There is no normal...

There is no normal. There is only the majority. Therefore, everything that mankind has deemed normal can, in fact, change within a moment's notice. Before an apocalypse, the normal life included going to work, watching TV and going to stores to buy supplies. Afterwards, the norm would be to simply survive. Whatever is perceived by the majority is what is normal. So basically, human society is based on the subjectivity of our brains.