Archaeologist: Recently excavated cave layers dated to 40,000 years ago contain stone blades with intricate, symmetrical fluting. Such craftsmanship indicates that the toolmakers had already mastered fluting long before those blades were left in the cave. But modern dating shows humans first entered this region only 43,000 years ago, so fluting technology must have developed within a mere few millennia of the first arrival. Therefore, advanced lithic techniques can emerge very rapidly after a population colonizes a new environment.
Which one of the following most accurately describes the role played in the archaeologist's argument by the claim that the fluted blades' makers had already mastered fluting long before the blades were deposited?
