Economic growth is faster than population growth or growth in resource consumption.

Hence it's cheaper to “buy back” the effects the longer you wait.

Clark argues that East Asia had higher populations than Europe because of better sanitation. Of course, this meant lower living standards in East Asia too — with fewer people, Europeans had a richer diet and were less likely to die of starvation.

The population is also compounding. I'd like to see your calculation where human effect on environment intersects with technological ability to confront it.

“Some of the physical differences can be also explained by quality of diet.”

Agreed, this is my point. As I wrote in the post:

“So the Sioux were taller than some of the European settlers, because their more violent society was healthier for those who lived.”

Less people to divide available calories between = better diet = healthier society for those who lived.

What are the points of no return?

Certainly they exist for both genetic/cultural divergence and climate change. But you can't say one needs to be focused on rather than the other because of a “point of no return,” because both problems have it as some point.

That is typical Aaron hyperbole, but I guess on a blog where we examine race in genetic constructs and female intelligence by brain volume (neither of which I disagree with, damn science-blind wing of the liberal party) then surely we can say “X 3rd world country folk can die so American captains of industry don't have to take Y% paycuts.”

You seem to be describing a public policy approach to climate change. This was addressed in some depth in Bjorn Lomborg's “Cool It” [1,2]

[1] http://www.amazon.com/Cool-Skeptical-Environmentalists-Global-Warming/dp/0307266923
[2] http://www.tdaxp.com/archive/2007/10/12/review-of-chill-out-the-skeptical-environmentalist-s-guide-t.html