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Figure 6: Jones, S., Martin, R. and Pilbeam, D. (1992) The Cambridge Encyclopaedia of Human Evolution, Cambridge University Press
Figure 6 (a) change in brain size (volume) in early and modern-day humans. (b) Plot of changes in body mass over the same period. The arrows indicate modern-day values. Given the approximations involved, the individual points are unreliable, but the trends are probably representative. Estimates of body mass of fossil species were derived from measurements of the length of long bones and are subject to error. (Note the unusual horizontal scale here, showing millions of years ago; the values increase from right to left - a pattern you may not have seen before.)