if the asteroid hit tomorrow and modern life as we know it was over?

This was an interesting topic on local radio last night: the host asked for what life skills we might need, individually or as a group, to survive in the post-disaster world without our modern marvels. My top four coincided with what other people suggested, although there were a lot of "silly" suggestions such as the ability to make paper and ink and the ability to make aspirin. Such things would seem of second or third order concerns, but then again it was local talk radio.

My list:

1) ability to make fire
2) ability to hunt, gather, and prepare food (non poisonous)
3) ability to purify water
4) ability to make shelter.

After that, I would hope individuals would recognize their comparative advantages and organize into mutually beneficial trade (after all isn't that what we preach in class). But isn't it more likely that the majority (or all) of the survivors of such a calamity would revert to a zero-sum mentality, at least in the short to medium run?

If this is the case, does that argue for a "retreat" somewhere in the rural hinterlands that you can go to (assuming you could get there) and avoid as much contact with others as possible, at least until the initial zero-sum game is finished? It doesn't sound efficient, but perhaps it would be in a second-best world.