Themes
Key
LitCharts assigns a color and icon to each theme in A Short History of Nearly Everything, which you can use to track the themes throughout the work.
Science, Discovery, and Mystery
Writing, Wonder, and Inspiration
Progress, Sexism, and Dogma
Existence, Awe, and Survival
Summary
Analysis
Humans want to think we have a purpose on Earth, but science shows us that sometimes life “just is.” Lichens, for example, live out their existence by simply clinging to rocks, absorbing minerals for food. If Earth’s history were compressed into a single day, life would get going at four a.m. with microbes. It takes until 8:30 p.m. for sea plants and jellyfish to show up. Around 10 p.m., land plants emerge, and around 11 p.m., the dinosaurs turn up, lingering until 11:40 p.m. Humans show up at 11:59 p.m., and they’ve so far been on the scene for just one minute. Bryson suggests that perhaps most life isn’t ambitious because complex organisms tend to go extinct, while simpler ones—like jellyfish—are still around.
Bryson invokes the analogy of life as a single day on Earth to show how late into the day humans come onto the scene and how short in duration our time on this planet has been thus far. Nearly all of Earth’s history—everything up to the last minute of the day—happens before humans exist, meaning that there is a near-infinite amount of scientific information yet to be gleaned about the past. The metaphor also emphasizes the rarity of human existence: our species is a tiny blip on the timeline of Earth’s history, meaning that most life doesn’t evolve into human life.
Themes
In order for marine animals to evolve into land life, creatures have to develop a different internal architecture (including a load-bearing spine) and learn how to consume oxygen from the air instead of water, which is no easy feat. Though we usually imagine our ancestors as fish with legs, or as early amphibians, they’re most likely mites (living on plants) that crawl onto land when plants do. Dead vegetation falls into swampy sediment instead of fully decomposing and releasing carbon dioxide into the air, resulting in much higher oxygen levels that enable land life to rapidly grow larger. Early millipede fossils reveal specimens as large as six feet long.
Bryson wants to stress that the fact that human life evolved at all is astounding, since it required marine life to evolve into land life—which demands a complete restructuring of both the skeleton and respiratory systems. Bryson further emphasizes the marvel of life in general by stressing how much larger everything was when there was more oxygen on Earth. Bryson helps the reader to visualize this so that they can become both fascinated and amazed about the planet we live on.
Themes
Eventually, insects evolve to fly. Early dragonflies are as large as ravens, and plant life is much larger too—ferns alone rise 50 feet high. In 1948, an eccentric Swedish scientist named Erik Jarvik acquires an “Ichthyostega” fossil, which scientists think might be the common ancestor fish for all tetrapods (a category that includes dinosaurs, whales, birds, humans, and fish). Unfortunately, Jarvik locks it away in his office and it doesn’t surface again until after his death in 1998, when scientists realize Jarvik that mis-described it—it’s not, in fact, a tetrapod. Since then, no other viable early tetrapod fossils have been found, so this part of our history remains a mystery.
Bryson shows that despite all the obstacles to scientific knowledge about historical life on Earth that humans face—such as a paucity of evidence—the eccentric personalities of scientists themselves can also slow down scientific discovery, as the case of Jarvik shows. It takes almost 50 years for scientists to realize that his fossil isn’t the one they’re looking for. The complete absence of fossils from crucial periods in the history of life shows that most of the story of evolution still evades scientists.
Themes
Scientists divide land-creature evolution into four “megadynasties.” The first consisted of primitive reptiles, amphibians, and turtles. One branch of these creatures evolves into the earliest “protomammals” (called therapsids) who comprise the second megadynasty. Meanwhile, another branch evolves into dinosaurs, who destroy nearly all the therapsids except for small burrowing mammals about the size of mice. The dinosaurs take over and comprise the third megadynasty, followed by our own “Age of Mammals.” Bryson says one of the strangest features of life is the prevalence of extinction. Over 99.99 percent of all species that have ever existed have gone extinct. The typical life span for complex species before extinction is about four million years, which is about where humans are right now.
Even though the idea of human extinction seems remote to us on a day-to-day basis, it’s actually not—in fact, it’s likely inevitable. Bryson cites the fact that 99.99 percent of species go extinct in order to show the reader how precarious human existence is. In fact, it’s even more precarious today than it’s ever been before, because most species go extinct after they’ve been around for about as long as humans have been around now. Bryson’s aim is to show that extinction is already the likely outcome for our species, so we should not accelerate it by being reckless with human life.
Themes
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Though it seems counterintuitive, extinctions are actually good for life’s evolution—mass extinctions are typically associated with massive leaps forward. For example, darting fish only began to thrive after immobile filter feeders went extinct. Earth has had five mass extinctions in its history (all before the era of dinosaurs), each of which wiped out approximately 70-95 percent of Earth’s species. There were also 12 or so smaller-scale extinction periods, though one of them almost wiped out horses. (Bryson can’t imagine the world without horses.) Figuring out why mass extinctions happen, however, is much more difficult. Scientists speculate that anything from climate change to “catastrophic” solar flares might be responsible for Earth’s mass extinctions.
Mass extinctions provide important clues about evolutionary processes, since they typically drive evolution forward. Despite how important it is to know about prior extinctions in Earth’s history, scientists actually know very little about them—they know that they happened, but they don’t know why. Five of these extinctions have been mass extinctions that wipe out most life on Earth, further stressing how perilous the continued existence of our species is. The fact that we’ve lasted so long is very lucky, especially as we have insufficient knowledge about what triggers mass extinctions in the first place.
Themes
Bryson explains that the KT asteroid impact that wipes out the dinosaurs is enormous. The impact’s force exceeds the power of eight billion atom bombs. The KT impact also happens when Earth is more oxygenated—and therefore more combustible. The asteroid lands in a shallow sea bed made of sulfur, triggering several months of burning acid rain, while debris from the impact blocks out the sun for months, maybe years. Yet curiously, 30 percent of species survive this event, including crocodiles, snakes, turtles, amphibians, and corals. It turns out that the impact kills 90 percent of land animals (including all the large ones) but only 10 percent of sea animals (sparing large sea creatures like sharks).
Though Bryson, thus far, has warned about the dangers of asteroid impacts and emphasized how closely humans come to total annihilation on a daily basis, our existence—paradoxically—also depends upon asteroid impacts. If the KT impact didn’t happen when mammals were very small and dinosaurs were very big, humans likely wouldn’t have evolved at all. Once again, Bryson stresses that our existence is a matter of sheer luck.
Themes
Luckily for humans, the land survivors include our ancestors: tiny, nocturnal, burrowing mammals. With the dinosaurs gone, mammals thrive. Bryson says this historical age sees guinea pigs as large as rhinos, rhinos as large as two-story buildings, and fierce 10-foot-tall carnivorous birds. Unfortunately, too few fossils have been discovered thus far for scientists to paint an accurate picture of the early age of mammals. Similarly, the 300 or so dinosaur fossils discovered in the 19th and 20th centuries capture just a mere glimpse of life in that age. Bryson says that humans feel sure about our status as life’s “dominant species,” but actually, “we are here only because of timely extraterrestrial bangs, and other random flukes.”
Bryson employs colorful descriptions of giant mammals in our ancestral line to peak the reader’s interest and inspire their imagination, reflecting the kind of writing that he thinks will fuel scientific engagement among the general populace. This is particularly pertinent for discussions about the early age of mammals since scientists have little to no evidence about life during this time. Even the discovery of one new fossil would therefore be game-changing for the scientific community. Bryson closes out the chapter by stressing once again that the existence of our species is dependent upon the whims of chance.
Themes
