In his August 12 nationally syndicated column, Fox News host Tony Snow equated evolutionary theory to "intelligent design" (commonly referred to as ID), claiming that "[e]volutionary theory, like ID, isn't verifiable or testable. It's pure hypothesis." Specifically, he falsely asserted that no fossil evidence exists in support of evolutionary theory. In fact, there is significant support for evolutionary theory in the fossil record, just one of many pillars of evidence supporting evolutionary theory.
The theory of evolution maintains that increased complexity among organisms (the development of species) occurs through random genetic mutation and that organisms with characteristics best suited to their environment thrive -- the result of a process known as "natural selection." Conversely, "intelligent design" maintains that life on earth is far too complex to have arisen solely as a function of random genetic mutation and was instead designed by a supernatural "intelligence."
In his column, Snow claimed that "evolutionary theorists find themselves at wits' end because the fossil record provides no evidence of any species ever turning into another." In writing this, Snow invoked the idea of a "missing link" -- an organism whose features clearly demonstrate a transition from one species to another. This claim is false, however, and misstates the current understanding of evolutionary theory. Alan D. Gishlick, a post-doctoral scholar at the National Center for Science Education, wrote that " 'missing link' is an outdated term that does not accurately reflect the way biologists and paleontologists think about fossils."
Instead, Gishlick maintains, evolutionary scientists search for fossilized organisms with "transitional features," such as the archaeopteryx. A creature of the Jurassic period (150 million years BCE), Archaeopteryx lithographica possessed both avian and dinosaurian features. Like most dinosaurs, it had teeth, a flat sternum, and a bony tail; but it also had feathered wings and a furcula (wishbone) -- characteristics common to most birds. Of the few archaeopteryx fossils unearthed, the most complete and visually striking example is housed in Berlin's Humboldt Museum. Archaeopteryx is not a "missing link," nor can one conclusively assert that it is the ancestor of modern birds. It does, however, provide strong evidence that modern birds evolved from dinosaurs or reptiles.
Another famous example of a fossil with transitional features is "Lucy," the name given to the partial skeletal remains of a 3.2 million-year-old hominid found in Ethiopia in 1974. Classified Australopithecus afarensis, "Lucy" and her species were ape-like but were also determined to be bipedal -- a human characteristic. This finding was bolstered by the discovery of 3.6 million-year-old fossilized footprints of a bipedal hominid in Tanzania in 1976. Known as the Laetoli footprints, they are far more similar to the footprints of modern humans than they are to those of apes. Again, while not a 'missing link,' 'Lucy' and her ilk strongly indicate that modern humans and apes are descended from a common ancestor." *
Nevertheless, Snow went on to write: "Evolutionary theory, like ID, isn't verifiable or testable. It's pure hypothesis -- like ID -- although very popular in the scientific community. Its limits help illuminate the fact that hypotheses are only as durable as the evidence that supports them." In claiming that evolutionary theory is little more than a hypothesis, Snow is misusing scientific terms. Commonly used, "theory" can mean uninformed speculation or guesswork. Used scientifically, it means "a plausible or scientifically acceptable general principle or body of principles offered to explain phenomena," according to Merriam-Webster's online dictionary. The scientific method maintains that a hypothesis is a tentative explanation for patterns observed in collected data. A hypothesis becomes a theory after extensive testing and rigorous scrutiny.
Evolution is considered an established scientific theory because of the preponderance of evidence supporting it. Snow wrote that "hypotheses are only as durable as the evidence that supports them." Aside from the fossil record discussed above, which many scientists consider the most compelling support of evolutionary theory, there is additional evidence as well. A well-known example of evolution and natural selection in action is that of Darwin's finches. When naturalist Charles Darwin landed on the Galapagos Islands in 1835, he observed a variety of small finches that were similar in appearance, except for the shapes of their beaks. Each species of finch -- descendents of a common ancestor -- had adapted to their particular niche and developed a beak suited to their diet.
Science and Creationism, a book published by the National Academy of Sciences (NAS), documents more evidence in support of evolution -- such as physical and embryonic similarities among seemingly divergent species. The NAS also refutes Snow's assertion that evolutionary theory "isn't verifiable or testable." According to Science and Creationism:
Evolutionary theory explains that biological diversity results from the descendants of local or migrant predecessors becoming adapted to their diverse environments. This explanation can be tested by examining present species and local fossils to see whether they have similar structures, which would indicate how one is derived from the other. Also, there should be evidence that species without an established local ancestry had migrated into the locality. Wherever such tests have been carried out, these conditions have been confirmed.
Correction: This item's original statement that "'Lucy' and her ilk strongly indicate that humans are descended from apes" is not consistent with current understanding of human evolution -- that modern humans and apes evolved from a common ancestor. As anthropologist Eric Delson wrote: "Similar fossils are known in Africa that may have been close to the common ancestry of the chimpanzee, gorilla, and humans. Based on both fossils and studies of the genetic structure of living apes and humans, most scientists think that the two African apes split off from the human line around 8 to 10 million years ago." We regret the error. Thanks to reader G.S. for the tip.