Since Berner and Canfield’s original study appeared, dozens of papers have explored the connection between increased oxygen content and giantism, and the growing consensus is that higher oxygen concentration would support larger body plans in reptiles and insects. And the increase in atmospheric pressure that accompanies 35 percent oxygen levels would even alter the aerodynamics enough to allow Meganeura to take flight.
Where did all that oxygen come from? From the plants, of course. First, the plants invented the photosynthetic engine that created an oxygen-rich atmosphere billions of years ago. But at some point near the end of the Devonian age, the plants evolved the ability to generate a sturdy molecule called lignin that gave them newfound structural support, allowing them to grow to sizes never seen before on Earth. Larger plants alone might have led to an oxygen increase, but lignin may have also had a more indirect role in the spike. One popular but unproven theory argues that lignin confounded the microbial recyclers responsible for the decomposition of organic matter. Plants absorb carbon dioxide and produce oxygen through photosynthesis; decomposition plays that tape backward, as bacteria and other animals use up oxygen in breaking down the plant debris, releasing carbon dioxide in the process. Lignin may have disrupted that cycle, because the recyclers had not yet evolved the capacity to break down the molecule, creating what the paleoclimatologist David Beerling calls an episode of “global indigestion.” With the decomposers handicapped by lignin’s novelty, immense stockpiles of undecomposed biomass filled the swamplands and the forest floor, and the oxygen levels climbed even higher. Oxygen would not return to the 21 percent plateau until the microbes cracked the lignin code, millions of years later.
But the debris accumulated during the age of Meganeura did not disappear from the geological record. It simply went underground. When it ultimately resurfaced, it would transform human history every bit as dramatically as it transformed natural history the first time around.
THIS IS WHERE it is important to pause for a second and contemplate the story in its full scope. Two billion years ago, the cyanobacteria concoct a metabolic strategy that envelops the planet with oxygen. By 300 million B.C., the strategy has proven to be so successful that the Earth is literally overwhelmed with vegetation, and oxygen levels reach unprecedented heights, before stabilizing again. A long parade of events follows: dinosaurs go extinct, mammals rise, continents separate, Homo sapiens evolves, language appears, agriculture blooms. And then Joseph Priestley sits in a room in Leeds and watches a plant grow in a glass, and grasps—for the first time in recorded history, as far as we know—the original breakthrough that made aerobic life possible in the first place.
That sounds like a story of genius and epiphany—a billion years of evolution and then one guy figures it all out!—but we know that framing the story that way misses the complexity of what actually happens when great ideas come to light. We know that the mountain grows in complicated, layered ways, that Priestley was positioned to see the problem of air for many reasons: his brain and biography, his method, the technology of the day, the information networks, the scientific paradigm. But emphasizing those interacting forces—the ecosystems view of cultural achievement—doesn’t take anything away from the essential magic of linking these two breakthroughs across the immense span of evolutionary time: the original invention of air, and our human understanding of the process that made that invention possible.
But there is another subterranean link that connects Priestley and the ancient cyanobacteria. All that debris that piled up during the explosion of oxygen 300 million years ago was literally lying beneath his feet as he performed his Leeds experiments, in the form the Yorkshire coal measures, part of the extensive Carboniferous layer that runs throughout northern England. The coal measures are a geological anomaly, one of the most extensive stockpiles of Carboniferous rocks ever discovered on the planet. Most of the coal measures lie in shallow beds just below the surface, though in some places they break out into open air. (Carboniferous limestone out-croppings border the peaks of the Pennine mountain range.) The disproportionate amount of nonbiodegraded organic matter trapped in the Carboniferous layer makes it an unparalleled source of fuel. Even today, 90 percent of the world’s supply of coal dates back to the Carboniferous.
Britain turned out to be blessed with two happy accidents of geology: it had an unusually large stockpile of Carboniferous fuel, and the stockpile’s shallow location made it unusually accessible. (Hence the old saying about Britain being an “island of coal.”) Those Carboniferous rocks are central to the story of why industrialization happened in England first (and northern England, more precisely). Yes, Britain had a technical and entrepreneurial culture that helped it exploit all that stored energy, but without the coal measures themselves, it’s entirely likely that the Industrial Revolution would have originated somewhere else.
This is a recurring theme of human history: major advances in civilization are almost invariably triggered by dramatic increases in the flow of energy through society. The birth of agriculture enabled humans to stockpile energy in the form of domesticated plants and livestock, thus enabling the larger population centers that evolved into the first cities. Empires became possible thanks to innovations that captured the energy required to move armies and government officials across large distances, via the muscular energy of horses or the harnessed wind power of ships. Industrialization took the stored energy of Carboniferous rocks and combined it with ingenious new technology that exploited that energy in countless ways. The result of that new energy influx was a nation utterly transformed in little more than a century: a tremendous increase in wealth and innovation, a radical restructuring of the relationship between town and country, and a whole new way of life—industrial labor—with all the terror and trauma that entailed.
Seeing human history as a series of intensifying energy flows is one way around the classic opposition between the Great Men and Collectivist visions of history. You can tell the history of the world through the lives of individuals, or groups of individuals, and part of that explanation is no doubt true. But you can also tell that story with the humans in a supporting role, not the lead. You can tell it as the story of flows of energy: growing, subsiding, being captured, being released. Think of those flows as a vast, surging ocean, and the individual human lives of history crowded on a sailboat in that turbulent water. The humans can still steer their vessel, and exploit the waves and wind that happen to be pushing in the direction they wish to go. But the humans are largely subservient to the conditions set by those oceanic forces. If the pioneering industrialists in England hadn’t hit upon the strategy of using coal to power mechanized labor, there is little doubt that some other culture would have stumbled across the same idea in the next century. But if the Carboniferous age had played out differently—no oxygen spike, no giants, no planetary indigestion—the history of modern human civilization would be radically transformed, because the dominant source of energy that powered the first wave of industrialization around the world wouldn’t exist.
THERE IS A MORE speculative question here that connects us back to Priestley via another angle: To what extent do order-of-magnitude changes in energy flows affect the creation of new ideas? The anecdotal evidence would seem to suggest at least a correlation between the two: in the long sweep of history, intellectually and technologically dynamic societies tend to burn more fuel than their contemporaries. But the causal link between the flow of energy and the flow of ideas may also be more indirect. Thus far, radical increases in energy have led, almost without exception, to two long-term trends: an overall increase in wealth, and an increase in social stratification. (Most people improve their standards of living eventually, but the elites benefit disproportionately.) Those two factors growing in sync invariably produce at least one subsidiary lifestyle trend: more leisure time. And in Priestley’s age at least, leisure time was where ideas happened. You can’t dabble in scientific experiments when you’ve got to use all your cogniti
ve resources just to put food on the table, or when you don’t even have a table to put the food on. Priestley was a professional minister and educator, in that he was paid directly for those labors, but in some fundamental sense he was an amateur scientist, particularly through the first two decades of his life. Like most of his Enlightenment-era peers, he was a hobbyist where science was concerned.
The price of leisure time is ultimately paid in the currency of energy. Imagine Joseph Priestley transported back to the Dark Ages, as a village priest with a contrarian edge. Even if you could somehow magically implant in his brain all his personal knowledge of chemistry circa 1771, it’s unlikely that he would have ever run the mint experiment, for the simple reason that the mint experiment took months to explore and tweak and contemplate, and only a tiny fraction of the population had that kind of spare time in those energy-poor centuries. You don’t have time for hobbies when you’re living hand to mouth. (Had he been a monk or a prince, things might have been different, because the monks and the princes had leisure time.) We tend to think of money encouraging innovation because it functions as an incentive, and indeed one of the legacies of the coal-powered economic revolution of the eighteenth century is that it created a scientific-industrial marketplace where good ideas could be rewarded with immense fortunes. But accumulated wealth played almost the opposite role in most Enlightenment-era science: it allowed people like Joseph Priestley to pursue scientific breakthroughs without the promise of financial reward. And the lack of a monetary incentive made it easier for Priestley and the Honest Whigs to share their ideas as freely as they did.
So when we attempt to answer the question of why scientific revolutions happen—why Joseph Priestley should have hit upon the secret of where breathable air comes from, and in doing so unleash a new way of thinking about the system of life on the planet—the long zoom perspective necessarily widens beyond the immediate details of biography, past the cultural trends and technological developments, all the way out to the longue durée of the carbon cycle. This should be true of almost all important historical events, because energy flows are such a crucial factor in the development of human societies. But there is a beautiful symmetry in imagining Priestley’s intellectual labor in this light, because he was discovering the very process that, 300 million years before, had set in motion a chain of events that ultimately afforded him the leisure time to make the discovery in the first place. The mountain of scientific understanding grew higher in part because it was sitting on a island of coal.
There is a fearful symmetry lurking in this vista, too. In the following two decades, Priestley’s life would grow even more intertwined with the ancient biomass trapped in those Carboniferous-era coal deposits. That unleashed energy would propel him into the second great intellectual collaboration of his career. It would also nearly take his life.
THE LUNAR MEN
CHAPTER FOUR
The Wild Gas
July 1791
Birmingham
FOUR WEEKS AFTER FRANKLIN SPENT HIS EMOTIONAL final day in London with Priestley, British soldiers set off from Boston to arrest John Hancock and Samuel Adams, triggering the famous ride of Paul Revere, the “shot heard around the world,” and the astonishing retreat of the redcoats. Franklin was still in the mid-Atlantic at that point, but when he finally set foot in Philadelphia, he quickly penned a letter to Priestley with his take on the news:
You will have heard before this reaches you, of a march stolen by the regulars into the country by night, and of their expedition back again. They retreated 20 miles in [6] hours.
The Governor had called the Assembly to propose Lord North’s pacific plan; but before the time of their meeting, began cutting of throats; You know it was said he carried the sword in one hand, and the olive branch in the other; and it seems he chose to give them a taste of the sword first. . . .
All America is exasperated by his conduct, and more firmly united than ever. The breach between the two countries is grown wider, and in danger of becoming irreparable.
I had a passage of six weeks; the weather constantly so moderate that a London wherry might have accompanied us all the way. I got home in the evening, and the next morning was unanimously chosen by the Assembly a delegate to the Congress, now sitting.
The “transitory” world of politics had once again trumped the “timeless” world of science. Franklin only had room for a brief but provocative allusion at the end of his letter. “In coming over I made a valuable philosophical discovery,” he wrote, “which I shall communicate to you, when I can get a little time. At present am extremely hurried.”
That valuable philosophical discovery was most likely the “gulph stream.” We know Franklin had taken his water temperature measurements during that 1775 voyage, and a few days after his initial note to Priestley from Philadelphia, he began writing a new letter, recounting his involvement in the packet-ship mystery as Postmaster General. But the letter was never completed (the draft is in the Library of Congress now), and the next few missives he sent Priestley dealt almost exclusively with the state of the war and Franklin’s immersion in revolutionary politics.
In early 1776, Priestley wrote Franklin:
I lament this unhappy war, as on more serious accounts, so not a little that it renders my correspondence with you so precarious. I have had three letters from you, and have written as often; but the last, by Mr. Temple, I have been informed he could not take. What is become of it I cannot tell.
He then launched back into the world of science, mentioning his recently published Observations on Air, which he was including with the letter, and describing his latest round of experiments, lately focused on the circulation of blood. In the final paragraphs, he wrote:
In one of your letters you mention your having made a valuable discovery on your passage to America, and promise to write me a particular account of it. If you ever did this, the letter has miscarried, for which I shall be sorry and the more so as I now almost despair of hearing from you any more till these troubles be settled.
There is no evidence that Franklin ever managed to relay his “valuable discovery,” despite Priestley’s reminders. It was a pattern that would play out through the rest of their correspondence: Franklin obsessed with the volatile state of the Revolution, unable to turn his mind back to the timeless pursuits of natural philosophy; Priestley offering support for the American cause, but then trying to shift the conversation back to the laboratory. “Though you are so much engaged in affairs of more consequence, I know it will give you some pleasure to be informed that I have been exceedingly successful in the prosecution of my experiments since the publication of my last volume,” Priestley began a typical letter from late 1779. The two countries that Franklin had considered home were at war with each other, and the side he was supporting was losing. Who had time for letters about the “gulph stream” in such a context? Franklin, the world’s most celebrated scientist-statesman, had, at the end of his life, become merely a statesman.
Franklin clearly grieved the loss of his natural philosophy, and in an extraordinary letter written from Passy, outside Paris, in 1782, he wrapped all that intellectual regret into a withering, near-misanthropic attack on his fellow men. Franklin begins with a homily to the importance of leisure time in scientific discovery: “I should rejoice much if I could once more recover the Leisure to search with you into the Works of Nature.” But then, before the sentence can barely come to an end, he switches into a dyspeptic political mode, dividing the world again into the timeless and the transitory: “I mean the inanimate, not the animate or moral Part of them. The more I discover’d of the former, the more I admir’d them; the more I know of the latter, the more I am disgusted with them.” And then Franklin launches into a sentence whose sprawling assault on humanity is matched only by its equally sprawling syntax:
Men I find to be a Sort of Beings very badly constructed, as they are generally more easily provok’d than reconcil’d, more dispos’d to do Mischief to each
other than to make Reparation, much more easily deceiv’d than undeceiv’d, and having more Pride & even Pleasure in killing than in begetting one another, for without a Blush they assemble in great Armies at Noon Day to destroy, and when they have kill’d as many as they can, they exaggerate the Number to augment the fancied Glory; but they creep into Corners or cover themselves with the Darkness of Night, when they mean to beget, as being asham’d of a virtuous Action.
Franklin the satirist appears next: “A virtuous Action it would be, and a vicious one the killing of them, if the Species were really worth producing or preserving; but of this I begin to doubt.” Mindful of his much more magnanimous reader, he artfully draws the argument back to Priestley’s ministry and his experiments, with a dark twist of the knife at the end, borrowed from Swift:
I know you have no such Doubts, because in your Zeal for their Welfare, you are taking a great deal of Pains to save their Souls. Perhaps as you grow older you may look upon this as a hopeless Project, or an idle Amusement, repent of having murdered in mephitic Air so many honest harmless Mice, and wish that to prevent Mischief you had used Boys and Girls instead of them.
The Invention of Air Page 10
