> I there an experiment that can prove that this theory is wrong? I this theory falsifiable?
There may be, but it's important to remember that not all experiments can be conducted with live animals in a lab. There are entirely valid, falsifiable, scientific questions that can't be answered that way. For example, "Could T-Rex swim?" You can't get a live T-Rex and toss it in a pool beca use they're extinct.
Instead, you have to do what's called a "natural experiment"[1]. Lab experiments work like this:
1. Make a prediction.
2. Create a situation in a lab that generates new data.
3. See if the prediction predicts the data.
A natural experiment is:
1. Make a prediction.
2. Dig up old but previously unknown data.
3. See if the prediction predicts the data.
For Jayne's hypotheses, you need to unearth things created by early humans and see if ones older than his predicted point in time show bicameralism while newer ones don't.
This is challenging because we just don't discover artifacts with sufficient detail in that way very often. But difficult-to-falsify-because-of-lack-of-evidence does not mean it's not a valid scientific question.
It's entirely scientifically valid to wonder about the mating behavior of prehistoric soft-bodied organisms, but we'll likely not be successful simply because they're poorly preserved in the fossil record.
> Ok, let's forget rats for a moment. Try to apply this to a closer relative: chimps
Chimps are not the same thing as early humans. Experiments on them doesn't tell us any more than experiments on chickens tell us definitive things about dinosaurs.
[1]: http://en.wikipedia.org/wiki/Natural_experiment