Use multi-joint barbell exercises like squats and deadlifts. They build bone density and stave off the effects of osteoporosis.
Or just drink some milk for the calcium and go for long walks when you're in your teenage years (especially for females), and of course later as well.
You could add some wrist and ankle weights to enhance the effect, oh, and get some sun for the vitamin D.
Our bones don't have to be as strong as our ancestors were, they just have to be strong enough to get us through our lifetimes without breaking down.