While individual trajectories of non-linear systems are not predictable, they all end up on an attractor and usually all we are interested in, is the attractor.

While individual trajectories of non-linear systems are not predictable, they all end up on an attractor and usually all we are interested in, is the attractor. That is when performing a test on a mouse we are not measuring what a particular mouse would do, but what the mice do on average. So as long as model behaves like a mouse it can be useful, even though it would not behave like any particular mouse. Also it's important to remember that the question is not about all or nothing, when we get a model most likely instead of 100 experiments on real mice we will be doing millions on virtual mice, and then 10 on real mice to verify the results.