The biological process which lead to intelligent life on earth was a fluke that is unlikely to have been repeated anywhere else in the universe, claims Professor Brian Cox

The biological process which lead to intelligent life on earth was a fluke that is unlikely to have been repeated anywhere else in the universe, claims Professor Brian Cox.

The presenter and scientist blames a series of 'evolutionary bottlenecks' for the lack of extraterrestrial life on other planets, despite there being a mind-bogglingly vast number of them in the galaxy.

Humanity miraculously overcame them in a chance binding of two single cells merging somewhere in the mists of time, he said.

'There is only one advanced technological civilisation in this galaxy and there has only ever been one - and that's us. We are unique.

'It's a dizzying thought. There are billions of planets out there, surely there must have been a second genesis?

'But we must be careful because the story of life on this planet shows that the transition from single-celled life to complex life may not have been inevitable.'

He made the claims in an episode of BBC's Human Universe, adding that yet another freak occurrence - the meteor which wiped out the dinosaurs - allowed mammals and ultimately humanity to dominate the planet.

On the subject of the genesis of complex life, he added: 'We still struggle to understand how this happened. It's incredibly unusual.

'We're confident this only happened once in the oceans of the primordial earth.Life here did squeeze through.'

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Last month scientists claimed that our best chance of finding alien life is not looking for living animal organisms but rather plant life.

Two astrophysicists have said we should be looking at exoplanets for signatures of chlorophyll, which plants use to convert sunlight into energy.

And they say this could be done by a future telescope planned by Nasa to study habitable exoplanets.

If there are no aliens, humanity will never have to face the nightmarish xenomorphs of Alien (left), nor the benevolent E.T. from Speilberg's hit film

Princeton University astrophysicists Dr Timothy Brandt and Dr David Spiegel made the suggestions in a paper called 'Prospects for detecting oxygen, water and chlorophyll on an exo-Earth.'

They say that it might be possible to detect signatures of water, oxygen and chlorophyll on an alien planet.

One hundred million worlds in our galaxy are able to host alien life, according to a 'conservative' prediction by Nasa.

And the space agency claims that we will be able to find that life within the next 20 years, with a high chance it will be outside our solar system.

During a public talk in July in Washington, the space agency outlined a roadmap to search for life in the universe using a number of current and future telescopes.

'Do we believe there is life beyond Earth?' said former astronaut and Nasa Administrator Charles Bolden during a talk in Washington.

'I would venture to say that most of my colleagues here today say it is improbable that in the limitless vastness of the universe we humans stand alone.'