Life started almost as soon as the planet was formed - somewhere between 3.8 and 4.1 billion years ago.
Hyperthermophiles at the base of the Phylogenic tree of life.
- wikipedia 
It started in a violent world, and even today we can find primitive life forms (Extremophiles), that inhabit such wild and violent environments.
Black smoker at a mid-ocean ridge hydrothermal vent
- wikipedia 
Abiogenesis (Brit.: /ˌeɪˌbaɪoʊˈdʒɛnᵻsᵻs, -ˌbaɪə-, -ˌbiːoʊ-, -ˌbiːə-/ AY-by-oh-JEN-ə-siss or AY-bee-oh-JEN-ə-siss) or biopoiesis or OoL (Origins of Life), is the natural process of life arising from non-living matter, such as simple organic compounds. It is thought to have occurred on Earth between 3.8 and 4.1 billion years ago, and is studied through a combination of laboratory experiments and extrapolation from the genetic information of modern organisms in order to make reasonable conjectures about what pre-life chemical reactions may have given rise to a living system.