Earth won multiple lotteries, at the right time, in the right amounts. * Single-star system (not that common) * Away from galactic radiation in the center of

Earth won multiple lotteries, at the right time, in the right amounts. * Single-star system (not that common) * Away from galactic radiation in the center of the Milky Way * A stable, elliptical system without chaos or collisions * Optimal distance from the Sun * Optimal amount of water * Optimal size * Oxygen * Iron core to protect against radiation * The Moon, right size, right distance, to keep the spin stable * Gas giants absorbing a lot of dangerous projectiles before they get here Take out any one of these, and we are probably toast. Or take #2 - most of our galaxy is a radiation oven. This is probably true for many others, making the Universe predominantly hostile to life right off the bat. And, sure, life could mean something else, and different permutation of these or completely different variables might create life, but as far as we know - the Earth is a very, very unique place. We can see it in our own system, with "close but no cigar" Mars.