In the beginning

Living things breathe, feed, grow and leave offspring. They range from the simplest single-celled bacteria to plants, birds, animals and humans. Earth is the only world we know that supports life. No one knows how life began. It seems to involve the coming together of certain chemicals. But what changes these chemicals into life-forms is a mystery.

Studies of ancient rocks have shown that life began on Earth about 3 800 million years ago. At that time, the Earth was a very unfriendly place. The air was dense and poisonous. Comets and meteorites were raining down on the planet.

The Earth was a water world with no dry land. 30 years ago, scientists thought that life began in the lakes and oceans.

Lightning and ultraviolet light from the Sun split the hydrogen-rich gases in the atmosphere. The pieces joined to become larger, more complex chemicals.

These chemicals collected in the oceans, forming an 'organic soup'. One day, an accident occurred. A molecule began to make copies of itself. Earth had sprung to life.