After Thoughts - March 1998

The Classification Problem

This month's feature article discussed the difficulty of classifying animals, and whether or not classification shows an evolutionary path. We should point out that scientists can't even agree on how to classify things as being dead or alive. You may have read the following discussion in this month's issue of National Geographic.

Before [biochemist Gerald] Joyce shows off his experiments, I ask him a question that has been bothering me: "What does it mean to be alive?" Dressed in khaki pants and looking no older than his students, Joyce gets antsy as he tries to respond. "You can't put forward a firm scientific definition of life. It's a term that really only has popular meaning." Although scientists have offered many definitions of life, all fall short at some level. Some are so broad they encompass nonliving entities, such as fire or mineral crystals. Others are so narrow they disqualify mules, which are sterile. Joyce favors the definition of life as "a self-sustained chemical system capable of undergoing Darwinian evolution."1

Joyce favors a definition that requires the theory of evolution to be true. There can be no life without evolution, according to his definition. By definition, evolution can't be questioned. His definition is biased by his belief in evolution.

Similarly, it is difficult to know how to classify species. The usual method is to use sexual viability, but this method fails for asexual creatures and fossils.

The fact that it is even possible to classify species was troublesome to Darwin. If all species gradually evolved from each other, then it should be as hard to divide them as it is to divide the colors in a rainbow.

As Charles Darwin pointed out in On the Origin of Species, the kind of discrete species that ambitious breeders of domesticated animals used as a touchstone was inconsistent with his theory of descent with modification--or, indeed with any evolutionary theory, whether its mechanism was natural selection or not. If species changed slowly but markedly through time--if no precise boundaries separated living forms from their extinct forebears--then the lines between similar living species correspondingly paled in significance.2

In other words, the classification problem should be even harder than it is, if evolution is true. There should be so many creatures gradually evolving into other creatures that it is impossible to distinguish them.

But the problem we actually find is that there are so many distinctly different creatures that don't fit neatly in any classification system. The platypus, bat, whale, and kangaroo don't really fit in any category. There isn't a gradual blending of features or any clear signs of evolution. One either has to imagine all sorts of unknown transitional types if evolution is true, or admit that the physical world is inconsistent with the theory.

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1 Richard Monastersky, National Geographic "The Rise of Life on Earth" March 1998 page 69 (Ev)
2 Ritvo, The Platypus and the Mermaid and Other Figments of the Classifying Imagination, page 85