A small digression
If you will permit me to reply to myself with a small digression to waste your time...
I was watching a discussion program on the tellybox ten years ago. About animal testing. And there was a young animal rights campaigner getting very animated about how all animal experimentation was cruel and should be immediately banned and replaced with computer modelling.
Which is basically a bollocks argument, becuase of the points I made above. We don't understand the underlying biology well enough to do this yet. We're still making mistakes, even though we're getting better.
Anyway his argument got shot down by another guest who had severe Parkinsons disease. And who said that his treatment had been developed on live gorillas - basically they practised the brain surgery techniques on them first. So the most problematic type of animal research - vivisection on higher primates.
While he was saying this he reached into his pocket and pressed a button. And he instantly transformed from a normal bloke, talking and gesturing, into this hunched and totally rigid figure, barely able to control his movements. Then he very slowly inched his hand back to his pocked and pressed the button, and instantly transformed back. He's got electrodes wired into his brain, which he'd turned off - which I hadn't even realised was possible at the time. And they stopped his muscles from going into involuntary spasm.
Our understanding of the brain on a physiological level is still pretty low sadly, so I can't see us being able to replace animal testing for drugs or surgical procedures for decades to come.