Scientists have long held life on Earth began to flourish some two billion years ago. New research, however, has found evidence that suggests life started much earlier.

Researchers from the University of Washington studied some rock samples that dated three quarters of the estimated lifetime of the Earth. They found that early microbes might have made their way from the ocean to land by taking nitrogen from the air about 3.2 billion years ago.

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Nitrogen is necessary to support life since everything from viruses and bacteria to complex organisms use it build genes.

The process that allows organisms to use nitrogen in a form that can support larger communities, called nitrogen fixation, didn't develop until two billion years ago. This led to a theory that the oldest ecosystems were just hanging on in an inhospitable planet. 

Research, however, shows there was no nitrogen crisis on the early Earth and the planet could have supported a large and diverse biosphere.

Researchers analyzed 52 rock samples from South Africa and northwestern Australia. The samples are the oldest and most preserved rocks on the planet, and range in age from 2.75 billion to 3.2 billion years old.

Formed before the atmosphere gained oxygen, or about 2.3 to 2.4 billion years ago, the rocks preserve chemical clues that were removed in modern rocks. The rocks were also formed from sediments deposited on continental margins, making them free from chemical irregularities.

The oldest samples suggest life was apparently pulling nitrogen out of the air.