Historical Science Is Based on Assumptions
The scientific method is limited by that which can be tested, reproduced, and falsified. That which lies outside of these parameters is not science but is in the realm of faith, the un-testable assumptions based on the presumption of naturalism or the revelation of creation.
Science can test an assumption by evaluating the accuracy of the predictions of the different models. That model (theory, belief, revelation) that best predicts that which is observable is the more creditable model of reality. However, since new observations cannot be made, verification is limited.
The assumptions the scientist brings to the study of origins can obscure the evidence. Historical science does not benefit from the repeatable observations that have served as the cauldron of truth for scientific knowledge.