Man's ancient ancestors had an ape-like brain structure but human-like brain growth, according to new research.
The claim is based on an analysis of eight skulls belonging to Australopithecus afarensis, the species to which the famous human ancestor 'Lucy' belongs.
Researchers consider the "mosaic" of ape and human features to be "a hallmark of evolution".
Lead author Philipp Gunz, a biological anthropologist at the Max Planck Institute for Evolutionary Anthropology in Germany, said: "Our data shows that Australopithecus afarensis had a more ape-like brain that nevertheless developed over a longer period of time, similar to modern humans."
An international team of scientists, which included researchers from the Natural History Museum in London and University College London, used state-of-the-art scanning technology to examine the three-million-year-old skulls, collected from archaeological sites Dikika and Hadar in Ethiopia.
The findings were published in the Science Advances journal.