The Earth is billions of years old and was once a very hostile place. Eventually, a single cell was formed that evolved and reproduced. What conditions produced this first life on Earth?
- Evolutionary Theory suggests that all forms of life evolved from one ancestor - the first cell.
- 4.5 billion years ago, conditions on Earth were similar to that of Venus, with very little oxygen.
- It is thought that hydrogen, methane and ammonia in the Earth's early atmosphere combined with the oceans to form a prebiotic soup.
- Exposed to ultraviolet rays of the Sun, the prebiotic soup reacted to form organic compounds such as DNA - the building blocks of life.
Charles Darwin, The Origin of Species (1859) - "All organic beings have descended from... one primordial form, into which life was breathed."
This theory of evolution - known as "universal common descent" suggests that humans are not simply evolved from an ape like ancestor... our heritage goes much further than that.
It suggested that all living things, from insects to elephants, dandelions to humans, have evolved from one single ancestor - the first cell.
The Earth is estimated to be 4.5 billion years old.
Long before life began, the Earth was a very different place.
Many question how life could begin or survive in such a hostile environment.
The atmosphere contained very little oxygen and was mainly made up of hydrogen, methane and ammonia.
Earth's early atmosphere: Hydrogen, Methane, Ammonia
Very similar conditions to the lifeless planet Venus.
However, it's thought that these gases would have combined with the waters of the oceans, forming a chemical brew, known as the prebiotic soup.
This soup would have been exposed to scorching ultraviolet rays from the Sun... beginning a chain of chemical reactions.
In these conditions, simple compounds will have interacted to form more complex molecules.
From nonliving matter, new organic compounds such as amino acids and DNA would have formed - the building blocks for life.
Eventually, some 3.5 billion years ago, these components would form into clusters, or bubble-like structures, which would grow and divide, and become capable of producing and converting energy.
Life had begun.