Michael Weisberg | University of Pennsylvania

Remeasuring Man Michael Weisberg | University of Pennsylvania Morton’s Cranial Collection Were Morton′s Measurements Racially Biased? Sexual Dimorphism Samuel George Morton (1799 – 1851) was the greatest American Despite labeling the crania by sex, Morton never computed scientist of the early 19th century. Tanks largely to Stephen Jay Samuel Morton used white peppercorns for the measurements reported in diferent averages for males and females. Gould, Morton’s cranial capacity measurements of diferent races Crania Americana. He was unhappy with these measurements, which he took is now held up as a prime example of and cautionary tale against to be inaccurately small and of high variance. For subsequent work, he scientifc racism. A team of anthropologists recently reevaluated remeasured the original sample using lead shot. If Morton’s errors were due Morton’s work and argued that it was Gould, not Morton, who to the peppercorns alone, the under-measurement should have been the M 86.5 was biased in his analysis. Tey are mistaken. same for each race — but it wasn’t! 83.3 F 77.2 Mean Cranial Capacity Reported in Crania Americana (1839) and Crania Aegyptiaca (1844) 79.0 M 87.5 90 F 75.5 89.53 “[The Caucasian race] is distinguished for 87.00 84 the facility with which it attains the Morton’s Negroid males are larger than his Caucasian males. 83.44 highest intellectual endowments.” 81.97 Human Diversity in Five Races 79.75 — Samuel Morton, 1839 Notable Specimens 78 78.00 Morton’s wanted to apply the methods of natural history to “Plausible scenarios are easy to construct Morton had special interests in Native American Mound human variation. He categorized human diversity using racial Builders, Americans with manipulated skull shapes, European types, dividing humans into fve races: Caucasian, American, 71 …[he] takes a distressingly small notables, “Idiots,” and criminals. Malay, Mongolian, and Ethiopian (African). His map of racial Caucasian skull, shakes hard, and pushes distribution is shown below. Inches Capacity in Cubic Canial mightily at the foramen magnum with 65 Caucasian American African his thumb.” Crania Americana Crania Aegyptiaca — Stephan Jay Gould, 1981 2011 Remeasurement of Morton’s Crania Lewis et al. remeasured 46% of Morton’s collection with precision plastic balls. Tey found that only 2% of their measurements difered signifcantly from those reported in Crania Americana. “These results falsify the claim that Morton physically mismeasured crania based on his a priori biases.” — Lewis et al., 2011 Measuring Man References Gould’s Main Argument is Correct Gould correctly claimed: Morton believed that cranial capacity, the volume of the interior Gould argued that the diferences between the peppercorn-based and shot- Gould, Stephen J. (1978). Morton’s ranking of races by cranial capacity. Science 200(4341), • Morton selectively mismeasured with 503-509. of the cranium, was a proxy for brain size and for intelligence. He based measurements reveal Morton’s biases. Although Lewis et al. showed peppercorns, which gives evidence that assessed this capacity by flling skulls with peppercorns or lead that Morton’s shot-based measurements are reliable, this cannot defeat Gould, Stephen J. (1996). Te mismeasure of man. Second edition. New York: WW Norton Morton’s measurements were racially biased. & Company. shot, and then measured the resulting volume. Gould’s argument. Tey would have to show that Morton’s peppercorn- Lewis, J. E., DeGusta, D., Meyer, M. R., Monge, J. M., Mann, A. E., & Holloway, R. L. based measurements were accurate. Systematic diferences in the means is • Sexual dimorphism is a source of bias that (2011). Te mismeasure of science: Stephen Jay Gould versus Samuel George evidence of systematic measurement error. Tis systematic error could be the Morton didn't address. Morton on skulls and bias. PLoS Biology 9(6). result of racial bias. Morton, Samuel George (1839). Crania Americana or, a Comparative View of the Skulls of • Tere is little diference in cranial capacity Various Aboriginal Nations of North and South America. Philadelphia: John between Morton’s races. Pennington. Morton, Samuel George (1844). Crania Aegyptiaca. Or, Observations on Egyptian Gould’s critique of Morton Ethnography, Derived from Anatomy, History, and the Monuments. Gould mistakenly claimed: Morton, Samuel George (1849). Catalogue of Skulls of Man and the Inferior Animals. Philadelphia: Merrihew and Tompson. has been widely cited as an • Tere are no diferences at all between crania of diferent races. illustration of bias in science; Many thanks to Sam Cox, Elihu Gerson, Robert • Native Americans have the largest crania in Jones, Paul Mitchell, Janet Monge, Deena Skolnick Weisberg, and Michael Yudell for feedback on this it ought to remain so. the collection. project. Some photos courtesy of Brett Calcott and Penn Museum..

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