Mankind's favourite topic has always been mankind. You could say that's why we invented science in the first place - to find out more about ourselves, the world, and how it relates to us.
We've found out a lot of useful stuff, like how you turn bagels into energy and poop and how to kill nasty bugs before they kill us, but along the way we've also found some strange, surprising and even straight up creepy things about human nature that no one was expecting.
Turns out that we're a complex bunch and, just when you think you've got it all figured out with your theory about the nature of the soul or the structure of the brain, the universe throws you a curveball and leaves you back at square one.
One of the most complex and intriguing areas of study is the brain. We're still working out the final details of how this squashy mass of cells functions - you know, small stuff like how in god's name does it work?
Tackling the big question like "Who am I?", "How did we get here?" and "What is life anyway?" was never going to be easy, but some of the theories that have been put forwards in response range from the outlandish to the thought provoking to the downright bizarre.