Another thing that amazes me.
For a long time the only life on Earth was bacteria.
To make the first complex cell, two unrelated bacterial cells had to merge to make an viable hybrid, something that should not be possible.

It happened on Earth only once, so every plant, animal fungus on Earth is descended from that one impossible cell.
Amazing!
http://www.newscientist.com/article/dn18734-why-complex-life-probably-evolved-only-once.html#.VVXWFvlViko