At a February 12, 2002, news briefing, Secretary of Defense Donald Rumsfeld explained the limitations of intelligence reports: "There are known knowns. There are things we know we know. We also know there are known unknowns. That is to say, we know there are some things we do not know. But there are also unknown unknowns, the ones we don't know we don't know."

Rumsfeld's logic may be tongue-twisting, but his epistemology was sound enough that he was quoted twice at the World Summit on Evolution. The June conference, hosted by San Francisco University of Quito, was held on the Galpagos island of San Cristbal, where Charles Darwin began his explorations. Rumsfeld's wisdom was first invoked by University of California at Los Angeles paleobiologist William Schopf, who, in a commentary on a lecture on the origins of life, asked: "What do we know? What are the unsolved problems? What have we failed to consider?"

Disputation is at the heart of a robust science

Creationists and outsiders often mistake the last two categories for signs that evolution is in trouble or that contentious debate between what we know and do not know means that the theory is false. Wrong. The summit revealed a scientific discipline rich in data and theory as well as controversy and disputation over the known and unknown.

For example, Schopf began with the known: "We know the overall sequence of life's origin, from CHONSP [carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus], to monomers, to polymers, to cells; we know that the origin of life was early, microbial and unicellular; and we know that an RNA world preceded today's DNA-protein world. We do not know the precise environments of the early earth in which these events occurred; we do not know the exact chemistry of some of the important chemical reactions that led to life; and we do not have any knowledge of life in a pre-RNA world." As for what we have failed to consider, Schopf noted a problem with what he called "the pull of the present"--it is extremely difficult to model the early earth's atmosphere and the biochemistry of early life because we are so accustomed to conditions today.

Rumsfeld's heuristic was summoned again at the end of the conference by University of Georgia evolutionary biologist Patricia Gowaty, in response to Stanford University biologist Joan Roughgarden, who declared that Darwin's theory of sexual selection is wrong in its claim that females choose mates who are the most attractive. "People are surprised to learn how much sex animals have for purely social reasons and how many species have sex-role reversal in which the males are drab and the females are colorfully ornamented and compete for the attention of males," Roughgarden said. Gowaty agreed that exceptions to Darwin's theory exist and that there are many unknowns. But, she added, since Darwin much has been learned about mate selection and competition.

Between these Rumsfeldian bookends, scientific skepticism was rampant. University of Massachusetts Amherst biologist Lynn Margulis said that "neo-Darwinism is dead," because "random changes in DNA alone do not lead to speciation. Symbiogenesis--the appearance of new behaviors, tissues, organs, organ systems, physiologies or species as a result of symbiont interaction--is the major source of evolutionary novelty in eukaryotes: animals, plants and fungi." University of California at Berkeley paleoanthropologist Timothy White suggested that his colleagues have engaged in far too much species splitting in classifying fossil hominids. American Museum of Natural History paleontologist Niles Eldredge explained how punctuated equilibrium--the idea that long periods of species stability are punctuated by rapid bursts of speciation--better accounts for the fossil record than the theory of slow and steady gradualism.

During the conference, I had a nightmarish thought: creationists could have a field day yanking quotes out of context while listening to a room full of evolutionary biologists arguing over specific issues. In point of fact, such debates are all within evolutionary theory, not between evolutionary theory and something else. And this boundary between the known and the unknown is where science flourishes.