The student's text is not strictly plagiarized, but it does closely paraphrase the source material without proper citation. The student has reworded the sentence somewhat, using similar ideas and structure, which indicates reliance on the original source. However, the phrase "life-sized painted bulls and horses" is changed to "ancient paintings," and "overwhelming power" is omitted, which alters the wording but retains the overall meaning.
Plagiarism typically refers to taking someone else's work, ideas, or expressions and passing them off as one's own without appropriate attribution. In this case, the student appears to have taken the core idea from Diamond's work while attempting to modify the language. However, to avoid plagiarism, the student should have either cited Diamond's work directly or provided a proper reference to acknowledge the source of the original ideas.
In summary, while the student text is not a direct quote or a verbatim copy that constitutes plagiarism, it still lacks adequate attribution, making it misleading in terms of originality and giving credit to the original author.