Could it be possible that some zombies are smart or just partially zombies so that they are still able to develop tool like in the S1E2 of The Walking Dead where we can see a walker (zombie) use a rock trying to break a glass of a door?
The evolution of zombies in The Walking Dead goes more like this:
- Though the show has been on the air since 2010, only about two years have transpired in the zombie apocalypse, according to executive producer and make-up supervisor Greg Nicotero
- In season one, we're introduced to the zombie apocalypse about four to five weeks after it has begun.Clothes are pretty much intact, and from far away, most zombies could pass for regular people.
When season three premiered in late 2012, zombies began to look noticeably more gaunt. Eyes began to look even more sunken into faces. There was a focus on walkers looking more rotted and decayed.By the end of season three, there was further discoloration and deterioration to the skin.
Moving into season four, zombies began to decompose even more. At the start of the season, fans have estimated we're approximately 321 days into the zombie apocalypse. Skin has sagged and dried out. Hair begins to diminish. We also saw our first completely charred walker.
Walkers are more prone to falling apart and looking decrepit in season five. It's more common to see noses missing. Clothes are tattered and disintegrating. Bodies, especially those exposed to water, are appearing more skeletal in structure. By the second half of season five, walkers are not looking human anymore. They're becoming mere skin and bone — or close to just bone.
Now, on season six Nicotero told Tech Insider walkers will have more moss and branches growing on them in addition to skin sloughing off.
Based on this declarations of Greg Nicotero I could say that zombies in season 1 have also more stamina and willing to do more things. In the first epidose of season 1 they can move a tank whereas on season 7 a simple wire makes them stop.
In a sense is not only the flesh what is deteriorating but somehow the "brain" of the zombie.
The most common and believable explanation is that all new Zombies show the same intelligence because they retain some of the intelligence that they had as humans. This explains why almost all of the zombies in the first season are fast because most are newly turned. You can see the same behavior in the newly turned Merle. As time progresses they will get slower and dumber. Although Kirkman has said they do not rot. Their cell structure is not replenished as it would be if they were alive.