Because 4-dimensional CP is a good symmetry of many higher-dimensional theories, this suggests the possible existence of a universal CP-violating phase originating from the process of compactification. Such a phase, if it existed, would not be easy to uncover since the phases in Yukawa matrices are not simply related to the observed CKM phase. Hierarchical Yukawa models, of the type arising in F-theory GUT models provide an interesting exception. I discuss specifically an F- theory GUT model studied by Heckman and Vafa with hierarchical Yukawa matrices with complex phases of O(1), which they showed leads to a CKM phase of O(1). A more detailed examination of the model, although confirming their results, is seen to be also compatible with having a phase do= p/3 imprinted on the Hermitian Yukawa matrices, leading to sin dCKM» sin do