Yesterday was the 200th anniversary of Charles Darwin's birth, and the mainstream media was filled with the obligatory slew of evolutionary pieces. Read one article claiming that religious people tend to have more children than 'free-thinking' folk, and so (since most people stick with the religion they're born into) in a hundred years religious zealots will make up an overwhelming majority of the global population. Good luck future generations!
This got me thinking about what selective pressures may currently be at work on humans. In the developed world, modern man lives free of want and can successfuly combat infectious disease. In short, we are guaranteed survival - at least till reproductive age, which is all that matters for evolutionary purposes. The welfare state, as Richard Dawkins pointed out, is not a Darwinian arena. So is anything being selected for? What traits would proliferate in such an environment?
How about genes that modulate one's temperament [Such genes do exist; check out this article on a variant associated with optimism: http://www.economist.com/science/displaystory.cfm?story_id=13176767] An increasingly unchallenging lifestyle has given us so much idle time that perhaps even a slightly morose disposition can sink a mind into a deep depression. In their despair, these people may not live long enough to reproduce, or they may decide against bringing another life into such a miserable world. Perhaps, then, variation that promotes a sense of joie de vivre might proliferate in the human population. Positive selection for genes that encode happiness!
Now, one could argue that variants that make humans suicidal would be eliminated regardless of the environment, and such selection would have been happening since the origin of our species. That may be true; all I'm saying is that our modern lifestyle may amplify the effects of depression. Someone struggling to survive while living a hunter-gatherer existence does not have the time to ponder, get disillusioned and depressed; whereas in Bruges, time is by no means in short supply!
An important caveat is that I've neglected the impact of antidepressant drugs, which would counter negative selection against depression. Although, if the drugs really are effective, our species will find happiness one way or another - via natural selection or human intervention!
