Ribs don't do a very good job of protecting our organs

Many murder mysteries feature a corpse with a dagger through its ribs; obviously, the ribs do not do a perfect job of protecting the organs inside them. Better protection could be provided by a solid bony case like the skull; can you see any disadvantages in such an arrangement?

Thanks in advance!

Ribs move every time we breathe or change our posture. It'd be like being in a tightly bound corset 24/7.

Evolution didn't have to contend with sharp objects purposely being driven into the chest. Could you imagine the feeling when your niece jumps on your chest and you don't have ribs? You may just be dead. Ribs are there to provide support and protection from most of what nature can throw at it. If it were a solid cage, could you imagine 1) how difficult it would be to breath with no bony movement 2) how much heavier you would be and top heavy in particular and 3) how difficult it would be to move your upper torso? I think the rib cage is the perfect compromise between protection and freedom of movement.

We wouldn't be able to move our torsos at all.

Yes maybe we will ivolve

I don't understand....do you want us to verbally bash the ribs or what?