PrepTest 150, Section 3, Question 15
Carrillo: Using the number of existing primate species,(63 more words not shown)
The dialogue provides the most(11 more words not shown)
- Aprimates have been(7 more words not shown)
- BCarrillo's statistical model(12 more words not shown)
- Cthe available sample(14 more words not shown)
- Dthe dating of(8 more words not shown)
- Efossils of the(8 more words not shown)
Reading the argument
How good are the model's inputs?
Carrillo uses species counts and genetic diversity to estimate the first primate's appearance at 81.5 million years ago. My first question would be whether the data and the model's use of them are reliable. A calculation is only as persuasive as the support for using it here. But we haven't been given a reason to decide that question yet.
Olson objects that the oldest fossils found date to only 55 million years ago. That doesn't by itself establish that earlier primates didn't exist. Perhaps older remains never became fossils, or perhaps their fossils haven't been discovered. The oldest evidence found isn't automatically evidence of the very first animal.
What we’re looking for
Still, we don't have to settle which estimate is right. Olson calls Carrillo's estimate 'sheer speculation,' while Carrillo says the model strongly supports it. For the disagreement, I'd look for the reliability of this method of dating primate origins. Criticizing the basis for an estimate isn't the same as supplying a different date.
Working the answers
- A
Carrillo's estimate puts primates well before 55 million years ago. Olson doesn't say they definitely appeared no earlier than that. Olson could think primates are older than the known fossils and still reject 81.5 million as an unsupported estimate. We don't have the opposite age claims A requires.
- BCorrect
Carrillo presents the statistical model as strong support for dating the first primate. Olson treats the resulting estimate as speculation. They therefore disagree about whether this model provides a reliable way to establish that date, even though Olson doesn't identify the true date instead.
- C
Carrillo discusses genetic diversity, but doesn't claim that the available fossil sample represents the full variety of primates. Olson identifies the age of the oldest discovered fossils, not whether the sample represents the variety of species. Those aren't opposing positions on representativeness.
- D
Carrillo could accept that the discovered fossils are correctly dated to 55 million years ago while believing that earlier primates existed. The model's earlier estimate doesn't require disputing the age of those particular fossils. We don't have a disagreement about their dating.
- E
Neither speaker establishes that the very first primate species is represented among discovered fossils. Carrillo's model can estimate an origin without claiming that the first species' fossils have been found. Olson's reference to the oldest known fossils doesn't explicitly make that identification either. E asks about a claim their exchange doesn't settle.
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