Replying to Reviewer 1
The Introduction is still too long. In fact, it's just as long as it was in the first version. Maybe the authors think I will forget this point if they just ignore it.
The Introduction is still an exercise in "putting the cart before the horse." The authors try to explain their findings before they actually present them. Such an approach would be defendable if the same findings had appeared in a previous study. But there is no such previous study, certainly not the massive work by Edward Gibbon. He never claimed that mean cognitive ability had declined during Rome's Imperial period.
I would be more forgiving if the authors could write clearly and succinctly. Unfortunately, that doesn't seem to be the case. I'm still having trouble understanding their argument, since it branches off in several directions. Here is my understanding of what they mean to say:
1. During pre-Imperial times, the Romans had "high intelligence and other pro-social psychological traits." The authors seem to be arguing that pro-sociality creates an orderly environment that is conducive to pursuits with high cognitive demands (cf. Gregory Clark).
2. The establishment of the Empire led to a decline in pro-sociality. Life became too good. There was "clean water, basic medical care and an abundance of food" (Oh really?). There was also immigration from the Greek-speaking eastern provinces. All of these trends presumably caused a decline in mean cognitive ability. I say "presumably" because the authors provide no evidence that the Greek-speaking East was less intelligent on average than the Latin-speaking West. The stereotype of the time was the reverse: the East was the home of thinkers and philosophers. In any case, the authors should not assume what they wish to prove.
3. Meanwhile, there was climate warming. Perhaps this was a factor in Rome's decline, or perhaps not. The authors are like the hunter who tries to catch two rabbits at the same time.
4. With the decline of the Empire, the Roman population may have entered "another eugenic phase where intelligence is rising." I initially saw this as a reference to Christianity and selection for pro-sociality (cf. Schulz et al.), but apparently I was mistaken.
I'm coming around to the other reviewer's (harsh) judgment. The results are interesting. Unfortunately, they are sandwiched between a lot of intellectual musing and meandering.
Thank you for your feedback and suggestions. I have taken your comments into consideration and made the necessary revisions to address the issues raised. I have extensively re-written the introduction to make it clearer, and I have removed the speculative parts of the introduction, including the reference to the Cold Winters theory and the assumption about immigration from the Eastern Mediterranean causing a decrease in polygenic scores. I agree with your point that there is no evidence to suggest that the Greek-speaking East was less intelligent on average than the Latin-speaking West.
Furthermore, I have removed the paragraphs describing the ancestry shifts from the introduction, as you recommended. However, I respectfully disagree with your statement that "The Introduction is still an exercise in 'putting the cart before the horse.'" In fact, the hypothesis that there was a cognitive decline in classical antiquity has been proposed before and is not merely a post-hoc interpretation, as you suggested.
Additionally, you mentioned that there is no previous study with similar findings to support our approach. While it is true that the findings presented in this paper are novel, the hypothesis itself is not. Peter Frost, in a blog post published around the same time our paper was submitted, discussed the decline in mean cognitive ability during Classical Antiquity and proposed potential causes based on historical phenomena discussed by other authors.
To support this, I have included a reference to Peter Frost's blog post in the introduction, where he discusses the decline in cognitive ability and suggests three main causes. This demonstrates that the hypothesis of a cognitive decline in the Mediterranean has been previously advanced by Woodley of Menie et al. (2019) and Peter Frost in 2022.
Thank you once again for your valuable feedback, which has helped improve the clarity and accuracy of the introduction.
