There is a theory that the apes humans evolved from only did so because they started scavanging animal carcasses. The meat resulted in a protein surge in their diet and because their bodies didn't require all the extra protien, like a tiger does just to keep it's near 1000 lbs. going, it caused the apes' brains, over time, to increase in size and function. I don't really remember much more of it, though it did have something to do with the ability to also fend off predators. Of course a Theory is an educated guess and I'm not sure if I believe it either.
I am a spiritual person but I don't believe in a god (though I do not fault anyone who does). Let's just say that what I believe is impossible to explain but easy to understand.