Three-dimensional models of hominoid skulls used in the study – (a) Hylobates lar; (b) Pongo pygmaeus; (c) Pan troglodytes; (d) Gorilla gorilla; (e) Australopithecus africanus; (f ) Paranthropus boisei; (g) Homo sapiens. They have been scaled to the same surface area, and the colors denote areas of stress (blue = minimal stress, pink = high stress). From Wroe et al, 2010.

It is all too easy to think of human evolution in linear terms. From our 21st century vantage point we can look back through Deep Time for the first glimmerings of the traits we see in ourselves, and despite what we have come to know about the undirected, branching pattern of evolution, the origin of our species