What's the most amazing thing the human body does that people have no idea about?

Humans don't have what is commonly referred to as "free will." Important to note that we have something like free will and we do have agency.

Before you are cognizant of your decision on how to react to a situation, there are indicator neurons in your brain that are firing that predict the decision you'll make. So by the time you say "Hmm, A or B? I'll choose... B." the choice has already been made. Hundreds or tenths of seconds before you present yourself with the illusion of the choice.

There's a lot more detail I could add on this but I'm trying to keep it short. Check out http://www.technologyreview.com/featuredstory/528136/searching-for-the-free-will-neuron/ if you want to know more.

Also TIL that bones that regrow will not be stronger than their predecessors. http://www.nytimes.com/2010/10/19/health/19really.html

Nor do bariatric (fat) patients have stronger bones than average humans. http://www.mayoclinic.org/medical-professionals/clinical-updates/endocrinology/obesity-bariatric-surgery-and-bone-health-still-much-to-learn.

Also check out the Danger: Humans video https://www.youtube.com/watch?v=OcPqk-O-fD4 for similar topics. It's exciting to think about how aliens might perceive humans:

Humans can perceive some electromagnetic radiation, and often seek it out.

If the human's body perceives itself to be poisoned, it will automatically begin evacuating potential toxins.

Humans flash their bone protrusions at each other to communicate.

Humans will capture the young of other terrestrial species and use them for their labor, meat, or domestic utility.

Human females store their young inside their abdominal cavity for up to nine months.

/r/AskReddit Thread