The science behind 'runner's high' and why marathoners might feel it more

Monday is the 128th Boston Marathon, which means you’ve probably heard people talking about “runner’s high”: a sense of euphoria and relaxation runners feel when they’ve been running a long time.

Not only is a real thing, but it has roots in human evolution.

Dan Lieberman, an evolutionary biologist at Harvard University, breaks down the science and origin of the runner's high.