Oh okay. What was it about the movie you like more than Rise or Dawn?
I guess I feel more of the world could have been seen though in this take over rather than just the western U.S. I didn't think the movie needed a story that made the humans less intelligent. I thought they would just forget their ways of life and forget how to speak, by the time the original Planet of the Apes takes place. So I thought maybe it was an unnecessary subplot, but maybe it wasn't...
I think the virus mutation was as good an explanation for feral humans as any. Humans have maintained their current level of communication for tens of thousands of years so the odds of them simply forgetting it over the course of 2,000 years (which is how far off the original Apes is) seems a little unlikely even with the threat of sapient apes.
Obviously the virus has polar effects on apes and humans, I still always read the plot of the trilogy as having the virus causing the eventual demise of humans in one way or another.
As it happens, those it can't kill it mutates and causes a kind of reverse-evolution.
The thing to remember though, is not to compare the trilogy to the original movies.
Like, as ironpony said: "I thought they would just forget their ways of life and forget how to speak, by the time the original Planet of the Apes takes place."
The trilogy isn't connected to the original movies at all.
It's simply based on the same book as the other movies.
The original 1963 book though is totally different from all of the different movie versions too.
The explanation in the book is that humans simply tamed and domesticated apes, and over time apes became more sentient, and in turn humans became lazier and lazier to the point they became ape-like.
Eventually apes have a society that directly mirrors what humans had in the 20th century (as seen at the end of Tim Burton's movie).
The story of the original movies, is that humans kill themselves through nuclear war... and over thousands of years, apes and humans simply switch places.
Tim Burton's godawful Marky Mark engine was closer to some things seen in the book, for instance what was seen in that ending, but it was still totally different to the book.
This new version is all about a virus that causes the change.
Humans wiping themselves out by trying to fix themselves, and animal experimentation being the downfall of humans.