Some researchers have made an interesting connection: if you measure the complexity of life or how big the genome is you find it increases at a rate that seems exponential. It's very similar to Moore's law, which suggests the number of transistors over the same surface area on a chip doubles almost every two years. You can extrapolate both forward and background. Eventually, if you extrapolate down enough you'll find the point of origin. In other words, it's possible to estimate when life first appeared based on life's complexity graph.
“Linear regression of genetic complexity (on a log scale) extrapolated back to just one base pair suggests the time of the origin of life = 9.7 ± 2.5 billion years ago,” they say. It's like saying life is 10 billion years old give or take 2 and half billion years. But, wait - isn't Earth only 4.5 billion years old? And life for sure couldn't be possible during the planet's first hundred million years when it was all a big blob of molten rock. It may seem, then, that life didn't take a fully exponential path from origin to present day. It may have had periods of altered rate of complexity - sometimes evolution may have driven complexity faster and at other times slower. In this case - the 10 billion years estimate - maybe life had such an explosive rate of growth that it squeezed the whole timeline into the age of Earth.
Alexei Sharov at the National Institute on Ageing in Baltimore and Richard Gordon at the Gulf Specimen Marine Laboratory in Florida, the two authors of the study, aren't convinced. Citing evidence that suggests bacteria can survive for millions of years trapped in ice, the researchers think it's quite possible that life came from another solar system; life would only continue a process that began at least 4 billion years earlier. It's also another possible answer to the Fermi Paradox (the second in a day, what are the odds?) : we haven't heard from any extraterrestrial intelligent creature because complex life - the kind resembling humans - is still a work in progress. Maybe we humans are, in fact, the very first technologically advanced species in the Universe, or merely among other pioneering life forms. The kind that knows how to emit radio waves, at least.