Death Rites are One of the Features Common to Every Human Culture

The title is according to E. O. Wilson's On Human Nature, wherein he actually cites it to some other guy. Pretty neat, huh? But this important work was written in the 70s. Had it been able to predict the future as your Authors can, it would have certainly gone further into what will become the sweetest funeral rites of any culture. Namely, the culture consisting of the entire world.

The macro-culture of all of humanity - that is to say, the features shared by every culture - will be transformed by the zombie crisis of the year 2xxx. According to Romero canon, anybody who dies will be reanimated by, uh, radiation. This applies even if they were not attacked by a zombie. It necessarily follows that after quelling the zombie horde and regaining stable footing of civilization, humanity will have to instate new death rites that are swift and entail complete destruction of the body, so that the deceased will not reanimate.

Of course, humanity has their own way of twisting customs past their original functionality. What follows is what this will evolve to after many decades.

• Anybody who finds the deceased (henceforth referred to as the executor, with apologies to Tassadar) must first be sure that the deceased is in fact dead. Any child can tell you that this is a simple matter of examining whether the tongue is sticking out, and whether the eyes are replaced by letters X.
• The executor then pushes the deceased up against a wall or some other sturdy object, while shouting "YOU ARE DEAD!" in a scary voice.
• The executor draws a ceremonial dagger that all people carry. With it, he deeply cuts the throat of the deceased to ensure a severed connection from body to head.
• With the same dagger, the executor carves a large rectangle into the torso of the deceased, effectively disembowling him. The executor proceeds to rip as many organs and guts from this hole as he can in one rough grab, and to dump them upon his own head to experience spiritual bonding with the deceased. There is no greater sign of respect than to show that the dead's entrails are fit to be the finest headwear.

The preceding steps are, as it is plain to see, the very logical conclusion of cultural evolution after the zombie crisis. The strange bit that seems to stray from the functionality is that, in most cultures, it eventually becomes normal for the executor to slit his own throat, eviscerate himself, and dump his organs upon the head of the deceased. Perhaps this reciprocation is to show that the deceased, too, once respected the executor. Nonetheless, it makes encountering a corpse seem much more troubling from our cultural perspective.

Two final notes:

1. Assassins with two targets have a much easier job when this custom is about. They need only wait until the targets are near each other and relatively secluded, and then kill one of them from afar. The custom is so ingrained that the other target would proceed to perform the fatal funeral rites.
2. In order to protect one's loved ones, someone who wishes to commit suicide would likely commit what is considered a "complete suicide" - that is, do so in some manner that results in his own throat already cut and his own viscera already atop his own head. This way, since the executor and the deceased are the same person, both the first part and the reciprocation of the custom have already been carried out, and any discoverer is safe.