Self-study
Anthropologist: It was formerly believed that prehistoric . ████ ███████ █████████ ██ ████████████ ██████ █████████ ████ █████████████ ███ ███ ███████ ██ █ █████████████ ███████ █████████ ████ ████ ██ ███ ███ █████ ███ ███ ██ ████████████ ██████ ██ █████████████ █████████ ████ ████ ██ ███ ████████████
Summary
The author concludes that our ancestors didn’t interbreed with Neanderthals. Why? Modern human DNA is very different from Neanderthal DNA.
Notable Assumptions
The author makes several key assumptions:
(1) Modern human DNA is similar to that of our ancestors. The only evidence supporting the author’s conclusion is that modern DNA is very different from that of Neanderthals, so if modern DNA is also very different from our ancestors, the argument makes no sense.
(2) The DNA tests are reliable, and accurate conclusions can be drawn from them.
(3) Genetic similarities between human ancestors and Neanderthals are an indication of interbreeding. Even if we assume points 1 and 2, we still don’t know if that proves the author’s conclusion.
19.
Which one of the following ██ ██ ██████████ ████████ ██ ███ ████████████████ █████████
a
At least some ████████████ █████ ██ ███ ████ ████ ███ ██ ███ ████ ██████ ██ ███████████ ████ ███████ █████████ ██ ████████████ ███████
(A) lends support to the idea that our ancestors did interbreed with Neandaerthals, not that they didn’t. Answer choices that weaken our argument are never necessary, so (A) is not our answer.
b
DNA testing of ███████ ██ █████████████ ████ ████████ ████ ███ ███████ ██ ███████ ████ ██████ ████████
(B) weakens our argument by suggesting the DNA tests might be unreliable. If we can’t trust the accuracy of the tests, how could we draw accurate conclusions based on their results?
c
The DNA of ███████████ ████ ███████ █████████ ██ ████████████ ██████ ███ ███ █████████████ ████ ███████ ██ ████ ██ ████████████ ████ ██ ███ ███ ██ ████████████ ███████
If (C) is not true—if modern human DNA is very different from that of both Neanderthals and our ancestors—then the argument falls apart. The author’s only evidence is that modern DNA is different from that of Neanderthals, so if it’s different from our ancestors’ DNA as well, the tests provide no evidence they didn’t interbreed.
d
Neanderthals and prehistoric ████ ███████ █████████ ██ ████████████ ██████ ████ ██████████ ████████ ████ ████ █████ ███████████████
(D) strengthens our argument, but it’s too strong to be necessary. Even if we negate (D) to say that our ancestors and Neanderthals lived in the same locations, it’s still possible they didn’t interbreed for other reasons.
e
Any similarity in ███ ███ ██ ███ ███████ ████ ██ ███ ██████ ██ ██████████████
(E) plays on the assumption that genetic similarities can be a sign of interbreeding, but it is too strong to be necessary. We only need to know that genetic similarities between humans and Neanderthals point to interbreeding, not that all genetic similarities between all species do. If (E) were true, a 1% similarity in DNA between humans and trees would indicate interbreeding, which is not at all necessary for the argument.