The amount of time it took life to form

[Forestman]

How long did it take life to form after the oceans had formed?

[Andy Resnick]

Oceans formed about 4 billion years ago:

http://serc.carleton.edu/NAGTWorkshops/earlyearth/questions/formation_oceans.html

The earliest evidence of life is about the same time:

http://rainbow.ldeo.columbia.edu/courses/v1001/7.html

So I'd say life started as soon as liquid water was around.

[Bob S]

Anaerobic life and prokaryotes predated eukaryotes, and plants for photosynthesis of carbohydrates, on which all (most?) animal life depend.