Evolutionary Theory and the Global Warming Hypothesis: A World (of Evidence) Apart

A recent story in the New York Times draws attention to recent legislative attempts by creationists to force public schools to “teach the controversy” between evolution and creationism, and between the man-made global warming hypothesis and criticisms of it.

Two recent developments have pushed the creationists to draw parallels between the controversies. First, attempts to enforce the view that evolution is “only a theory” have been struck down on the grounds of church/state separation. (The court noted that no other scientific theory of equal evidential status has been singled out for such demotion.) Second, the recent “ClimateGate” scandal—in which hacked emails from the Climate Research Unit at the University of East Anglia revealed what appears to be evidence of a conspiracy to fudge and suppress data—has raised fresh doubts about the veracity of the climate science behind the recent push to regulate carbon emissions.

On the question of whether doubts about evolution and those about man-made global warming are justified, the Times article reveals a remarkable degree of agreement between the pro- and anti-evolution camps. According to John G. West of the Discovery Institute, which promulgates creationism, “There is a lot of similar dogmatism on this issue. . . . We think analyzing and evaluating scientific evidence is a good thing, whether that is about global warming or evolution.” On the other side, Lawrence M. Krauss, a pro-evolution physicist at Arizona State University, “described the move toward climate-change skepticism as a predictable offshoot of creationism.” Says Krauss:

Wherever there is a battle over evolution now [. . .] there is a secondary battle to diminish other hot-button issues like Big Bang and, increasingly, climate change. It is all about casting doubt on the veracity of science—to say it is just one view of the world, just another story, no better or more valid than fundamentalism.

Both sides are right to some degree. “Many scientists” agree with both evolutionary theory and the theory of man-made global warming. As the Times summarizes it: 

For mainstream scientists, there is no credible challenge to evolutionary theory. They oppose the teaching of alternative views like intelligent design, the proposition that life is so complex that it must be the design of an intelligent being. And there is wide agreement among scientists that global warming is occurring and that human activities are probably driving it.

But suppose for the moment that every scientist on the planet expressed belief in both theories. Suppose further that as laymen, we have no way of assessing all of the technical details of each theory. Could we nevertheless identify differences between the quality of the evidence scientists appeal to in support of their theories?

Even moderately educated adults know (or could readily learn) that Darwin’s theory of evolution by natural selection is based on a vast array of evidence accumulated over more than a century and a half of investigation. It integrates observations from a variety of disparate scientific disciplines: Linnaeus’ taxonomy of the species, Lyell’s geology, Malthus’ population dynamics, as well as Darwin’s own collection of data from biogeography, paleontology, comparative anatomy, comparative embryology, and common sense observations about the success of dog breeders. And following Darwin’s own work, which integrated all of that, other scientists discovered further evidence in support of his theory—evidence such as later 20th-century discoveries in biochemistry that accounted for the mechanism by which evolved traits are passed on to descendents.

Compare such evidence to the evidence supporting the hypothesis of man-made global warming. A simple first pass indicates that the theory is relatively young compared to Darwin’s: Scientists have only considered it seriously for the last thirty years. Even now, the data alleged to support the theory is poor compared to the plethora of evidence in support of evolution. The most direct data scientists have about temperature extends back only about 100 years; the rest of their evidence is itself a product of inference based on ice cores and tree rings. And scientists do not yet clearly understand the role of CO2 as a factor contributing to temperature change. Many say there is evidence suggesting that other factors, such as sunspots, may play a bigger role.

Whatever the merits of the hypothesis of man-made global warming, it cannot claim the evidential virtues of the theory of evolution. Evolution by natural selection is the central integrating principle of the entire field of biology. As evolutionary biologist Theodosius Dobzhansky put it, “Nothing in biology makes sense except in the light of evolution.” The hypothesis of man-made global warming is far from central to climate science, and could be dispensed with without altering our understanding of other climate principles.

Even leaving aside questions about the comparative quality and comprehensiveness of the evidence behind each theory, there is an additional factor that could lead us rationally to doubt one theory but not the other: the factor of ideological and political motivation.

Acceptance of evolutionary theory does not serve any ordinary or obvious political agenda. Each side of the political spectrum has attempted to lay claim to the theory, whether Herbert Spencer’s social Darwinist argument for laissez-faire, or Peter Singer’s invocation of a “Darwinian Left.”

Contrast this with man-made global warming hypothesis—a thesis advanced after our culture had been steeped for decades in environmentalist and anti-capitalist ideology. Long before scientists considered the effect of carbon dioxide on temperature and human well-being, intellectuals had convinced themselves (and others) that capitalism is evil and that human material progress is an arrogant intrusion in nature. That a scientific theory consonant with this view is now being asserted—and that the scientists pushing the theory are funded by cultural and governmental institutions insistent upon further entrenching the environmentalist and anti-capitalist ideology—could easily appear too convenient to be a coincidence.

Even if the global warming hypothesis turns out to be true, given the comparative quality of evidence currently in support of it and the legitimate concern regarding motivations behind the theory, there are plenty of rational grounds to doubt the veracity of its advocates. This stands in stark contrast with evolutionary theory.

It is no surprise that creationists would exploit legitimate doubts about the hypothesis that human activity is causing global warming to cast doubt on completely legitimate science: As advocates of faith, they are critical of the scientific method as such. But it is also not surprising that die-hard defenders of the hypothesis would attempt to smear all critics of their view as akin in motivation to creationists: They have already attempted the same smear job by labeling critics of global warming as “denialists,” likening them to Holocaust deniers—as if the certainty of man-made global warming were on par with the occurrence of the Holocaust.

Both of these groups are on the non-objective premise of finding ways to criticize everything believed by an opposing group. The consensus of modern scientists, in their view, is either all up for doubt or all sacrosanct. But the hallmark of objectivity in this context is the ability to evaluate as true or false different components of a theory or hypothesis. Considering the genuine difference in the evidential status between evolutionary theory and the man-made global warming hypothesis, all interested parties should insist on such objectivity.

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