Lying

It must be hardwired into our humanity. I don't know how else to explain the fact that my almost four-year-old can't seem to stop lying about everything, from whether or not she washed her hands after going to the bathroom, to making up stories about what her teacher taught her at school to avoid helping with chores and refusing to admit it's a lie even when confronted about it. Where do we learn how to lie? Is it just part of our nature? Adam and Eve disobeyed God, but they at least were honest about their disobedience. No lying there. So what compells my child to lie? Fear? Anger? Sadness? Ignorance? Or, even worse... did she learn it from me?
Parents are constantly lying. Some lies are quite necessary, to keep the magic of childhood alive. I have never wished that my parents had raised me knowing what I know now about the Easter Bunny, Tooth Fairy, and Santa Claus. Other lies or omissions are helpful to keep kids safe, and as parents, we must use them. But beyond that, I try to be honest and real, so where does the lying come from?
Maybe the world of pretend? Ellie is constantly singing, talking to herself, and playing in some world where no one else is allowed in. It seems as though she's testing the boundaries of her world, seeing how far she can take her made-up reality into the real world.
But it still doesn't make it ok. How do I teach a preschooler to not lie?