Lots of people have crooked teeth. Scientists think that this is chiefly because our jaws and teeth are getting smaller, but the jaws are shrinking faster than the teeth. Crowding can start from a very early age. Many parents are shocked when their child, who had perfectly straight baby teeth, develops crowding once the teeth start to change. This is because the permanent teeth are much larger than the baby teeth and unless the baby teeth were well spaced out, crowding is almost inevitable.