We Must Live Together Or Perish

An essay I wrote years ago but never published

The Earth and the Moon from about 3.9 million miles away (NASA/JPL)

Before I go on vacation I’m sharing a short essay I wrote in 2016 that was intended to be the prologue to a book on the long-term future of humanity. I wasn’t expecting—and haven’t had time to write meaningfully about—the short-lived rebellion against Vladimir Putin, but civil conflict in a nuclear power should be a reminder of the fragility of human civilization.

“What happens here on Earth, in this century, could conceivably make the difference between a near eternity filled with ever more complex and subtle forms of life and one filled with nothing but base matter.”—Martin Rees¹

Our universe came into being roughly 13.8 billion years ago. For several hundred thousand years, it was too hot even for atoms to form, let alone for life to develop. There was no life in the universe. Nothing had a thought, intention, or feeling.

We don’t know why the universe is the way it is. But life would probably not have been possible if any one of the basic features of our universe were slightly different than they are. If either the initial distribution of matter, the initial entropy, or the fundamental forces—strong, weak, electromagnetic, and gravitational—were much different, it would have been hard for life to develop. The universe would have collapsed or expanded too quickly; it would have been too featureless or too turbulent for sustained chemical interaction; it wouldn’t have had the variety of elements necessary for complex chemistry; or there wouldn’t have been enough free energy to support life anyway. Our universe seems to have precisely the characteristics necessary to make life possible.

Life did develop in at least one place in the universe. Some time after the universe cooled, naturally occurring molecules began to catalyze the production of new copies of themselves. They drew on pent up energy in the environment by lowering the barriers to certain chemical reactions, in roughly the way we can draw on the potential energy stored in a reservoir by opening the gates and letting the water flow. More complex versions of this cycle developed as it gradually varied over the course of many generations. The suites of molecules involved in this process generated—through changing conditions and over billions of years—an unbroken chain of descendants that produced the diversity of life on Earth today.

Life is a marvel of thermodynamics. Living things are islands of order in a universe that tends to chaos. The second law of thermodynamics requires that the entropy of a closed system—a measure of the randomness with which its parts are arranged—increases until it reaches thermal equilibrium. But living things can remain out of equilibrium with their environment almost indefinitely; as they grow and develop their internal entropy can even decrease. A seed can catalyze the atoms in soil and air can organize themselves into a tree.

Resisting the natural tendency of things to fall into disorder takes work. Life can remain out of equilibrium with its environment only by drawing on and dissipating more energy than other processes. Life on Earth depends on the enormous flow of energy from the sun to power the processes by which they grow and maintain their structure. Living things are able to maintain their internal order without violating the second law of thermodynamics only by increasing entropy outside of themselves. They draw on the flow of energy to effectively pull order out of their environment; they are in this way like standing eddies in the natural flow of energy, isolated pockets in which matter becomes more organized rather than less. But life can cheat entropy only locally and only temporarily. When living organisms die—and the systems with which they maintain their structure cease to function—they can come apart quickly. Eventually, the flow of energy will cease; the stars will burn out and life in the universe will come to an end.

Most of the matter in the universe is inert and lifeless. Even if there were life on every Earth-like planet, living matter would account for just around one-billionth of one-billionth of all the matter in the universe.² It may be even less. The only living things we’ve so far identified in the universe inhabit a thin film on the surface of this one planet.

Life seems to have developed on Earth not long after the planet formed. The discovery in South Africa of what appear to be filamentous microfossils in 3.4-billion-year-old rocks indicates that life had already developed within in the first 1.1 billion years of the planet’s 4.5-billion-year history. It took another 1.2 billion years for some of those organisms to develop the internal cell structures like nuclei and mitochondria shared by virtually all of Earth’s complex multicellular life. That it took so long for these structures to evolve—and that they seem to have developed only once in Earth’s history—suggests that complex life like ours might develop only rarely.

Some branches of life on Earth eventually began to develop the ability to think and learn. Instead of following relatively simple, fixed programs of behavior, they developed the ability to learn from experience, work out new strategies, and plan for the future. We humans in particular have come up with sophisticated ways of understanding and controlling our environment. We’ve developed philosophy, mathematics, science, history, and literature. Nature has produced in us beings capable of reflecting on nature. Seen through our eyes the universe has meaning.

In the 200,000 years since modern humans emerged, we have come to dominate practically every ecosystem on Earth. We have changed the composition of the planet’s atmosphere and its oceans. We’ve even started to explore the space beyond our world and to build machines that rival or surpass our own abilities. The potential of human civilization to explore and create is practically limitless.

The same process through which intelligence evolved on Earth may occur on other planets in other solar systems. Simple organisms may be relatively common throughout. We may even discover life evolved independently somewhere else within our own solar system. But species as intelligent as humans are likely to be much less common. Human intelligence evolved only after the Earth’s environment was relatively stable for around four billion years. Life on Earth had to survive at least five separate mass extinction events before humans arrived. By the time humans did appear, the Earth’s habitable period was already about 70% over. In another 1.5 billion years, the sun will grow larger and brighter, boiling off the Earth’s atmosphere and sterilizing its surface. On other, similar planets, intelligent life might not have as much time to develop as it did here.

If there are other technologically advanced civilizations among the more than 100 billion stars in our galaxy, we have yet to see any clear sign of them. It may be that technologically advanced civilizations do not spread widely among the stars or that they do not produce signals we can readily detect across great distances. But it may also be that species as intelligent as we are appear only very rarely or do not survive for long when they do. As far as we know, we’re alone in the universe.

Our own existence may be more tenuous than we realize. The 200,000 years modern humans have lived is less than 0.01% of the 3.4 billion years life has existed on Earth. We certainly can’t conclude from humanity’s short history that we will survive indefinitely. In spite of our success as a species, humans may actually be at greater risk of extinction than at any other time in history. While we remain confined to the surface of a single planet, we are vulnerable to a range of global catastrophes. In addition to the threat posed by natural disasters like asteroid impacts, there’s a growing danger that we ourselves could cause a global catastrophe. The same technology that insulates most humans from the day-to-day struggle to survive, gives us the collective power to destroy ourselves. We now have enough nuclear weapons in our arsenals to produce the equivalent of a major asteroid strike. We’re already causing a sixth global mass extinction event. We’ve altered the Earth’s climate in ways that will have serious lasting consequences. As our technology advances, our power to harm ourselves will only grow.

We’re now the greatest threat to our own survival. We have the technical ability to overcome practically every challenge we face, if we work together. But our ability to govern ourselves has not kept pace with our ability to harm ourselves. If we turn our power on one another now—or simply fail to work together effectively to address our common problems—the human race may not survive.

We must not squander the temporary miracle of our existence. We do not have to resolve all our differences or agree on a single vision. But we do need to take collective action to ensure the long-term survival and prosperity of the human race. One reason we haven’t seen signs of other intelligent life in the universe is that civilizations as advanced as ours may tend to destroy themselves. Surviving our transition to a species that has the ability to remake both our planet and ourselves may be the greatest challenge we’ll ever face. If we fail to rise to it, there may not be anyone to mourn our passing.

I’ll be on vacation until the middle of July. I won’t have time before I go to write about the recent events in Russia—which appear to have weakened Putin’s hold on power and further undermined Russia’s ability to fight in Ukraine—but I am contributing the Swift Centre’s live forecasts of the events as they continue to develop. In any case, I’ll have more to say in a few weeks.

1. Martin J. Rees, Our Final Hour (Basic Books, 2004): 8.

2. Alan Lightman, “Is Life Special Just Because It’s Rare?” Nautilus (October 25, 2015).