The Book of Exogenesis: In the beginning was the word, and the word was a meteorite…
Earlier this month, a report, based on NASA studies of meteorites found on Earth, suggested that some building blocks of DNA may have been formed in space.
As it turns out, DNA components have been found on meteorites before, but it’s never been entirely clear if the space rocks came to Earth bearing these molecules, or if they were contaminated upon arrival. Furthermore, this recent study of meteorites was the first to discover trace amounts of three molecules — purine, 2,6-diaminopurine, and 6,8-diaminopurine — which, as nucleobase analogues, provide us with the first piece of solid evidence that the compounds in the meteorites came from space and not terrestrial contamination.
This news, which propagated wildly through the blogosphere in its own form of directed panspermia, led me to bone up on its potential ramifications: what do DNA-saturated space rocks imply about the inherent properties of life? Do they support the theory of panspermia, or exogenesis?
The idea of panspermia has been around since the Greek philosopher Anaxagoras posited that the universe is made of an infinite number of spermata (seeds), coining the word “panspermia,” or “all seeds,” in the fifth century B.C. Shortly thereafter, Aristotle debunked Anaxagoras, putting forth a theory of spontaneous generation that held sway for over two thousand years. Since then, the idea has gone rogue, popping in and out of scientific and popular consciousness; it can be found in the writings of Berzelius, Kelvin, von Helmholtz and the Swedish scientist Svante Arrhenius in the early 1900s.
The British astronomer (and science-fiction writer) Sir Fred Hoyle, in cahoots with collaborator Chandra Wickramasinghe, argued that “terrestrial biology is not a closed system.” He further maintained that not only is panspermia responsible for the origins of life on Earth, but that life-forms continue to enter the Earth’s atmosphere in “genetic storms,” and may be the key factors in the genetic novelty necessary for macroevolution. Hoyle was a scientific heretic — rumor has it he was denied a Nobel prize because of his zeal for spaceborn primeval molecules — and panspermia, as a theory, has always relied on hard-to-procure evidence of extraterrestrial life to have any real credibility. Both factor into panspermia’s sticky dubiousness, and hence a concrete fragment of corroboration, like molecular compounds on meteorites, is a significant boon to this oft-maligned idea.
Of course, the “DNA meteorites” are not a smoking gun. Allow me to emphasize that the discussion I’ll endeavor to have from this point forward will not be a rational extrapolation of the evidence at hand. Rather, I’m tugging at a loose, lunatic thread, gently pulling it across the room, seeing how it damages the weave, and ultimately trying to unravel something fundamental about the nature of life.
The question of the origin of life is at the root of considerable human endeavor: scientists work collaboratively over generations in the hope of parsing a concrete answer, theologians draft dogma, and artists celebrate the beautiful implausibility of the problem, honoring it each time they too make something from nothing. Why is panspermia — the notion that life exists throughout the Universe, distributed by meteoroids, asteroids and planetoids — any stranger than a touch from the Heavens, or a spontaneous spark in the primordial stew? The notion that life on Earth might have emerged, not from some local organic or mystical process, but from elsewhere, remains eccentric, marginal, and near-conspiratorial.
We may have difficulty conceiving of the Earth as anything other than the point of origin for consciousness, the shining beacon of life in a cold, dead universe. We see ourselves as Life, precariously existing on a pale blue dot that floats like a “mote of dust” in an infinite black vastness of Death. It’s important to remember, however, that there’s a difference between death and the absence of life. The universe is made of rocks, gas, and ample amounts of inert matter, but it isn’t dead — it’s simply not alive. Life articulates its absence, which is to say, the universe appears to be dead, but only because it might kill us.
So, while we may imagine that meteors cutting through space*, burdened with genetic code, are arks of capital-L Life in a universe black with death, they are in reality life and death, birth, awareness, the seeds for conscious beings to spring forth and consider the question, the full spectrum of the conceit; the universe is just the substrate.
Perhaps panspermia also irks because life-from-elsewhere offends our human chauvinism. After all, the suggestion that we might exist thanks to an external catalyst reframes the narrative of human evolution, and of future human propagation out into the universe, from something like this:
To something more like this:
This changed narrative that the DNA meteorites imply — a story in which humanity and all its grand pursuits is simply a waypoint in the journey of intelligence across the cosmos — doesn’t diminish the mystery of life. Rather, it widens the net, blooming the question outwards.
Life still had to emerge from non-life somewhere, sometime. To conceive of that occurrence on the home front is simply to displace the miracle; whether the spark occurred on Earth or not is immaterial. If anything, it’s a bigger, better mystery — one which is best appreciated if we think of if not as members of the human race, or even as denizens of the terrestrial biosphere, but as representatives of a vaster lineage: the living.
Evolution from Space: A Theory of Cosmic Creationism, by Sir Fred Hoyle and Chandra Wickramasinghe
The Biological Big Bang: Panspermia and the Origins of Life, collected essays including writings by Svante Arrhenius and Chandra Wickramasinghe
*Personal admission: I’m very nearly shattered by the idea of life as a variable of chaos upon an unfeeling backdrop of dust and gas.