#19 - Anthropologist: It was formerly believed that

[Emily Haney-Caron]

Hi rneumann,

Close! I think you just got two of the terms mixed around; prehistoric humans are ancestors of contemporary humans, not the other way around. Otherwise, though, you've got it! Now the challenge is to trust your instincts when you think you've reasoned it through on your own.

[Bahar]

I got the point that I need to find an answer to show that she was intentionally did that to be guilty but I refute AC E when I was reasoning she didn't talk to experts that means that she didn't know. Means she was naive or just did a mistake , I didn't get it in a way that she intentionally did it and she was biased!!!
Why this interpretation is wrong?

[Adam Tyson]

Hey there Bahar, I think you are looking in the wrong thread here. This question from June 2011 has to do with an assumption regarding the DNA of humans and Neanderthals. There's nothing about guilt or mistakes here. Please take a look at which test and section your question is in, and find the thread that matches. When you do, you can check the explanation in the correct thread and, if that isn't satisfactory, re-post your question there. Thanks!

[frk215]

Hello! I would like to make sure my reasoning for why c, when negated, would hurt the argument.

So my negated version of c is just: The DNA of prehistoric Homo sapiens ancestors of contemporary humans was significantly more similar to that of Neanderthals than is the DNA of contemporary humans.

We know that the prehistoric homo sapiens were ancestors of contemporary humans. If we believe that these homo sapiens were more similar to that of neanderthals than modern humans (in terms of DNA) and we know that the homo sapiens were definitely related to humans, then the DNA similarity doesn't mean anything.

This would then hurt the argument because the driving force behind the conclusion is the premise that the neanderthal dna is different (i.e. if the DNA is different, neanderthals weren't ancestors). Our negated assumption would directly attack this driving force.

How'd I do?

[katehos]

Hi frk215,

Nailed it! Great job employing the Assumption Negation Technique.

Best,
Kate

[otter1234]

Hi, Powerscore,

I don't understand why (C) is a necessary assumption. I understand that if prehistoric Homo sapiens were more similar to Neanderthals than contemporary humans are, this similarity might suggest that the lack of DNA similarity in modern humans doesn’t necessarily rule out interbreeding in the past. This would imply that the significant difference between contemporary humans and Neanderthals might not be conclusive evidence against interbreeding.

Given this, could it still be possible that Homo sapiens interbred with other species? For example, if Homo sapiens interbred with another species that contributed to their genetic divergence from Neanderthals, this could explain why contemporary humans have significant DNA differences from Neanderthals, despite prehistoric Homo sapiens and Neanderthals initially being more similar. I am not quite comfortable to eliminate this kind of alternative explanation.

Please excuse any mistakes in my English, as I am an international student. I would appreciate it if you could let me know if there are any issues with my logic. Thanks!

[Adam Tyson]

The reason answer C is a necessary assumption is because the author is basing their argument on the difference in DNA. The author thinks that if our DNA is very different from Neanderthals, then our ancestors, who presumably also had DNA very different from Neanderthals, could not have bred with them. Dogs can't interbreed with cats, cows can't interbreed with horses, etc. The two groups are too different in their underlying genetic makeup.

But if Homa sapiens DNA was much more similar to Neanderthal DNA than ours is, then maybe they could have interbred? If that's true, then we cannot rely on information about our DNA to come to the anthropologist's conclusion. Our DNA is not as relevant as they think; we should instead be looking at Homo sapiens DNA. This is a big problem with the argument, and so the author must have assumed that it was not true.

Assumptions will often fix problems in the argument. We call these "defenders," because they defend the argument against possible attacks. But while this answer does defend the argument against that particular attack, it doesn't prove the conclusion. This isn't a sufficient assumption, aka Justify the Conclusion, but a Necessary Assumption. I think, from your analysis, that you may have been approaching this question with the idea that the correct answer had to prove the conclusion, when it's really the other way around. The argument requires the answer to be true, but the answer doesn't have to guarantee the truth of the conclusion.