Dispatches from the Creation Wars

Plant People are People Too

When we talk about evolution, we almost always talk about animals or microbes, with only a rare mention of plants. The reality, though, is that evolution is a powerful theory in explaining the natural history of flora as well as fauna. The study of plants is called botany. Last summer, the Botanical Society of America released a statement about the importance and validity of evolution that is a must-read for anyone who wishes to understand this issue. One of the great things about this statement is that it emphasizes the usefulness of evolutionary theory, the fact that plant biologists use the theory not only to explain the origin of floral variety, but to solve a variety of problems in the field. It says:

The fairness argument implies that creationism is a scientifically valid alternative to evolution, and that is not true. Science is not about fairness, and all explanations are not equal. Some scientific explanations are highly speculative with little in the way of supporting evidence, and they will stand or fall based upon rigorous testing. The history of science is littered with discarded explanations, e.g., inheritance of acquired characters, but these weren’t discarded because of public opinion or general popularity; each one earned that distinction by being scientifically falsified. Scientists may jump on a “band wagon” for some new explanation, particularly if it has tremendous explanatory power, something that makes sense out of previously unexplained phenomena. But for an explanation to become a mainstream component of a theory, it must be tested and found useful in doing science.

To make progress, to learn more about botanical organisms, hypotheses, the subcomponents of theories, are tested by attempting to falsify logically derived predictions. This is why scientists use and teach evolution; evolution offers testable explanations of observed biological phenomena. Evolution continues to be of paramount usefulness, and so, based on simple pragmatism, scientists use this theory to improve our understanding of the biology of organisms. Over and over again, evolutionary theory has generated predictions that have proven to be true. Any hypothesis that doesn’t prove true is discarded in favor of a new one, and so the component hypotheses of evolutionary theory change as knowledge and understanding grow. Phylogenetic hypotheses, patterns of ancestral relatedness, based on one set of data, for example, base sequences in DNA, are generated, and when the results make logical sense out of formerly disparate observations, confidence in the truth of the hypothesis increases. The theory of evolution so permeates botany that frequently it is not mentioned explicitly, but the overwhelming majority of published studies are based upon evolutionary hypotheses, each of which constitutes a test of an hypothesis. Evolution has been very successful as a scientific explanation because it has been useful in advancing our understanding of organisms and applying that knowledge to the solution of many human problems, e.g., host-pathogen interactions, origin of crop plants, herbicide resistance, disease susceptibility of crops, and invasive plants.

This is a very important thing to keep in mind, both the premise that explanations in science must be testable and falsifiable, and the conclusion that evolutionary theory is successful because it is used every day to solve problems. They go on to give a very good example, and to point out the disparity between the usefulness of evolution and the allegedly competing theories of creationism and ID:

For example, plant biologists have long been interested in the origins of crop plants. Wheat is an ancient crop of the Middle East. Three species exist both as wild and domesticated wheats, einkorn, emmer, and breadwheat. Archeological studies have demonstrated that einkorn is the most ancient and breadwheat appeared most recently. To plant biologists this suggested that somehow einkorn gave rise to emmer, and emmer gave rise to breadwheat (an hypothesis). Further evidence was obtained from chromosome numbers that showed einkorn with 14, emmer with 28, and breadwheat with 42. Further, the chromosomes in einkorn consisted of two sets of 7 chromosomes, designated AA. Emmer had 14 chromosomes similar in shape and size, but 14 more, so they were designated AABB. Breadwheat had chromosomes similar to emmer, but 14 more, so they were designated AABBCC. To plant biologists familiar with mechanisms of speciation, these data, the chromosome numbers and sets, suggested that the emmer and breadwheat species arose via hybridization and polyploidy (an hypothesis). The Middle Eastern flora was studied to find native grasses with a chromosome number of 14, and several goatgrasses were discovered that could be the predicted parents, the sources of the BB and CC chromosomes. To test these hypotheses, plant biologists crossed einkorn and emmer wheats with goatgrasses, which produced sterile hybrids. These were treated to produce a spontaneous doubling of the chromosome number, and as predicted, the correct crosses artificially produced both the emmer and breadwheat species. No one saw the evolution of these wheat species, but logical predictions about what happened were tested by recreating likely circumstances. Grasses are wind-pollinated, so cross-pollination between wild and cultivated grasses happens all the time. Frosts and other natural events are known to cause a doubling of chromosomes. And the hypothesized sequence of speciation matches their observed appearance in the archeological record. Farmers would notice and keep new wheats, and the chromosome doubling and hybrid vigor made both emmer and breadwheat larger, more vigorous wheats. Lastly, a genetic change in breadwheat from the wild goatgrass chromosomes allowed for the chaff to be removed from the grain without heating, so glutin was not denatured, and a sourdough (yeast infected) culture of the sticky breadwheat flour would inflate (rise) from the trapped carbon dioxide.

The actual work was done by many plant biologists over many years, little by little, gathering data and testing ideas, until these evolutionary events were understood as generally described above. The hypothesized speciation events were actually recreated, an accomplishment that allows plant biologists to breed new varieties of emmer and bread wheats. Using this speciation mechanism, plant biologists hybridized wheat and rye, producing a new, vigorous, high protein cereal grain, Triticale.

What would the creationist paradigm have done? No telling. Perhaps nothing, because observing three wheat species specially created to feed humans would not have generated any questions that needed answering. No predictions are made, so there is no reason or direction for seeking further knowledge. This demonstrates the scientific uselessness of creationism. While creationism explains everything, it offers no understanding beyond, “that’s the way it was created.” No testable predictions can be derived from the creationist explanation. Creationism has not made a single contribution to agriculture, medicine, conservation, forestry, pathology, or any other applied area of biology. Creationism has yielded no classifications, no biogeographies, no underlying mechanisms, no unifying concepts with which to study organisms or life.

Thanks to Paul Myers for the heads up on this one.