Lenses of the Universe
Biological life is somehow very probable on Earth. Even when many species have been extinct, other species emerged, unexpectedly similar, however different. Many of them had backbones, one mouth, two eyes, nails. It is like... life is bound to exist only reusing similar patterns, at least in this time frame. Once the Earth was too hot to sustain life. Someday it will again be too hot or too cold for life. But for now all is ok, Earth seems to have the right balance of atoms in the air and in the soil to make the life probable, you only need a seed. We can imagine that these conditions are very special. Would it life be possible in rather different conditions, even if the temperature allows and you manage to have water, oxygen, carbon, hydrogen? Would it still be probable to live rather than die if other minerals that we use today would be more scarce? Would life still work is some minerals are way more abundant? Would DNA create the same organisms we know when forced to re...