Narrator: In the year 1621, a remarkable event unfolded on London's River Thames. A Dutch inventor named Cornelius Drebbel, working for King James I, submerged a wooden vessel and rowed it underwater for three hours, traveling a distance of ten miles from Westminster to Greenwich. The twelve oarsmen inside should have suffocated, yet they remained perfectly fine. Drebbel’s secret was a mysterious “liquor” he had bottled, which, when released, could refresh the stale air and, as one observer put it, restore its “vital parts.” Drebbel had, in essence, bottled life itself.

This “vital part” of the air, the secret ingredient that sustained Drebbel’s crew, is the subject of Nick Lane’s book, Oxygen: The Molecule That Made the World. Lane reveals that this seemingly simple molecule is far more than just the air we breathe. It is a paradoxical force of nature, an elixir of life that fuels our existence, but also a deadly poison that drives aging and death. The story of oxygen is the story of our planet, our evolution, and the profound, often violent, trade-offs that govern all life on Earth.

Narrator: Oxygen’s identity is fundamentally contradictory. It is both essential for complex life and a potent, dangerous toxin. This duality was recognized almost from the moment of its discovery. In the 18th century, the scientist Joseph Priestley was one of the first to isolate the gas. He famously breathed it, noting how his breast felt “peculiarly light and easy for some time afterwards.” He even mused that, in time, this “pure air may become a fashionable article in luxury.”

Yet, Priestley also possessed a chilling foresight. He observed how a candle burned out much faster and more violently in pure oxygen than in common air. This led him to a profound conclusion about life itself. He wrote, “we might, as may be said, live out too fast and the animal powers be too soon exhausted in this pure kind of air.” He intuited that the very element that invigorated life could also accelerate its demise. This is the central paradox of oxygen. The high-energy reactions it enables, which power our bodies, also produce destructive byproducts. This slow, internal combustion, this "living out too fast," is now understood as a key driver of aging and disease, placing all oxygen-breathing life in a delicate and dangerous pact with the molecule that sustains it.

Narrator: For the first billion and a half years of life on Earth, the world was an alien planet, devoid of oxygen. The atmosphere was a mix of nitrogen and carbon dioxide, and life consisted of single-celled anaerobic microbes that thrived in this oxygen-free environment. Then, around 2.5 billion years ago, a new type of bacteria evolved: cyanobacteria. They developed a revolutionary new trick called photosynthesis, using sunlight to split water and create energy. But this process had a waste product, a gas that was lethally toxic to almost every other organism on the planet: oxygen.

What followed was what biologist Lynn Margulis termed the "oxygen holocaust." As cyanobacteria flourished, they pumped this poisonous gas into the oceans and atmosphere. For the planet's anaerobic inhabitants, it was an apocalypse. Oxygen destroyed their vital proteins and membranes, wiping out entire ecosystems of microbes. This event was, as Margulis stated, “by far the greatest crisis the earth has ever endured.” Yet, from this mass extinction, a new world order emerged. Life was forced to adapt. Organisms evolved new defenses against oxygen’s toxicity and, eventually, learned to harness its incredible power. This cataclysmic pollution event didn't just kill off the old world; it paved the way for the evolution of all complex life, including animals, that would come to depend on the very poison that started it all.

Narrator: The amount of oxygen in the atmosphere has not been constant throughout Earth’s history, and these fluctuations have had dramatic consequences for the scale of life. Around 300 million years ago, during the Carboniferous period, atmospheric oxygen levels are believed to have soared to as high as 35%, compared to our 21% today. This oxygen-rich environment created a world of giants.

In 1979, miners in Bolsover, England, discovered the fossil of a dragonfly with a wingspan of nearly two feet. This was not an anomaly. The Carboniferous period was home to insects of terrifying proportions, including griffinflies like Meganeura with wingspans of up to 75 centimeters, giant spiders, and millipedes the size of a car. Scientists believe this gigantism was made possible by the super-oxygenated air. Insects breathe through a network of tiny tubes called tracheae, which passively diffuse oxygen to their tissues. In today’s atmosphere, the size of an insect is limited by how efficiently oxygen can travel through these tubes. But in the high-octane air of the Carboniferous, diffusion was far more efficient, removing this constraint and allowing insects to evolve to monstrous sizes. This period serves as a vivid illustration of how the planet's atmospheric chemistry directly shapes the physical possibilities of life.

Narrator: The destructive power of oxygen is not just a historical footnote; it is an ongoing process inside every cell of our bodies. The same mechanism that makes oxygen toxic is shared by another lethal force: radiation. This connection was tragically illustrated by the story of the "Radium Girls" in the 1920s. These young women were employed to paint watch dials with glow-in-the-dark radium paint. To get a fine point on their brushes, they were instructed to lick the tips, ingesting small amounts of radium each time.

Within years, they began to suffer from horrific ailments. Their teeth fell out, their jaws disintegrated, and many died from aggressive cancers. The radium they had ingested was bombarding their tissues with radiation, creating highly reactive molecules called free radicals. These radicals are like molecular vandals, tearing through cells, damaging DNA, and causing chaos. Nick Lane explains that this is precisely what oxygen does, just on a slower timescale. Through normal metabolism, a small percentage of the oxygen we breathe is converted into the very same types of free radicals. This means that breathing itself is a slow-motion form of radiation poisoning. The life-giving process of respiration is simultaneously a continuous, low-grade assault on our own bodies, linking the act of living to the process of decay.

Narrator: If living creates damage, why doesn't evolution simply create perfect repair mechanisms to make us live forever? The answer lies in a fundamental trade-off between reproduction and maintenance. This is explained by the "disposable soma" theory of aging. From an evolutionary perspective, an organism is just a vehicle for its genes. The primary goal is to pass those genes on to the next generation.

Energy is finite, so an organism must allocate its resources. It can invest energy in building a robust, long-lasting body—the "soma"—or it can invest that energy in reproducing quickly and often. Evolution has overwhelmingly favored the latter. There is little evolutionary benefit to maintaining the body in perfect condition long after the peak reproductive years have passed. It is more efficient to build a body that is "good enough" to survive, reproduce, and then let it decline. The cellular damage caused by oxygen's free radicals is a key part of this planned obsolescence. Our bodies have antioxidant defenses and repair systems, but they are not perfect. They are just good enough to get us through our reproductive phase. Aging, therefore, is not a disease but an evolutionary strategy—the inevitable price paid for the privilege of passing on our genes.

Narrator: The single most important takeaway from Nick Lane’s Oxygen is that life is not a gentle, harmonious process, but a high-stakes, energetic conflict with its own environment. Oxygen is the ultimate protagonist in this drama—a molecule that offered life unimaginable power at a terrible cost. It drove mass extinctions, enabled the rise of giants, and now dictates the pace of our own aging from within our cells.

This reframes our entire understanding of health and disease. We are not simply fighting external threats; we are managing an internal, life-long negotiation with the very element that gives us breath. The challenge, then, is not to conquer or eliminate the "dangers" of oxygen with miracle cures, but to understand and respect the profound, 4-billion-year-old evolutionary balancing act that allows us to exist at all. How can we live better with this beautiful, terrifying molecule? That is the question oxygen asks of us all.