Three things I know...
1. Man has been obsessed since the beginning of time with attempts to understand (superstition, religion and science) himself and his environment. No absolute consensus has ever been reached, but there have been enough divergent explanations as to nullify the possibility that a consensus will be reached anytime soon.
2. Sunlight feels good!
3. Man can not stay still for long and has always been on the move, migrating to the next nearest valley, river or ocean. In general, the further man migrated, the better things (food, water, freedom) got for the immigrating group and the worse things (food, water, freedom) got for the local inhabitants 'til the locals assimilated.
That's it... Those are the only three things I know. Sure, I've developed many opinions and suppositions along the way, but it would be an offense against humility and reason to say that I absolutely know anymore than that at this point in my life.
I can also say, "I knew a lot more when I was twenty-four."