The cause(s) of pyramiding is a highly debated topic. I know of no definitive research that can fully answer your question. However, when all other husbandry issues are equal, keeping a baby warm, humid, and well hydrated promotes smooth shell growth. This seems to be especially important in raising sulcata and leopard tortoises. To what degree it applies to other tortoise species I am not sure. If you search the forum for "pyramiding" you will get hours of reading on the topic.