(PhysOrg.com) -- Arizona State University researcher Paul Davies shares his theory about cancer being our evolutionary ancestor.

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Before the Cambrian flowering of multicellular life, there was a period of about a billion years where cells began to get together and form rudimentary colonies, says Davies, an astrobiologist who is one of two scientists proposing a theory that suggests cancer cells are living fossils.

"These rudimentary colonies, I think, were like the earliest tumors. So when people get cancer now, these tumors represent a throwback to that time about a billion years ago  that first experimentation with multicellularity," Davies says.

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