The lucky tilt

Here's an interesting story from Physorg about the possible importance of planetary tilt for the emergence of life:

But take away the Earth's axial slant, and the place might become a lot less inviting.

With an obliquity of less than five degrees or so, an Earth-like planet's broader equatorial regions bear the full brunt of a sun's radiance. The polar regions also receive far less sunlight than they do with seasonal ebbs and flows. The result: extreme temperature gradients based on latitude. "Your equator is heated enormously while the poles freeze," said Heller.

In theory, bands of habitability in temperate, mid-latitude zones could persist. In a worst-case scenario, however, the entire atmosphere of a zero-obliquity planet could collapse, Heller said. Gases might evaporate into space around the planet's blazing middle and freeze to the ground in the bleak north and south.

Life, had it ever emerged, would be stopped dead in its tracks.

And the problem is, for life on other planets, that red dwarf stars may well erase planetary tilt relatively quickly.

It sounds like it may be an important reason as to why you can have billions of planets, but not many suitable for life.