Actually, Senoufou, our teeth have evolved very well, but not necessarily to cope with a modern diet of soft food and lashings of sugar that turns to acid as soon as it hits your mouth. Can't blame our poor old gnashers if we abuse them so. Funny thing, though, evolution. We've got so good at making people live longer that bits of us that at one time might have done us proud for thirty or forty years now struggle to cope into our sixties, seventies and beyond, teeth, backs, eyes, ears. We've only achieved the spectacular increase in longevity over the last couple of hundred years or so, but, as generation spans are very long for humans, evolution hasn't kept up and it may never will. In the past, weak teeth, eyes or early-onset arthritis would have quickly seen you off and you wouldn't have had time to do much successful breeding (high child mortality rates wouldn't have helped). These days you can conceive even though you have a full set of dentures, you're stone deaf and can hardly find the bed. We're very good at keeping people alive, far less good at keeping them in MOT condition.