Biologist, Philosopher Discuss How to Make the Case for Evolution Even Stronger

A biologist and a philosopher speaking at a recent AAAS lecture offered compelling views on how to defend evolution against advocates of creationism and Intelligent Design: Teach people the scientific evidence, said the biologist. And don’t be afraid to take on evolution opponents in the schools, said the philosopher.

According to Sara Via, professor of biology and entomology at the University of Maryland, our understanding of speciation has come a long way since the publication of Charles Darwin’s The Origin of Species. Speciation is an area of contention for many anti-evolution advocates. She began by highlighting the work of two eminent biologists, Ernst Mayr and Theodosius Dobzhansky.

Mayr argued that geographic barriers are a critical factor in the evolution of reproductive isolation, the cause of speciation. Dobzhansky advanced Mayr’s ideas by hypothesizing that genetic incompatibilities accumulate during geographic separation, and that these are the predominant mechanism of reproductive isolation.

But Via pointed out that this evolutionary view of speciation is only partially complete.

“Beginning with Mayr and Dobszhansky, evolutionary biologists looked into the distant past to figure out present-day species became reproductively isolated,” Via said. “There is nothing harder to do than to explain the past 1 million, 2 million, 3 million years ago." According to Via, who spoke at a 20 April lecture in Washington, D.C. organized by the AAAS Dialogue on Science, Ethics and Religion (DoSER), recent approaches to speciation focus on natural section, i.e. how divergent selection for use of different resources, or habitats may drive speciation. Via finds this view, called ecological speciation, a promising means of studying speciation in action.

By focusing on how natural selection leads to speciation, Via argues that religious arguments against speciation become moot. Anti-evolutionists often contend that micro-evolution (changes within a species) is different from macro-evolution (change from one species to another). Many creationists believe that evolution can occur within the "kinds" of organisms said to have been created. But they do not believe that new "kinds" can be evolved.

Via illustrated that the idea of “kinds” has little scientific basis, because gradations between many forms that one might classify as different "kinds" were more or less continuous over evolutionary time. As one example, she showed a figure that included pictures of all of the intermediate species between the evolution of humans and chimpanzees from their common ancestor and demonstrated convincingly that there is no obvious place to draw a line between “kinds.” She concluded that there is no scientific reason to doubt that the same mechanisms that lead to microevolution and adaptation also drive speciation.

Via said that, in the absence of actual scientific knowledge, people’s understanding of evolution is often limited to what they can imagine.

“How do you evolve a salamander from a trout?” she quipped. “This is the way non-scientists often think about vertebrate evolution—in terms of present-day species with which they are familiar. Given this orientation, it’s pretty hard to imagine how such a big change could occur.”

If people had a better understanding of how natural selection works and how new phenotypic variation arises, and more familiarity with the many underlying similarities between seemingly very different organisms, they might have less trouble imagining how many speciation events may have occurred, she said.

Emmett Holman, associate professor of philosophy at George Mason University, also remarked on the need to address the fact that while many creationists allow for microevolution within species (whether bacterial immunity or dog breeds), they do not see how the same mechanism could lead to new species or to the large differences seen between current organisms.

Holman, the discussion’s respondent, finds many of the creationist’s criticisms naïve; still, he acknowledged that some raise a number of debatable questions. He contends that the best way to debunk creationism would be to offer a non-required philosophy of science course in the public high schools and treat Intelligent Design at a foil to evolution.

Addressing the resistance teaching such a course has received from scientists and science educators, Holman said, “Why do scientists act like they have something to hide? Perhaps in the short-term [teaching I.D.] would increase [its] credibility, but the more biology you learn, the less compelling the objections to evolution are . . . the less convincing they seem.”

Holman contends the scientific community’s reluctance to discuss I.D. is clearly part of a broader trend to avoid suggesting that science and religion are by definition in conflict.

“This is a complicated issue about which thoughtful scientists disagree,” Holman said. “I side with those who think there is, in some respects, an unavoidable conflict.”

AAAS established DoSER in 1995 to facilitate communication between scientific and religious communities. DoSER builds on AAAS’s long-standing commitment to relate scientific knowledge and technological development to the purposes and concerns of a society at large. The objectives of the program are to contribute to the level of scientific understanding in religious communities and to promote multidisciplinary education and scholarship of the ethical and religious implications of advancements in science and technology.

Benjamin Somers

28 April 2006