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Gorilla skull. Coloured X-ray of the skull of a male gorilla (^IGorilla gorilla^i), in lateral view. Three subspecies of this large ape inhabit forests in central and western Africa. It is the largest living primate. Its skull differs from that of a human in having more pronounced brows, thicker bones and a far smaller cranial capacity (hence gorillas have smaller brains than humans). Male gorillas have a pronounced sagittal crest on the top of their skulls (upper right), which is where the muscles that work the large and powerful jaws (lower left) attach. The teeth are used for grinding their food of plants, and are used by males in displaying and competing for females. (KEYSTONE/SCIENCE PHOTO LIBRARY/D. ROBERTS/SCIENCE PHOTO LIBRARY)