Squats are incredibly good for you. Probably the best body lift out of all of them. You can't go to high in weight too fast(biggest mistake people make) and you need to have good form(next biggest mistake because of lower back and knee injuries) but dude- its exercise science. Your body responds to squats by building every muscle group in the body. It is one of the few compound exercises that makes your whole system respond.
It is also one of the few exercises that helps build up your cardio response. This means it actually helps your heart become more efficient.
I will let Vek who is a mechanical engineer and a superb athlete provide scientific data. He is good on that. However, in nearly every small town in the midwest old time strong men have been doing squats to stay strong through early, middle and old age for as long as our nation has been in existence.
Most people my age(48) have had knee and back problems through carrying heavy weights for long trips. I get sore knees if I have a 20 mile packout but squats build up connective protective tissues around your joints.
