It seems obvious that turtles' shells would have evolved to protect them from predators, but researchers have found that they probably first evolved to help turtles dig. Learn what that's all about in this episode of BrainStuff.Learn more about advertising on the HowStuffWorks podcasts at www.howstuffworks.com/advertisers.htmAnd to learn about your ad choices when listening to podcasts, visit https://www.howstuffworks.com/privacy.htm#ad-choices
