In the 70's, while working on Days Of Heaven, Malick came up with a project he simply called 'Q'. It was a story that involved some soldiers in World War I, with a prehistoric prologue that centered on the beginnings of mankind. Later, after Malick sent somebody to scout locations, he decided to ditch the whole "war" part of the story and focus on the "prehistoric".Looks like it is worth keeping an eye on.
That film now has a working title, "Tree Of Life". It also has a couple of names attached to it - Mel Gibson and Colin Farrell. The plot is very secret, but it seems to focus on the beginnings of mankind and our evolution.
According to IMDb Pro, "Tree Of Life" also has a $145 million budget, which is large by any director's standards, let alone for Malick.
Update: Dang, doesn't Peter Chattaway sleep?! He had a post up on this one at 12:31 a.m. this morning.