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5. Life
What makes life so special? Is there life elsewhere in the Universe? And how exactly did life emerge and diversify? In many ways these remain mysteries, but we do have enough evidence to explore some possible answers.

5.0 Life and big history

The young Earth was a dangerous and unfriendly place. Deep in the oceans, though, conditions were perfect for the emergence of life.

5.1 What is life?

Among living things, there are strong similarities and remarkable differences, many explained by the amount of shared DNA. But what does that really mean? What is life?

5.2 How did life begin and change?

The appearance of life marked a profound beginning. Over time, simple life forms transformed, evolving into complex organisms.

5.3 How do earth and life interact?

Life can be fragile. The continued existence of a species can depend on even the slightest changes to astronomical, geological, and biological conditions.

5.4 Ways of knowing: Life

The history of our planet is written in rock record, along with clues about the future. Rock detectives – geologists – study these clues and often observe Earth’s changes first hand.