According to a calculation by two noted biologists, life on Earth may not have come from Earth at all.
Alexei Sharov of the National Institute on Aging in Baltimore and Richard Gordon of the Gulf Specimen Marine Laboratory in Florida have reported that their recent work may point to extraterrestrial origins for Earth's earliest life.
The two plotted the genome sizes of different types of organisms against their currently theorized date of origin. From this, they determined that genome complexity doubles approximately every 376 million years. When they extrapolated this figure backwards, they determined that the origin of life on Earth would have occurred almost 10 billion years ago; well, well before Earth even existed.
The researchers concluded that life must have spent a good five billion years on a different planet before somehow arriving on Earth. They theorize that bacterial spores may have traveled deep inside of rocks that drifted through space after a cosmic disaster.
Sharov and Gordon also believe their idea accounts for the "Fermi Paradox," an idea that arose after molecular biologist Francis Crick theorized that an advanced extraterrestrial civilization "seeded" distant planets with early life forms. In response, Enrico Fermi inquired why we have not heard anything from these aliens; after all, they would know we are here.
According to this new theory though, the microbes were more likely launched accidentally from a primitive planet, perhaps as the result of some kind of impact or explosion, rather than on purpose from an advanced one. That could mean that we humans are the first to have reached this stage of evolution, or perhaps the only planet that did.
However, there are plenty who believe that these calculations don't prove much. The researchers' equation is reliant on the idea that life form complexity would double every 376 million years. It's very possible that these increases could have started off fast, and slowed down, or hit periods of exponential growth before steadying out.
Still, Sharov and Gordon are sticking to their idea, and believe we will find more evidence of this as we continue to study the surface of Mars. In either case, it's an interesting idea to ponder about.