[adorno]

In fact, the newfound crater, in Egypt, was likely carved by a space rock that was itself roughly 0.75 miles wide in an event that would have been quite a shock, destroying everything for hundreds of miles.

It seems that with this crater from a space rock and all of the other similar collisions that the earth has endured during its history, that there should be no signs of life on the planet.

[Old Sarge]

There was one theory I heard, long ago, that Earth was fertile, but lacked that spark for life to begin - kind of like an unfertilized egg.

Without the event of the meteor collisions, the essential element(s) for life weren't present.

[RightWhale]

there should be no signs of life on the planet

It might be interesting to note that these monstrous disasters are often associated with subsequent explosion of new species.