How did life begin? Two common answers come to mind. One is that, at some point, a deity decided to suspend the laws of physics and will a slew of slimy creatures into being. A second is that a one-in-a-trillion collision of just the right atoms billions of years ago happened to produce a molecular blob with the unprecedented capacity to reproduce itself.
If the first answer fails to convince atheists and agnostics, the second answer feels a like a bit of a letdown. Life on earth was dumb luck, or—depending on how you look at it—a cruel accident. Life might not exist on any other planet, but even if it does—even if there is, say, some creature vaguely resembling a paramecium swimming in a pond on some moon halfway across the galaxy—then there, too, it’s just a freak accident. Or as the great molecular biologist Jacques Monod dourly noted in 1971, “The universe was not pregnant with life, nor the biosphere with man.”
But there is a third possibility. In his new book Universe in Creation: A New Understanding of the Big Bang and the Emergence of Life, Roy Gould, an education researcher at the Harvard-Smithsonian Center for Astrophysics, argues that life is neither a miracle nor an aberration, but an inevitability whose emergence is dictated by the laws of nature. He frames his book around a question posed by the physicist John Archibald Wheeler in 1983. “Is the machinery of the universe so set up, and from the very beginning,” Wheeler asked, “that it is guaranteed to produce intelligent life at some long-distant point in its history-to-be?”
Gould answers Wheeler’s hypothetical in the affirmative. To do so, he walks us through the history of the universe, making the case that at each step, the “universe’s major construction projects … laid the groundwork for life.” The result is a fascinating synthesis. You have probably heard, for instance, that the universe is steadily expanding. But as Gould describes, it is not growing outward like a balloon, progressively filling up more space around it. Instead, new “universe” is constantly being created, every moment, in the interstices of space and matter. But the manner in which the universe expands, he argues, happens to be optimal for the emergence of life. For instance, it the universe had expanded more quickly, stars would not have formed; more slowly, and hydrogen—a basic component of water and hence life—would not exist. In either case, you would not be reading this paragraph; therefore, the “universe’s infrastructure guaranteed that things would work out properly.”
Gould artfully describes various other highlights in universal history, like the formation of stars and planets. Many of these moments are majestic and hard to visualize, like when stars explode, ejecting their innards throughout the universe, which then, acting under gravitational forces, coalesce into new stars and planets. He describes how under certain conditions all stars will produce carbon, the basic atom of life (at least as we know it). Hence: the laws of nature produce stars, stars invariably produce carbon, carbon is a necessary constituent of life, and ergo, the laws of nature lead to life.
Sometimes, such arguments carry a whiff of tautology: by definition life could not have emerged in the universe if the universe did not provide the preconditions for it do so. But in the final third of the book, Gould returns to answer Wheeler’s question more directly and persuasively, offering “the chief lines of evidence that life really is written into the universe’s building plan.” He notes, for instance that life appeared very soon after the planet’s birth: there are fossils that are almost 4 billion years old, while the earth has only been around for 4.5 billion years. This rapidity suggests a certain inclination towards life, as does the fact that you can find creatures everywhere on the planet, even in its most inhospitable corners, from the bottom of the oceans to, say, a boiling hot geothermal spring.
Life’s machinery is remarkably stable: The same basic genetic code exists in all living things and has survived for billions of years. Other evidence for his thesis includes convergent evolution, which happens when two species independently evolve some similar function or organ. For instance, fish have developed electrical organs—which allow them to do fun things, ranging from shocking their prey to navigating their environment—on six or more distinct occasions in evolutionary history, as Gould notes, which suggests a certain predictability; creatures tend to evolve the same kinds of adaptations when they are presented with particular environmental challenges.
That is to say, life didn’t waste much time in emerging; it occupies
every nook and cranny of the planet; it has a remarkably stable infrastructure
over time and space; and it sometimes evolves in semi-predictable ways towards
common ends. This might indicate, as Gould says, that it “didn’t merely show
up: life seems to belong here.” Fair enough, but this still leaves open the big
question. Why, and how, did life emerge, in the first instance, at all?
When Gould turns to the origin of life itself, his book leaves
somethings to be desired. He largely neglects to discuss competing theories of
the origin of life. He favors the predominant theory, RNA World—even though one could argue that theory contradicts his central thesis. RNA world is
typically explained like this: There are two main genetic molecules, RNA and
DNA. It’s unlikely that life started with DNA, because DNA needs complex
proteins to help it replicate, but complex proteins are produced by DNA. RNA,
however, is a more versatile molecule. It can move around the cell as a
messenger. It can help build proteins. It can even itself function like a
protein, catalyzing chemical reactions—including the replication of RNA itself. It can serve as blueprint, architect,
and contractor, all at once.
Perhaps, then, one day in a primordial pond filled with organic molecules, an RNA molecule came together with the capacity to replicate itself. That would be one of the most consequential half-seconds in the history of the earth (and potentially, the universe): the moment life began. Evolution would take things from there, leading from that single molecular strand to every creature on earth, all of which share the genetic code.
Gould embraces this theory, writing that “an ancient RNA world would make sense … it might have served to jumpstart life.” Yet, as others have argued, the spontaneous emergence of such a highly complex RNA molecule would also have been profoundly improbable. The late Robert Shapiro, professor of chemistry at New York University and author of Origins: A Skeptic’s Guide to the Creation of Life on Earth, has put this eloquently: “The chances for the spontaneous assembly of a[n RNA] replicator,” he wrote in a 2007 article in Scientific American, “can be compared to those of the gorilla composing, in English, a coherent recipe for the preparation of chili con carne.” The unlikeliness of spontaneous RNA replication, then, seems to contradict Gould’s idea that the universe was programmed to produce life. It brings us back to the possibility that yes, life on earth was simply a bizarre, freak occurrence.
And yet—and here’s where things get interesting—Shapiro actually agreed with Gould’s fundamental thesis. He adhered, however, to an alternative to RNA-world referred to as “metabolism first,” which he thought consistent with this thesis. In this framework, molecules—perhaps fats—aggregated and “self-organized,” as they are apt to do under the laws of nature, forming compartments within which metabolic circuits began to run, well before complex genetic molecules come into being. These early forms of life may not have resembled life at all, but perhaps something intermediate between the living and the non-living. “There’s nothing freaky about life,” Shapiro said in a 2008 talk. “It’s a normal consequence of the laws of the universe.” Gould says nearly the same thing—“life really is written into the behavior of molecules.”
Whichever specific origin of life theory we turn to, the thesis that life is somehow programmed into the universe feels uncomfortable but also attractive. Uncomfortable, because it seems to carry a whiff of creationism: Is this just wishful thinking after all, intelligent design gussied up for the scientifically-minded? It is attractive, however, for the same reason. It means that life is the inevitable, invariant consequence of the laws of physics at work, giving life about as much meaning in the universe as an atheist could in good conscience ask for.
What we want to be true is, of course, irrelevant. The fascinating thing, however, is that Gould’s thesis may very well prove true. If it turns out that life—even the most rudimentary microbial life—is common to the universe, the case, as Gould suggests, is settled. Given the distances humans would have to travel to verify this, it is not something that can easily be proved. But even if there is or ever has been any sort of simple life on Mars—and this is something that could be ascertained in our lifetime—then Shapiro and Gould, although they embrace different theories of the origins of life, are essentially correct.
After all, if life emerged independently on two planets in a single solar system, it is nothing unusual. Indeed, that finding alone would be powerful evidence that life has a tendency to emerge, and is presumably widespread throughout the universe. The origins of life would indeed be found in the laws of nature.
But we can’t make too much of that either. For though any such finding would greatly raise life’s stature in the universe, it would do nothing to elevate that of humanity. Even if we prove that life is a property of physics, we humans would still be creatures of chance—and natural selection. Monod would thus be half-wrong and half-right: the universe would indeed have been pregnant with life, but not with humanity.