Genocides happened before the 20th century, too, and even though there had been no poison gas before WWI, people have always been very creative and employed whatever technical means they had to blow each other up, hack each other to pieces, bombard, burn, cook, maim, slash, squash, flatten the enemy in whatever way possible and available. That the 20th century saw war and genocide on an unprecedented scale was just a function of technological progress ahead of humanitarian progress, I think. But overall, the outcome of all that is a world with improved humanitarian thinking in general, even if we all still have a long way to go.
I also think the insight that it's really not so nice to exploit "underdeveloped" countries is really progress, not descent, although like I said, we actually still do that to a certain degree, if on a less massive scale and maybe less violent, too. I think overall, things are very slowly getting better in general though.
Obviously, this is not the right place to discuss this subject in general or this book in particular, but still, thanks for sharing these insights from the book. I also realize that such complex studies and conclusions can no be reduced to a short post either, and I note that everyone here who has commented on the book has apparently found it worth reading, so I think I may actually pick it up.