Crania mismeasured by Morton with shot [10], using our measurements as the “gold standard.”

Our capacity measurements (“Current”) have been adjusted to account for the average difference (about 4%) produced by the difference in our method versus Morton's shot method (see Text S2). “Difference” is Morton's measurement relative to ours. Specimens with a percentage difference of greater than 5.5% (more than 2.5 standard deviations from the mean percentage difference) are clear outliers and we consider them to have been mismeasured by Morton. “Measure Error” is our measurement error based on three repeated measurements of each cranium's capacity.