The Dikika girl had an estimated brain size of 330 cubic centimetres when she died, which is not very different from that of a similarly aged chimpanzee. However, when compared to the adult afarensis values, it forms 63 - 88% of the adult brain size.
This is lower than that of an adult chimp, where by the age of three, over 90% of the brain is formed. This relatively slow brain growth in the Dikika girl appears to be slightly closer to that of humans.
Slow, gradual development in an extended childhood is regarded as a very human trait - probably to enable our higher functions to develop.
