By Dr. Robert Thorson

When celebrating the birthday of a 2-year-old, parents usually light two candles on the cake. When celebrating Darwin’s bicentennial birthday, it makes sense to write two columns. Here’s my second metaphorical candle written in his honor.

According to the latest national Gallup Poll on evolution (2007), nearly half of all Americans still do not believe in evolution. Darwin would be disappointed, but hardly surprised: He learned from gut-wrenching personal experience that accepting natural selection takes intellectual courage, as well as intellectual ability.

For the moment, nonbelievers have lost their legal fight to have creationist ideas taught in public school classrooms. But over the long haul, they’ve been overwhelmingly successful in delaying its teaching until later grades and watering the subject down in biology curriculums and textbooks. From my point of view, however, their most important success has been the virtual elimination of physical geology from the competitive high school track, and of historical geology from the non-college track. These subjects figured very prominently in Darwin’s most famous work, “The Origin of Species By Means of Natural Selection.”

This is self-evident from a simple word search of the full Guggenheim Project electronic text of the “Origin.” Enter the words “geological” and “geology,” and you will come up with 101 and 21 hits, respectively, one in the first sentence. Search for biology, zoology or botany, with or without their “- ical” suffix, and you will come up with nothing.

The connection between Darwin and geology is thoroughly documented by the historian Sandra Herbert in her award-winning book “Charles Darwin, Geologist.” She writes: “As a young man, Darwin was known both popularly and professionally as a geologist. In February 1859, the Geological Society awarded him its highest honor, the Wollaston Medal, for his signal contributions to the field.” At the time, he was 50 years old. Publication of the “Origin” was eight months hence.

Fossils? Egads! What a dangerous idea for the high school curriculum. Better skip that. Extinction? Yikes! Better skip that, too. Darwin’s contributions to the understanding of earthquake process, tectonic uplift, coral reefs, glacial erratics and invertebrate paleontology? No way! He couldn’t be right about all that and wrong about evolution. To downplay evolution, we must downplay the whole man.

The deep time of geology is the world’s second-most dangerous idea because it gave rise to the world first-most dangerous idea, natural selection. In the conclusion to the “Origin,” Darwin wrote: “The chief cause of our natural unwillingness to admit that one species has given birth to another and distinct species, is that we are always slow in admitting great changes of which we do not see the steps. The difficulty is the same as that felt by so many geologists, when [pioneering geologist Sir Charles] Lyell first insisted that long lines of inland cliffs had been formed, and great valleys excavated, by the agencies which we still see at work. The mind cannot possibly grasp the full meaning of the term of even a million years.”

Darwin took the deep time of geology and applied it not to the incremental transformation of a valley, but to the incremental transformation of living organisms, most famously to the finches of the Galapagos Islands.

The threat to creationism posed by deep time explains why the most hard-core nonbelievers are “young Earth creationists.” They insist that Earth is no more than about 6,000 years old, and spend their days trying to fit the mythos of Genesis into the logos of Earth system history, now 4.6 billion years in the making.

Of course, there are other reasons earth scienceis downplayed in the high school curriculum that have nothing to do with evolution. The competitive college-prep curriculum emphasizes the fundamental physical sciences of physics and chemistry, and the one humans have the most natural affinity for, which is biology. Curriculum gurus can be happy about this because it saves geology for those not on the college track who need to meet state-mandated science requirements.

But perhaps I’m wrong about this. Being an integrated composite of physics, chemistry, biology, planetary science and history, geology might just be too rock-hard to teach.