[edshuck]

I think there are two items of investigation that will prove useful in answering the question.

First is DNA. I read, and I do not recall the exact number, that all DNA plant or animal is over 90% exactly the same.

Suppose some DNA traveled on a rock from space. Some odd combination exists that allows the "reactivation" of the DNA and variants form.

Then there is thread theory. That gets deep, quick. But it is about among other things, parallel universes. if there is a 1st, 2nd, 3rd, 4th dimension. Why not more?

Reply to some of the above. Maybe we are on a petri dish and the aliens are timing us til we are out of food or die in our own waste.