Here's some things that people really believed in the past, and maybe some still do:

Having your picture taken steals your soul.

That smoking is good for your digestion.

If you swallow gum, it will take seven years to digest.

That it's OK to pay women less than men for the same work. (79 cents on the dollar)

That if a girl used her brain too much, she wouldn't be able to have babies later.

The earth is flat.

If you swallow a watermelon seed, the watermelon will grow inside you.

Drinking radioactive water will heal your ills.

Heroin is great for a cough.

Blood letting will cure you of numerous ailments.

Cocaine toothache drops are great for kids.

Plague and malaria are caused by bad air.

I wonder how ridiculous our beliefs might look to our future progeny.