Existence, Awe, and Survival Theme Analysis

In A Short History of Nearly Everything, Bill Bryson argues that life on Earth is essentially a long shot. The slightest differences in cosmic, geological, and biological events throughout Earth’s history would have prevented life from being created at all. Moreover, the perpetually high odds of obliteration (from asteroids, natural disasters, and biological threats) mean that life’s continued presence on Earth is an unimaginable stroke of luck. Yet, despite hanging on a perilous “knife-edge,” humans often recklessly endanger life on Earth. Bryson emphasizes the fragility of our existence to instill a sense of amazement and prompt the reader to question self-destructive activities—like pollution and biological warfare—that humans willfully engage in.

Bryson argues that Earth would not have been able to sustain life had the slightest difference in early history’s celestial events occurred, meaning Earth’s presence as a life-sustaining planet is essentially a cosmic stroke of luck. For example, the formation of an atmosphere containing carbon dioxide at just the right time in Earth’s development as a planet—when Earth was about a third of its current size and the sun was significantly younger and dimmer—created a greenhouse effect, without which “Earth might well have frozen over permanently, and life might have never gotten a toehold.” In other words, Earth happened to be just the right distance from the right-sized star at just the right time in cosmic history for it to sustain life. Similarly, if Earth were a planet without a molten core, there would be no mountains and its surface would likely be smooth and evenly covered in water. Even if life was somehow able to evolve in that environment, it likely wouldn’t evolve into human life (which got started when sea life evolved to crawl out of the sea). The moon was likely created by a massive asteroid impact that sent part of Earth’s crust into orbit around Earth. Without the stabilizing gravitational pull of the moon, Earth would wobble on its axis, drastically affecting its climate and likelihood of sustaining life.

What’s more, Bryson indicates that the likelihood of a meteor striking Earth and obliterating life—just as one did for the dinosaurs 65 million years ago—is so high that the absence of such an impact during the evolution cycle that gave rise to humans is nothing short of a miracle. Scientist Steven Osro suggests that if all the asteroids crossing Earth’s orbit could be lit up and made visible to humans, we’d see “millions upon millions upon millions of nearer randomly moving objects” in space, which are all capable of “colliding with the Earth” and triggering potentially devastating effects. Bryson similarly estimates that approximately 2000 asteroids capable of obliterating life on Earth “regularly cross our orbit,” meaning that the threat of destruction by asteroid impact is very real and ever-present.

Planetary fluctuations on Earth similarly threaten human life, further showing how lucky humans are to have (thus far) avoided annihilation by natural disasters. There are approximately two earthquakes each day on Earth (which scientists understand a little better since realizing Earth’s crust is comprised of a series of tectonic plates floating on molten rock) but there are also “random” “intraplate quakes” capable of global devastation about which scientists know nothing so far, other than that they exist. In addition, Earth’s magnetic field is variable and reversible. In the era of the dinosaurs, it was three times as strong as it is now, and it is currently diminishing. If it diminishes too much, it will no longer protect humans from cosmic radiation, which would also end life as we know it.

Bryson also argues that advances in medicine have also lulled humans into a false sense of security about the perpetual threat of disease to humanity, since we could easily be wiped out by newly evolving viruses, especially in today’s globalized world in which humans’ travel lifestyles “invite epidemics.” Bryson argues that despite the cosmic, geological, and biological risks that all life on Earth faces on a daily basis, some of the most damaging threats to its many life forms are actually caused by humans ourselves. As far as we know, humans have been responsible for more extinctions than any other species on Earth. Between 10,000 and 20,000 years ago, human migration destroyed 75 percent of North and South America’s large animals and 95 percent of Australia’s. Today, scientists estimate that human-caused extinction “may be running as much as 120,000 times” higher than any damage we have caused in the past. Notwithstanding the threat to other species, ongoing mass extinction could also upset the food chain that sustains human life. 

Bryson also argues that human-generated pollution increasingly threatens the delicate atmospheric balance that sustains life on Earth. For example, American engineer Thomas Midgley’s 20th-century inventions of chlorofluorocarbons (CFCs)—which were mass-produced in “everything from car air conditioners to deodorant sprays”—resulted in humans unwittingly burning a hole in Earth’s ozone layer, which deflects cosmic radiation that would otherwise wipe out most life on Earth. Additionally, Bryson cites several other examples of human-generated destruction, including microbial warfare (which could result in the rise of antibiotic-resistant bacteria) and atomic warfare (which could destroy all life on Earth except some insects) to show how often we wreak havoc on our already slim chances of survival.

Bryson emphasizes the delicate balance in which life on Earth hangs to show what a miracle it is that life exists at all—and that humans, in particular, exist as part of it. Bryson’s aim is to foster amazement at our existence, awe for the planet we live on, and caution against the many self-destructive activities that humans carelessly engage in. So far, Bryson concludes, humans have had a lot of “lucky breaks,” but it will take a lot more to keep us here in the future.