Does an absence of fossil evidence shows that ancestral species did not exist?
Summary of problems with claim:
The fact that a particular species at a given place and time didn't fossilize doesn't mean that the species didn't exist.
Explore Evolution states:
critics argue that Darwin's theory has failed an important test. Just as students are tested by exams, theories are tested by how well they match the evidence. In the overwhelming majority of cases, Common Descent does not match the evidence of the fossil record. A student who gets a correct answer only once in a while does not deserve a passing grade. In the same way, critics say that a scientific theory that only rarely matches the evidence fails the test of experience.Explore Evolution, p. 27
Firstly, taphonomy and earth processes also help us understand why, where, and under what conditions fossils form and explain low abundance (or absence) of fossils in certain situations. Just because paleontologists do not find fossils in certain rocks (or certain preservational environments) does not mean nothing ever lived there. There are many contingencies that explain fossilization, and any 'absence' of fossils is not by default positive evidence against evolutionary theory. There are two different hypotheses/processes at work, taphonomy and evolution, and fossil absence is also very well explained/understood by taphonomic data. Secondly, when fossils are preserved, there is a lot of evidence for common descent. See section on 'transitional fossils' above.