[E]arth’s climate was not designed for us, hence there is no a priori reason to assume that large negative results due to a few degrees of warming are more likely than large positive ones.

This is from David Friedman’s latest post. The post is a terse, insightful critique of a book on global warming by William Nordhaus and Joseph Boyer.

His commenter Miko wrote:

Quite the opposite, in fact: through the process of evolution, human beings were “designed” for the Earth’s climate. But in the end this still means that your conclusion that a change in climate is as likely to be beneficial as harmful is wrong.

David has a great answer:

Humans were “designed” for earth’s climate over a period for most of which its climate was quite different from the present–we are currently in an interglacial, a relatively short period of warmth in the current long ice age. Hence the evolutionary argument provides no support for your claim.