The fossil record shows that within 200 million years of the cooling of the primordial Earth, there was life, leading some biologists to speak of “instant” life. Unfortunately for this view, the mathematics of the situation create a dim view of its possibility. Two hundred million years is a virtual blink of the eye in geological terms. As we achieve better resolution of this challenging slice of the fossil record, the gap continues to close and we find life farther and farther back towards the point of Earth's origin.
And what if the origin of life should precede the origin of the Earth? A strong case can be made that life evolved in the reaches of deep space, then drifted here as single-cell microorganisms and viruses which evolved as best they could from there. We have seen plenty of good arguments for what could keep such microscopic spacefarers alive through the radiation they would encounter in space. Maybe they become freeze-dried from space conditions and remain dormant for billions of years. It has been argued that these single-celled organisms could survive the entry into an atmosphere and then set up shop.
Scientists are always discovering new places they never thought they would find life, but lo and behold, something is growing there—on reactor cores, inside rocks, in underwater toxic steam vents; the most inhospitable environments, time and again, are found to be just crawling with life. The list for what life needs, in order to take hold, keeps getting shorter and shorter. Some people say you might not even need water for some kinds of life.
They used to think maybe only Earth had life. Can you imagine? Well, that would make us the Man, wouldn't it? “You the Man! You the Man!” This kind of thought is pretty typical for our species. It is an anti-Copernican idea, which is to say, it is an idea that somehow makes Earth the center of the universe.
We prefer Terence McKenna's vision of the mushroom spores, percolating up into space, becoming freeze dried and getting picked up by the solar wind where someday, blown to other planets, they take their chances.
Hell, there is potentially life on every rock in this solar system.
The theory that life arrived here from elsewhere (the “panspermia” theory) has a distinguished pedigree, originating with the Swedish chemist and Nobel-laureate Svante August Arrhenius in 1907. The science behind the theory has changed somewhat but it continues to receive robust support from a vocal minority of scientific heavy-hitters, including the famed co-discoverer of the DNA molecule, Nobel-laureate Francis Crick himself. The idea's most persistent modern advocates have been astronomers Fred Hoyle and Chandra Wickramasinghe, who frame the argument in mathematical terms. It goes like this: to evolve biological life you must first evolve about thirty critical enzymes. The problem is, these enzymes are all terribly complex molecules. The odds of any one of them occurring by chance in the young Earth's prebiotic organic soup are astronomically slim. But you need thirty, which only worsens the situation. The way these guys see the math, it's like having a tornado blowing through a junkyard and producing a fully functional 747.
You would essentially be waiting around for billions upon billions of years for these enzymes to finally form themselves, and then to get themselves together into a living cell which can commence to evolve. And the fossil record shows these primitive cells were already going full-bore as soon as the Earth ceased to be molten about six billion years ago. The conclusion we are left with is that life may very well be adrift on the winds of space, just waiting to touch down. In this view, viral and bacteriological life is in fact still touching down, causing disease and whatnot, spurring evolution on as genetic material is exchanged between them, as is known to happen on Earth.
There is in fact empirical infrared evidence of biological material flung far between the stars, with spectra from space closely matching that of Earth-borne bacteria. In particular, low-temperature areas in molecular clouds could produce large molecules, and with all the time in the world, become cosmic hatcheries. Every new experiment seems to support the idea. It's evolution from space, baby.
Recommended Reading: Anything by Fred Hoyle and Chandra Wickramasinghe, but especially Evolution From Space , Diseases From Space , and Living Comets .
(A version of this piece appears in our book Gonzo Science: Anomalies, Heresies, and Conspiracies and on the Gonzo Science CD.)