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Morton, Gould, and Bias: A Comment on “The Mismeasure of Science”

2016; Public Library of Science; Volume: 14; Issue: 4 Linguagem: Inglês

10.1371/journal.pbio.1002444

1545-7885

Michael Weisberg, Diane Β. Paul,

Zoonotic diseases and public health

famously used the work of Samuel George Morton (1799-1851) to illustrate how unconscious racial bias could affect scientific measurement.Morton had published measurements of the average cranial capacities of different races, measurements that Gould reanalyzed in an article in Science [1] and then later in his widely read book The Mismeasure of Man [2].During the course of this reanalysis, Gould discovered prima facie evidence of unconscious racial bias in Morton's measurements.More than 30 years later, Lewis et al. published a critique of this analysis [3], denying that Morton's measurements were biased by his racism.Instead, they claim that their "results falsify Gould's hypothesis that Morton manipulated his data to conform with his a priori views."We believe this is mistaken, and our comment will explain why.Morton was a Philadelphia physician and highly respected scientist who avidly collected and measured human skulls.Between 1830, when he began his collection, and his death in 1849, Morton had amassed over a thousand specimens, making his the largest collection of human skulls in the world.To measure cranial capacity (a proxy for brain size), Morton filled the cranial cavities with spherical materials: "white pepper seed" for his 1839 measurements and BB shot for his 1844 measurements.He then computed racial averages using the 5-fold classification-Caucasian, Mongolian, Malayan, Ethiopian, and American-invented by Johann Friedrich Blumenbach (1752-1840).He also computed averages for families and subfamilies within these racial groups.His measurements indicated that the "Teutonic Family" (consisting primarily of Germans, Anglo-Saxons, Anglo-Americans, and Anglo-Irish) within the modern Caucasian group had by far the largest brains.Gould's argument for Morton's unconscious racial bias is based on a comparison between two sets of measurements using two different materials.In his 1839 Crania Americana, Morton used "pepper seeds," but he switched technique to using lead BB shot for the measurements presented in his later works, especially the 1844 Crania Aegyptiaca.Morton made this switch because the pepper seeds were light, variable in size, and easily compressed, and as a result his measurements were highly variable.It is important to note that Gould agrees with Morton about the superiority of the shot measurements.Gould calls these measurements "objective, accurate, and repeatable" [2].After tabulating and reanalyzing Morton's data, Gould was struck by a systematic difference between the two sets of measurements.The mean cranial capacity for Africans, Americans, and Caucasians had all increased between 1839 and 1844, as is shown in Fig 1 .However, they did not change by the same amounts.The African skulls have a much larger increase in mean cranial capacity than the Americans and Caucasians.If this difference were the result either of lack of precision or of a systematic measurement error, the change should be approximately the same for the different races, but it was not.Gould thought that the best explanation for the