The assertion that Australopithecus afarensis, Australopithecus africanus, and Paranthropus boisei, three species believed to have existed around 3 million years ago, may actually represent a single species is considered uncertain, as it relies on a singular study published in the journal Nature regarding a specific fossil known as 'fossil A.' An anthropologist anticipates that numerous new studies will bolster this argument in the next year, but even if this expectation is fulfilled, the new studies will not substantiate the claim that the three species are indeed one, since _______________.