Complex life's days are numbered

摘要

ONE billion years from now, Earth's atmosphere will contain little oxygen, making it unsuitable for complex aerobic life. Today, oxygen makes up around 21 per cent of Earth's atmosphere. Its oxygen-rich nature is ideal for large and complex organisms, like humans, that require the gas to survive. But early in Earth's history, oxygen levels were much lower - and they are likely to be low again in the distant future.