"Our Earth condensed out of interstellar dust and gas ~4.6 billion years ago,
and life emerged ~4 billion years ago. The 0.6 billion years before the
appearance of life were the years of chemical evolution on Earth, leading to the
gradual appearance of life as an emergent
phenomenon. Lightning and UV rays from the Sun broke up the simple
hydrogen-rich molecules and the fragments combined into increasingly complex
molecules. These dissolved in the oceans and moved around, interacting in
various ways. Given enough time even a rare event may occur. One such event was
the chance emergence of a molecule that could use the smaller molecules floating
around in the organic soup to make crude copies of
itself. This was the ancestor of DNA, and the rest is history"