The human race began as microbes brought to Earth by comets millions of years ago according to a British scientist, The Sun reported Wednesday.

British professor Chandra Wickramasinghe said: "We are all aliens. We share a cosmic ancestry. Each time a new planetary system forms, a few surviving microbes find their way into comets. These then multiply and seed other planets. We are thus part of a connected chain that extends over a large volume of the cosmos. Evidence is pointing inexorably in this direction."

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Proffesor Wickramasinghe, an astrobiologist at Cardiff University, believes the first "seeds of life" were deposited on Earth 3,800 million years ago. He said life through the universe was transferred from planet to planet over billions of years as comets hit them and pushed matter into space.

But Wickramasinghe accepted that the theory did not explain how life originally came into being.

He and his late colleague -- astronomer and science fiction writer Sir Fred Hoyle -- championed the theory of panspermia from the 1960s. It says that life did not start on Earth but was brought here from space.

The professor added, "Although we have no definite knowledge how life started in the first place, once started, its spread in the cosmos and survival is inevitable."

Read more at The Sun.