What is objective fitness?

Recent evidence indicates that humanity has undergone significant evolutionary change over the last 5,000 to 10,000 years. Slate's William Saletan writes that much of this evolution has come about because of cultural factors. For example, because humans learned to domesticate cows, there is an evolutionary advantage (which I lack) to being lactose tolerant.

If humans basically stopped evolving 100,000 years ago then there would be no significant genetic differences among the races. But if humans have undergone significant evolution over the last 5,000 to 10,000 years then their almost certainly are such differences. In a current article in Slate, Saletan is trying to downplay the importance of these differences. He writes:

"Much of what now passes for 'natural selection' isn't exactly natural. It's social. As such, it deserves no presumptive respect as a validator or promulgator of objective fitness."

What does "objective fitness mean"? Natural selection works to favor creatures who are better adapted to their current environment regardless of how much that environment has been influenced by humans.

I think Saletan is defining "objective fitness" as how well a human would survive in the world of, say, 100,000 years ago. But why is this of any possible relevance?

Saletan is trying to be politically correct and come up with a scientific reason why the evolution that probably occurred over the last 10,000 years shouldn't make anyone feel better or worse about their own or their group's genes. There may well be serious reasons for this, but "objective fitness" is not one of them. As scientists learn more about human genes expect more silly but politically correct opinion pieces on genetics.