If I understand correctly, your argument is that moral evolution is determined by specific environmental factors, and these factors can be generalized into some simple, linear rules by clear evidence as in natural science.

As I mentioned above, I'm afraid almost half of the book, the Essays on Longtermism, stands on the opposite side of this idea. Evidence discussed in this book seems suggesting that moral evolution is a dynamic process, not simply determined by specific environmental factors. Plus, although we may find some simple rules that are able to explain moral evolution, they are rarely possible to be as simple as linear progressivism. 

I do agree with you that we need to avoid short-sightedness, only that we need to do this very carefully, reducing our long-term goals as little as possible. Therefore, we can focus our energy on those few but really imporatant goals more effectively. Hope this clarify my opinion.

Thank you for your reply. Maybe we understand the term 'evolution' not entirely in the same way. It seems that you take it as a similar term to progressivism, regarding that modern morals are definitely better than those brutal ones in ancient times. Although I agree with modern values as most modern people do, what I argue is that we need to be very caustious when considering 'promoting' those values. 

Put simply, the reason is that moral values survive because they fit the current environment, but the environment may change at any time, anywhere. While we instinctly want to implement our own morals, we must be aware that the same morals may not survive in dissimilar environments. Meanwhile, we also have to adapt ourselves to new changes that are significant enough. So it is not easy to find a fixed moral system to promote.

However, it doesn't mean that we can do nothing. My proposal here is that if we lower our expectation, no longer pursuing something universally long-termly good, we may find it eaiser to practice something locally, mid-termly good. This may be a better strategy for us to finally achieve long-term goodness.