[NukeMan]

Venus has no moon and Mars has two much smaller ones orbiting a different frequencies yet Venus "tilts" much less and Mars only very slightly more. Back to the drawing board on this one.

I think this one is actually correct. Here is a good ref describing the stabilizing influence:
http://www.math.nus.edu.sg/aslaksen/teaching/hm/phase/ORIENTATIONOFTHEMOON.htm

The idea is that given mass of the earth, and its distance from the sun, a moon (the size of our moon) is important for obliquity. You want some small variation in energy deposition to the planet (polar vice equatorial) but not too much. Climate (and therefore the chances for multicellular life) then depends in a complicated way on the tilt. Mars & Venus show strong evidence of catastrophic (for life, anyways) changes in obliquity in the past because of a lack of a sizeable moon.

[edsheppa]

Thanks, but there's no explanation of how the moon stabilizes the Earth's tilt. Perhaps it's too complicated. But curious that Venus and Mars happen to not be extraordinarily tilted just at this time. Just more randomness I guess.

BTW, your reference has an interesting proposal that the Moon may once have been a mere 20K from the Earth. By my calculation that corresponds to an orbital period of about 0.35 days. Obviously then the tides would have been much larger (the Moon being so much closer) but also would have gone "backward" relative to how they go today. (IOW they would propogate around the Earth faster than the Earth's rotation.) My intuition is that in that circumstance the Moon would have been attracted toward the Earth by tidal friction - the opposite effect of today with the Moon eventually crashing into the Earth. I'd conclude that, unless the Earth's day was very much shorter than today's, the Moon was never so close.