= new reply since forum marked as read
The first step being "The Big Splat" where a very large mostly water bearing planetoid (it has a name in the literature, too lazy to look it up) collided with the proto-Earth. This event is thought to have created the Moon. Also, it left an unusually large amount of water for a planet in the inner Solar system.
Secondly, the advent of anaerobic microbial life capable of existing in a harsh acidic environment. (now, whether it formed on Earth or was brought here is an open question) One of the by-products of the metabolisms of these creatures is oxygen which turns out to be a requirement for other higher forms of life. This stage took a heck of a long time, but, eventually these critters had changed the Earth's atmosphere with their output to the point it became toxic to them and they became a minority life form in favor of oxygen tolerant microbes. But, that is a whole other hypothesis.
The role the large ratio Moon played in this whole thing is manifold. It acts to partially shield the Earth from large impacts. Which creates the large periods of relative climactic stability needed by organic and inorganic processes to form a consistent atmosphere. It also acts to gravitationally stimulate the various structures and stratigraphy of the Earth to keep it from 'dying'. Similar to what has happened on Venus and Mars. This stimulation by the large Moon is also thought to keep the water present and atmosphere on the Earth from 'evaporating' from the planet and diffusing into space.
I thought I'd add this clarification and depth to my hypothesis. Seeing as how I'm getting pretty beat up for having my own hypothesis and the audacity to post it on DU without some sort of credentials.
Crucial.
I'll add it to the list.
