Tuesday, June 14, 2011

The Mismeasure of Stephan Jay Gould

In his widely read and influential 1981 book "The Mismeasure of Man" Stephan Jay Gould, Harvard paleontologist, evolutionary biologist and historian of science, accused a previous scientist, 19th-century physical anthropologist Samuel George Morton, of fudging the data that suggested that different races had different average brain sizes. A new study, using the same skulls as Morton, showed that the original study, as performed, was accurate.

Dr. Gould, who died in 2002, based his attack on the premise that Morton believed that brain size was correlated with intelligence. But there is no evidence that Morton believed this or was trying to prove it, said Jason E. Lewis, the leader of the Pennsylvania team. Rather, Morton was measuring his skulls to study human variation, as part of his inquiry into whether God had created the human races separately (a lively issue before Darwin decreed that everyone belonged to the same species).

In his book, Dr. Gould contended that Morton’s results were “a patchwork of fudging and finagling in the clear interest of controlling a priori convictions.” This fudging was not deliberate, Dr. Gould said, but rather an instance of unconscious doctoring of data, a practice he believed was “rampant, endemic and unavoidable” in science. His finding is widely cited as an instance of scientific bias and fallibility.

But the Penn team finds Morton’s results were neither fudged nor influenced by his convictions. They identified and remeasured half of the skulls used in his reports, finding that in only 2 percent of cases did Morton’s measurements differ significantly from their own. These errors either were random or gave a larger than accurate volume to African skulls, the reverse of the bias that Dr. Gould imputed to Morton.

“These results falsify the claim that Morton physically mismeasured crania based on his a priori biases,” the Pennsylvania team writes.
Ironically, Gould was guilty of the same scientific crime he imputed to Morton, allowing his biases to direct his research, and then doing shoddy work to achieve the results he desired:
Dr. Gould did not measure any of the skulls himself but merely did a paper reanalysis of Morton’s results. He accused Morton of various subterfuges, like leaving out subgroups to manipulate a group’s overall score. When these errors were corrected, Dr. Gould said, “there are no differences to speak of among Morton’s races.”

But Dr. Gould himself omitted subgroups in his own reanalysis, and made various errors in his calculations. When these are corrected, the differences between the racial categories recognized by Morton are as he assigned them. “Ironically, Gould’s own analysis of Morton is likely the stronger example of a bias influencing results,” the Pennsylvania team writes.

Dr. Lewis, the lead author, said that on checking the references for some of Dr. Gould’s accusations he found that Morton had not made the errors attributed to him. “Those elements of Gould’s work were surprising,” he said. “I can’t say if they were deliberate.”
Obviously, much of Morton's original material still exist, and if Gould had pursued debunking Morton with those materials, he might have come to a different conclusion.  And he should have been aware of the likely continued existence of these materials, in addition to Harvard, he also worked for the American Museum of Natural History in New York, home of many great collections.

This in no way serves to lessen the Gould's impacts on the field of evolution; his theory of punctuated equilibrium is now one of the lynch pins of evolutionary theory.  But it does suggest how even a great scientist can be mislead when he let his biases get out ahead of his research.

Seen first at Althouse.

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