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 doesnt 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.
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.
