I think that the original Dawn of the Dead is the best zombie movie ever made.. Stephen and Peter were just speculating why they would be coming to the mall.. For all we know, they were very basic memories that there were people there, aka food...
Day of the Dead didnt really show us anything new, because in Dawn, they did show the dead holding a phone receiver up, trying to work a cash register, a zombie with an interest with guns, etc, so Bub was just another that was chained to a wall with objects placed in front of him, and was rewared with food
In Land of the Dead, they were walking around doing daily tasks that contradicted the fact that they needed to feed on the humans.. Then out of nowhere, there was a uniformed leadership and more advanced communication skills between the dead..
I would like to think that the evolution from mindless zombies, to more sophisticated ones would take too long and the bodies would just rot away before it had a chance, unless in colder climates..
I have not seen Diary of the Dead, and only watched Survival cause it was on Netflix and wanted to see just how bad it was