The first life on Earth is believed to have appeared at least about 3.5 billion years ago, with possible evidence suggesting it could be as early as 4.1 billion years ago. This period comes not long after the formation of the oceans (around 4.4 billion years ago) and the Earth's formation (about 4.54 billion years ago).

Earliest Evidence of Life

• The oldest undisputed fossils are stromatolites dated around 3.5 billion years ago.
• There are geochemical signs such as biologically fractionated carbon isotopes in rocks and minerals that suggest life might have existed around 4.1 billion years ago.
• Some microfossils and geochemical signatures indicative of life have been found in rocks dating back 3.4 to 3.8 billion years.

Scientific Context

• Life likely began soon after the Earth cooled enough to maintain liquid water.
• The period between about 4.3 billion and 3.7 billion years ago is when conditions may have become suitable for life.
• Some scientists hypothesize that life could have started even earlier but was destroyed by catastrophic impacts during the early heavy bombardment phases.

In summary, the first life appeared on Earth over 3.5 billion years ago, with some evidence pushing the origin of life closer to 4.1 billion years ago, shortly after the planet and oceans formed.