Where do children get their intelligence?

Are there increases in miscarriage rates, why are rats used in experiments, could we use developments in cartilage growth to treat scaphoid wrist fractures, is it safe to do strenuous exercise as you get older, where do children get their intelligence and what causes your stomach to flip when you go on a rollercoaster? Plus, scientists using nose cells grow new knee cartilage. Like this podcast? Please help us by supporting the Naked Scientists