Years before the advent of plate tectonics—the widely accepted theory, developed in the mid-1960s, that holds that the major features
Most geologists and many historians today believe that Wegener's theory was rejected because of its lack of an adequate mechanical basis. Stephen Jay Gould, for example, argues that continental drift theory was rejected because it did not explain how continents could move through an apparently oceanic floor. However, as Anthony Hallam has pointed out, many scientific phenomena, such as the ice ages, have been accepted before they could be fully explained. The most likely cause for the rejection of continental drift—a cause that hasbeen largely ignored because we consider Wegener's theory to have been validated by the theory of plate tectonics—is the nature of the evidence that was put forward to support it. Most of Wegener's evidence consisted of homol0gies—similarities of patterns and forms based on direct observations of rocks in the field, supported by the use of hammers, hand lenses, and field notebooks. In contrast, the data supporting plate tectonics were impressively geophysical—instrumental| determinations of the physical properties of Earth garnered through the use of seismographs, magnetometers, and computers.
The author of the passage discusses the “essential presumptions” (see
A. indicate features of Wegener's theory that caused it to be doubted in its day
B. show why Wegener's theory is now regarded as prescient
C. indicate differences between plate tectonics and the theory of continental drift
D. cite features of the theory of continental drift for which no evidence was available in Wegener’s day
E. point out aspects of Wegener's theory that were accepted well before the advent of plate tectonics
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