Abstract: Tau lesions (pretangles, neuropil threads, neurofibrillary tangles) in select neuronal types are essential to the pathogenesis of Alzheimer’s disease. Pretangle formation marks the beginning of the pathological process and is of particular interest because it is temporally closer to the prevailing conditions that induce the pathological process underlying Alzheimer’s disease in contrast to late-stage disease. However, not all pretangles convert into neurofibrillary tangles. We propose that the development of tau lesions in Alzheimer’s disease is traceable to differences between early- versus late-maturing oligodendrocytes and to the exceptionally protracted myelination of late-developing portions of the human brain. Conclusions drawn from these considerations should encourage development of new preventative and disease-modifying strategies.