The sympathetic nervous system was thought to have evolved with jawed vertebrates. But lampreys—jawless, parasitic fish that suck out the blood of their hosts—have a simple one, per recent research.

With terrifyingly sharp teeth arranged around a circular mouth, lampreys look about as primitive a vertebrate as you could imagine. But a new study finds that the animals have a surprising similarity ...

Understanding how your body works can be the key to reducing stress. For example, you’re probably aware of your fight-or-flight response—the body’s way of preparing itself when it believes it’s being ...