Kingdoms of Either and Or

Something really worth taking note of, from Jonathan Weiner's The Beak of the Finch (p. 231-232):

Currently most evolutionists regard the possibility of speciation among neighbors as unorthodox, even though Darwin himself proposed it. The standard model of speciation requires geographic isolation. That has been the canonical pattern for half a century, and many evolutionists belive it is the universal pattern. But evolutionists are forever dividing and subdividing into schismatic sects, kingdoms of Either and Or. Do new species arise in archipelagoes, like Darwin's finches, or do they arise among neighbors? Is the origin of species fast or slow? Is the mechanism natural selection or sexual selection? And so on. None of these questions really have ot be framed either-or. It is almost a law of science: the more indirect the evidence, the more polarized the debate. Evolutionists sometimes catch themselves sounding like the Little-Endians and Big-Endians in Gulliver's Travels, fighting tooth and nail over the proper way to crack an egg. Meanwhile, the more direct the evidence, the less the answers look either-or.

This 'law' of indirect - or poor - evidence resulting in more polarized debates seems to work in other areas of science as well. For example, in sedimentary geology, there is (was?) a strong debate about whether most thick-bedded sands deposited in the deep sea are due to deposition from turbidity currents or debris flows. Probably the only positive outcome of the debate is that some people are paying more attention to the evidence and they are starting to realize exactly that "the more direct the evidence, the less the answers look either-or". Debris flows can easily become turbulent flows - and the other way around: in their final, depositional stages, turbidity currents can transform into predominantly laminar flows. To claim that 99% of deep-water sands result from debris flows rather than turbidity currents just because many depositional features suggest laminar behaviour is a perfect example of thinking in terms of black-and-white or kingdoms of 'Either and Or'. It is analogous to calling cars 'frictional machines' because they use friction to stop.