Human and gorilla brains. Historical artwork comparing the brain sizes of an early human and a gorilla. The scale is in millimetres, the brains are seen side on, and the front of the brain is at left. The smaller gorilla brain is superimposed on the human brain, and brain anatomy is labelled. Artwork from 1931, when comparisons like this were used to decide whether the fossils being discovered at this time were of humans, apes, or an evolutionary link. This human brain is smaller than modern human brains, and is based on the Gibraltar skull (discovered 1848), later identified as a specimen of Neanderthal Man (Homo neanderthalensis). Artwork from New Discoveries relating to The Antiquity of Man (Sir Arthur Keith, 1931).