doubt on the long-standing theory that brains gradually increased in size and complexity from Australopithecus to Homo. Instead, their findings corroborate an alternative idea — that Australopithecus brains did increase in complexity gradually, becoming more like Homo, and later increased in size relatively quickly."