If evolution happened, the fossil record should show continuous and gradual changes from the bottom to the top layers. Actually, many gaps or discontinuities appear throughout the fossil record (a).
a. “But, as by this theory innumerable transitional forms must have existed, why do we not find them imbedded in countless numbers in the crust of the earth?” Darwin, The Origin of Species, p. 163.
“...the number of intermediate varieties, which have formerly existed [must] truly be enormous. Why then is not every geological formation and every stratum full of such intermediate links? Geology assuredly does not reveal any such finely-graduated organic chain; and this, perhaps, is the most obvious and serious objection which can be urged against the theory [of evolution].” Ibid., p. 323.
Darwin then explained that he thought that these gaps existed because of the “imperfection of the geologic record.” Early Darwinians expected the gaps would be filled as fossil exploration continued. Most paleontologists now agree that this expectation has not been fulfilled.