66 million years ago, the dinosaurs had a horrible day. We all know the story. An asteroid over eleven kilometers long crashed into what is now the Gulf of Mexico and left a geological scar over eighty kilometers in diameter. A planet Earth, as we have never known it, disappeared forever with 75% of its species.
American Riley Black, one of the most recognized voices in modern paleontology, reconstructs in The Last Day of the Dinosaurs (Capitán Swing) not only the last day, but also minute by minute, hour by hour, and million years by million years after the impact of the meteorite, to discover the succession of coincidences that allowed that, right now, wherever you are reading this news, it is you and not a Triceratops.
One fine day 66 million years ago, the Triceratops was enjoying a new day of hegemony on Earth, until an asteroid impacted at a speed of 20 kilometers per second near what is now Chicxulub (Yucatán, Mexico), releasing an energy equivalent to billions of atomic bombs. It was the beginning of a disaster movie impossible to film: a fireball, seismic waves traveling across the planet, a global tsunami, local temperatures instantly rising to thousands of degrees, dust and vaporized material ascending into the atmosphere, only to return as incandescent rain, and fires ravaging entire continents.
-When we watch a disaster movie, we all think about how we would survive, but I don't know if a human, that day, would have any chance -we asked Riley Black.
-The best option would be to start digging and take refuge underground. We know, from current forest fires, that when the air heats up, as it did after the impact, the temperature rises to about 260°C, basically the temperature at which you roast a chicken. You have to get away from that heat, obviously. The first day would be the most critical because, no matter where on the planet you were, the heat was so extreme that everything burned. We also know from forest fires that if you manage to bury yourself about 5 or 10 centimeters underground, the ground acts as a buffer: it's cooler down there. That's how many small organisms survived the disaster. But that would only be the best option to escape the heat. The next challenge would be to escape the cold, the equivalent of a nuclear winter that would last at least three years. You would have to find food, stay warm, and avoid the side effects of ash in the air. Would it be possible to survive? Yes, but extremely difficult.
-Okay, what if we could choose to be an animal?
-I would choose a sparrow. We know from its ancestors that they survived the disaster. You are small, to escape the heat you could take refuge underground, and you keep your body warm because you are warm-blooded. Also, you are herbivorous: on the ground, there are all kinds of seeds that do not germinate and are a source of food. For a long time, it was a mystery why birds were the only dinosaurs that survived. Birds have been around for about 150 million years. It's a pretty impressive record.
In the first hours, the atmosphere was covered in soot and ashes, and the sky darkened. Without sunlight, photosynthesis stops. The global temperature drops sharply. A post-impact winter begins. All ecosystems collapse. In just a few weeks, the planet seems dead. However, microbes, fungi, and cold-resistant plants begin to take advantage of the organic remains. The phenomenon called "fern spike" appears. After the fires, ferns colonize the devastated areas before any other plant. Ecosystems begin to rebuild from the simplest forms. Seeds that evolved to withstand forest fires were also the reason forests regrew.
During the first year, atmospheric dust continued to block the sun. The seas acidified due to acid rain. Coral reefs and many marine species disappeared. But amphibians, turtles, and small mammals were able to survive by hibernating in aquatic refuges or underground burrows. Survival was not a matter of chance, explains Riley, but was favored by certain biological traits: dietary flexibility, low metabolism, and the ability to live in a shelter. "We are not facing a simple catastrophe, but a cosmic reconfiguration of the planet," explains Riley. The asteroid not only destroyed the world of the great saurians. It also sowed the conditions for another type of life to thrive. An inversion of natural hierarchies in which, according to the author, one of the most powerful lessons of Earth's history is found: "Life does not disappear, it transforms." Power shifted from the colossi to the opportunists, and from roars to underground murmurs.
-And what about the idea that if it had fallen 30 seconds earlier or later, we wouldn't be here?
-We know that other asteroids hit Earth before and after that event, but they did not cause mass extinctions. This one did, and it did so, literally, by falling in the worst possible way. If the asteroid had impacted 30 seconds earlier or later, due to Earth's rotation, it would have fallen in a different place, on a different type of rock that may not have contained the compounds that triggered the post-impact winter.
-It could have fallen in the ocean, which would have been devastating for nearby marine creatures, but it would not have caused a global extinction. The fact that it impacted near the coast, and on sulfur-rich rocks, was decisive. We know that if you introduce sulfur compounds into the atmosphere, they reflect sunlight, prevent plants from photosynthesizing, and cause acid rain, among other catastrophic effects. Dinosaurs like T. Rex or Triceratops, which had already been on Earth for over 150 million years, would have continued to exist. If the mass extinction had not occurred, evolution would have taken a different course. Our primate ancestors, who already existed when the meteorite fell, would have lived in a world dominated by giant reptiles, and their evolution would have been very different. Humans probably would never have appeared.
After the first decade, the dust began to dissipate, and the sun reappeared. Terrestrial and marine ecosystems began to show signs of recovery. New ecological niches appear: where there were once giant herbivores and predators, now small mammals, birds, and reptiles thrive. Black describes this stage as the planet's awakening.
-And what does this teach us about our own vulnerability as a species?
-That being big, strong, and fierce is often a disadvantage. And that if you are small, flexible, a generalist, capable of living in many types of climates, and feeding on many different things, you are much more likely to survive. If something like this were to happen again, it would be devastating for millions of people, but as a species, we could survive because we are omnivores, generalists, capable of adapting to many climates and types of food. And we also invent tools, and even tools that make other tools.
After the first million years, there are no non-avian dinosaurs left. The planet is different: less CO?, cooler climates, new vegetation. Mammals begin to diversify and increase in size. The first forests of the Paleogene develop. The impact event, rather than an end, is perceived as a transition.
Although Earth has always survived its crises, the systems that sustain it change radically. In that geological mirror, the author makes us look at the Anthropocene, the current moment, in which humans occupy the place of dominant dinosaurs, altering climates, seas, and atmospheres.
-Are we repeating, on a different scale, that end?
The mass extinction caused by the meteorite happened very, very quickly: within a span of 24 hours to three years. Most life forms went extinct in a geological blink of an eye. What we are doing to the planet is occurring over a much longer period, resembling previous mass extinctions caused by huge volcanic eruptions that released methane, carbon dioxide, and other greenhouse gases. Those had natural and unpredictable geological causes, but what we are doing now can be changed, stopped at any moment if we find a different way to relate to the planet. We are causing changes that are leading many species to extinction at a much faster rate than would occur naturally. But we have a choice: we can acknowledge what is happening and take action. The extinction we are witnessing now is not inevitable.
- What can the meteorite teach us about understanding and solving the current climate crisis?
- It serves as a reminder of how grateful we can be to exist. In terms of our climate crisis, it reminds us that nature is always changing, that we are not separate from nature, and that we will not leave it untouched because we are an active part of the planet, even in the most remote places. And that is a responsibility: to acknowledge our impact and create a future where all can thrive. The lesson is to recognize that we are descendants of the survivors of that extinction.
The Last Day of the Dinosaurs, far from being a tale of catastrophe, is a hymn to cosmic resilience: the certainty that even after the worst devastation, the planet flourishes again. But it is also a moral warning: rebirth is not guaranteed for any particular species. The story of the dinosaurs is not prehistory; it is an elegant premonition of what happens when a form of life believes itself eternal.
- In the book, you mention that if we fail, life will continue, with whom?
- If we fail, we will not leave alone because we interact with many other species. History shows us that life has gone through extreme climate changes before. Sometimes large organisms became smaller to regulate their body temperature. Flowering plants would likely continue to expand. Animals that coexisted with us, like deer, raccoons, and others considered pests, would multiply and start creating new ecosystems. During the early months of the Covid pandemic, we saw a glimpse of this. Highly intelligent species could evolve, such as crows, magpies, dolphins, elephants, with different ways of relating to the planet. In a way, it would be like rewinding the tape: the world would temporarily resemble the beginning of the Pleistocene, when there were mammoths, mastodons, giant sloths, and saber-toothed cats. Right now, we live in a world with less charismatic megafauna, but if we were to disappear, they would reshape ecosystems similarly to how the dinosaurs did. I wish I could be here to see it.