Alien Biology on Earth

An octopus runs on hardware nothing like ours. It has three hearts, blood that is blue rather than red, and no skeleton at all. Its blood uses copper instead of iron to carry oxygen, which is what gives it that blue tint.

The stranger part is its mind. The line that led to octopuses split from ours around 600 million years ago — roughly as far back as the family tree of animals goes. So whatever intelligence an octopus has, it built on its own, with no shared blueprint from our side of life. No other animal on Earth is put together so unlike us.