The student's text is not technically plagiarized, as it does not reproduce the source verbatim and does express the core idea in different wording. However, it closely mirrors the structure and meaning of the source material without adequate attribution or original analysis. The phrase "as modern in their minds as they were in their skeletons" is directly carried over from the source, albeit rephrased slightly.
Plagiarism is generally defined as using someone else’s ideas or expressions without proper acknowledgment. In this case, while the student text paraphrases the main concept, it lacks citation of the original author. To avoid plagiarism and appropriately give credit to Jared Diamond, the student should either provide a citation or quotation marks if they are quoting directly, along with a reference to the source.
In summary, the student text shows a good understanding of the idea but falls short in academic integrity due to lack of attribution to the original source.