Hi yrresnik!
I'll try to address all your concerns with this question and identifying author's tone questions in general. Just to be clear, "implicit" just means that something has been implied, but not expressly stated. So you are correct that the author does not
explicitly state that he agrees with the anthropologists in the 3rd paragraph, but his acceptance of them is implied because he provides their evidence without any hint of disagreement, skepticism, hesitancy, etc. (which is also a good reason to eliminate answer choices (B), (C), (D), and (E)!).
Furthermore, it isn't inconsequential that the author counters the view presented by the anthropologists in the 1st paragraph, but does not offer any criticism of the view of the anthropologists in the 3rd paragraph. This is actually a fairly common argument presentation technique that LSAT authors use, both in Reading Comprehension and in Logical Reasoning. In LR, you've probably seen it in arguments which start with some version of "Some people say..." and then the author goes on to argue against whatever "some people say." In RC, it can work in a similar way, as it does here if we focus on the structure of this passage. The 1st paragraph introduces us to the viewpoint of "some anthropologists," the 2nd paragraph presents evidence which calls into question the viewpoint in the 1st paragraph, and the 3rd paragraph presents the viewpoint of "many anthropologists" which accounts for that 2nd paragraph problem in the theory of the 1st paragraph anthropologists. When you think about the structure of the passage as a whole (which is important when considering author's viewpoint!), you see that the author presents one view, finds a problem with it, and then presents another view which solves that problem. That's pretty strong evidence that the author implicitly accepts the view of the 3rd paragraph anthropologists. Their view doesn't have the same problem that he identified in the view of the 1st paragraph anthropologists and he has not presented any problems with their view.
I'm not totally sure what you mean by the tone being subjective if we're determining it relative to the author's tone toward the 1st paragraph anthropologists. As I hope I clarified in my structure analysis, it's not just comparing his view toward the 3rd paragraph anthropologists to the 1st paragraph anthropologists
it's the whole structure of the argument that we're taking into account. And in a certain sense, RC is never going to be quite as mathematical as the Logic Games. We'll always have to settle for the best answer out of the 5 that we've been given; we're always looking for the answer choice that "most accurately describes the author's position." Sometimes this can feel a little subjective. But that's why we have tools for recognizing incorrect answers (sometimes getting rid of them is easier than finding the correct answer) and for analyzing key passage components (focusing on those VIEWSTAMP elements helps us stay on track those big picture elements which don't often come from just a sentence or 2).
Identifying an author's tone can be tricky! You often need to take into account the passage as a whole (including structure, author's viewpoint, main point, etc.). So a Combination Answer in a question like this doesn't come from directly adding 2 statements together; it comes from adding the whole passage together. That's why tone is a component of VIEWSTAMP. It may help to review the section on tone in the earlier VIEWSTAMP chapter as it really can be a tricky concept to master.
Hope this helps!
Best,
Kelsey