The Believing Brain - Michael Shermer [181]
To be sure, not all claims are subject to laboratory experiments and statistical tests. There are many historical and inferential sciences that require nuanced analyses of data and a convergence of evidence from multiple lines of inquiry that point to an unmistakable conclusion. Just as detectives employ the convergence of evidence technique to deduce who most likely committed a crime, scientists employ the method to deduce the likeliest explanation for a particular phenomenon. Cosmologists reconstruct the history of the universe through a convergence of evidence from cosmology, astronomy, astrophysics, spectroscopy, general relativity, and quantum mechanics. Geologists reconstruct the history of the earth through a convergence of evidence from geology, geophysics, and geochemistry. Archaeologists piece together the history of a civilization from pollen grains, kitchen middens, potsherds, tools, works of art, written sources, and other site-specific artifacts. Environmental scientists reconstruct climate history through the environmental sciences, meteorology, glaciology, planetary geology, geophysics, chemistry, biology, ecology, and others. Evolutionary biologists uncover and explain the history of life through geology, paleontology, botany, zoology, biogeography, comparative anatomy and physiology, genetics, etc.
Even though these inferential sciences do not fit the model of experimental laboratory sciences, hypothesis testing can be employed nevertheless. Indeed, scientists working within such historical sciences must test hypotheses in order to avoid the confirmation bias, the hindsight bias, and many other cognitive biases that will surely color their interpretations of the data. As Frank Sulloway noted at the end of his scientific treatise on the psychology of history: “When the mind is confronted with more information than it can absorb, it looks for meaningful (and usually confirmatory) patterns. As a consequence, we tend to minimize evidence that is incongruous with our expectations, causing the dominant worldview to bring about its own reaffirmation.” In fact, Sulloway suggests that Charles Darwin may well be the greatest historian who ever lived because he went out of his way to test his hypotheses about the history of life, and this became the foundation of his work culminating in On the Origin of Species, which revolutionized his field, changing it from genteel speculations by amateur naturalists to the rigorous science it is today. Darwin even employed his new science to the history of his own life, as Sulloway explains: “Charles Darwin understood this human predilection for reaffirming the status quo. In his Autobiography he noted how quickly he tended to forget any fact that seemed to contradict his theories. He therefore made it a ‘golden rule’ to write this information down so that he would not overlook it. Like Darwin’s golden rule, hypothesis testing overcomes certain limitations in how the human mind processes information.”3
Science and the Comparative Method
How do you test a historical hypothesis? One way is through the comparative method, which was brilliantly employed by UCLA geographer Jared Diamond in his book Guns, Germs, and Steel, in which he explained the differential rates of development between civilizations around the globe over the past thirteen thousand years.4 Why, Diamond asked, did Europeans colonize the Americas and Australia, rather than Native Americans and Australian Aborigines colonize Europe? Diamond rejected the hypothesis that inherited differences in abilities between the races precluded some groups from developing as fast as others. Instead Diamond proposed a biogeographical theory having to do with the availability of domesticated grains and animals to trigger the development of farming, metallurgy, writing, non-food-producing specialists, large populations, military and government bureaucracies, and other components that gave rise to Western cultures. Without these plants and animals, and a concatenation of other factors, none of these characteristics