Which Pests Shall Inherit The Earth? – Defector

11:25 AM EST on February 27, 2025This week we’re running a small package of essays on the topic of nuisances. Why? That’s an annoying question.Marauding asteroids. Lurking pandemics. Climate tipping points. There has never been a better time to contemplate our own extinction. But once humans are old news, who’s up next? Which animal would succeed us if we were to suddenly vanish?It is a thought experiment played out endlessly on Reddit threads, Quora forums, and presumably in real life, assuming your friends are morbid enough. Other intelligent species—octopuses, primates, or dolphins—are commonly floated as our inheritors. But my hunch is that those most primed to seize the throne are the ones already making an open play for it on the sidelines. In simpler terms: the best pests. I see three clear frontrunners: rats, raccoons, and gulls. These three competitors demonstrate intelligence, cosmopolitan distribution, an aptitude for survival, and near-human levels of cheeky boldness. They are already eating our lunch—both metaphorically and literally, in some cases. To confirm or refute this hypothesis, I asked smart people with expertise on rats, raccoons, gulls, and evolutionary transitions to vet my candidates—as well as the premise of the thought experiment. RatsIt’s theirs to lose. Rats are adaptive geniuses that have followed humans all around the world, much to our chagrin. Kelly Lambert, a professor of behavioral neuroscience at the University of Richmond who studies rats and raccoons, describes them as “the planet’s most successful mammals” in her book The Lab Rat Chronicles.Wild rats are “just ferocious and tough,” she told me. “I don’t know if our lab rats would survive too long out there, but the wild rats and the urban rats will just find food, chew through and create new habitats, and survive wherever.”Lambert noted that rats are fast learners. She has taught them to drive little rat-operated vehicles in her laboratory, perhaps giving them an edge in a Mad Max scenario. “That’s a great example of flexibility—to learn something so different from their ancestors, or any predispositions they have,” she said.Rats have another major advantage: They are efficient repopulators. Rats are ready to mate at around 10 weeks old, and they can pump out as many as 100 pups a year. This reproductive superpower not only helps them proliferate; it also means they are quicker as a species to adapt to new and diverse environments than larger mammals, due to their short generation times. We owe our own existence partly to this dynamic: Small mammals flourished in the wake of the dinosaurs’ extinction because they could produce new generations quickly and outcompete slower breeders.“Being big is hard,” said Steve Brusatte, a paleontologist at the University of Edinburgh and the author of The Rise and Reign of the Mammals, in an email. “It requires a lot of energy, you need to eat a lot of food, you need quite a long time to grow from a baby to an adult, and usually your population sizes are pretty small compared to the smaller animals, and all of this makes big things susceptible during cataclysms.”Brusatte noted that smaller animals often rapidly increase in size after larger animals are wiped out by extinctions. If humans were to go extinct, rats could potentially get swole and sprout new giant lineages. Madeleine Goumas, who studied urban gulls for her PhD at the University of Exeter, sees this transition as a key step toward world rat domination. “Rats seem like a good bet seeing as they are already just about everywhere (helped by humans of course) but they would have to grow in size before they were truly dominant over other animals such as foxes, which would suddenly have an even more abundant food supply,” Goumas said in an email.So the future may well be run by colossal intelligent rats that drive cars, or spaceships. “I’ll think I know all that a rat can do, and they come up with something different,” Lambert said. “They’re just brilliant. I cannot imagine all the ways a rat can respond the way a rat can with my human brain.” RaccoonsThe dark horse. These charismatic “trash pandas” would need some exceptional circumstances to get in the door, but they could fully exploit any opening if given the chance. Lambert noted that the wily procyonids are rarely studied in labs because these clever escape artists seem to find a way out of, or into, anything. “If there’s something hard to find, like a resource, or if there’s just something that they can stumble upon out of curiosity, they’re likely to find it,” she said. “I would put humans more in that category, too. They’re very inquisitive and in an exploration mode: What does this taste like? What is this? They’re constantly investigating, as if just to fulfill their curiosity.”But while their adventurous spirit could be a benefit in some circumstances, it also comes at a cost. “Their curiosity gets them into trouble,” Lambert noted. “A rat is very cautious about anything new. It’s hard to poison them because they’re suspicious of new food in a new place.” Raccoons, in contrast, are not as “inhibited,” she said. As a consequence, they usually survive for just two to three years in the wild before meeting with fatal accidents, though in captivity they can live for more than 20 years.Raccoons also invest a lot more parental effort into a smaller number of offspring, relative to super-breeders like rats. This strategy clearly has its advantages—it has worked for humans, so far—but it could be a liability if human extinction set off an evolutionary race to occupy the vast niche carved out by our civilization.That said, in the right conditions, the characteristic inquisitiveness and bravado of raccoons could lead them to interesting places in a post-human world. Rats and raccoons make for “an interesting matchup,” Lambert said. “I’m not sure where I would put my money.”GullsConstitutionally ineligible. While gulls are brainy and bold, it turns out they are not ideally suited to world-domination material—and they’re probably fine with that. “I don’t see gulls dominating,” said Goumas, the gull expert. “As ground-nesting birds, they would likely take a big hit from the larger abundance of rats and other ground predators that would be able to live without humans being around.”Threats to ground-nesting animals are nothing new—small predators, such as snakes and mammals, may have occasionally snatched dinosaur eggs or young hatchings. Gulls that managed to avoid nest raids “would probably be quite happy with the abundance of fish and less-polluted beaches that an absence of humans would bring,” Goumas said.Gulls: Content to ride it out, and leave conquering the world to the rodents. Respect.Wild cardsLate entrants! Goumas nominated the honey badger as a long-shot candidate on account of its infamous swagger, which does, indeed, exude “heir apparent” energy. “They’re feisty, tough and appear to be scarily intelligent,” she said. “Perhaps that’s more fantasy than reality though!”And though gulls were more or less ruled out as successors, the researchers I spoke with did consider other birds as successors. Corvids, like crows or ravens, could be formidable candidates due to their exceptional intelligence, which manifests in everything from solving puzzles to holding serious grudges.“Flying also seems like a great way to begin world domination when there are no projectile weapons anymore,” Goumas speculated. “But I wonder if not having hands to manipulate objects with would work against them or at least slow their rise to dominance down enough to give another animal a chance to take that crown.”Brusatte, meanwhile, envisioned a future in which pigeons have stepped into our niche. Instead of using flight to their advantage, though, these beefed-up birds could give up the skies for society life on the ground.“If humans went extinct suddenly, I could imagine some of these urban pests we know so well taking advantage,” he said. “Might some pigeons, in some parts of the world, give up the power of flight in order to get big and move up the food chain? I really do think there is a possibility that there could be six-foot-tall pigeons, waddling on the ground, unable to flap their wings skyward, doing some of the things that humans and other big mammals once did!”The thought experiment itself A false premise? Of course, it’s fun to treat a theoretical evolutionary shakeup like an arc on Succession. That’s why I wrote this story. But the real world is just slightly more complicated. Maybe urban pests would thrive and build their own civilizations from our ashes, or maybe they would collapse in the absence of our voluminous garbage. Maybe multiple clades would rush into our niche and duke it out, or perhaps they might collaborate. Rats and pigeons, working together? Anything is possible in a post-human world.“Without humans, there would be no trash to scavenge!” Goumas said. “And which of the species would dominate? Could they co-dominate? Could they work together? Or would there be another species waiting in the wings? “This is such a difficult question to ponder because, apart from the obvious difficulty in knowing how species would react in the first instance, so much would come down to chance: being in the right place at the right time, or having a particular mutation that puts an individual at an advantage that sets their descendants on a different course.”To that point, Lambert suggested a different angle altogether: “A more interesting question to me is not who is left, or who can survive, but how can we all survive in a somewhat respectful way?”If you liked this blog, please share it! Your referrals help Defector reach new readers, and those new readers always get a few free blogs before encountering our paywall.Becky Ferreira is a science reporter based in Ithaca, N.Y. She writes The Abstract, a weekly science column for 404 Media. Her book First Contact, about the search for alien life, will be out in fall 2025.Sign up for our free newsletterThis is Defector, a new sports blog and media company. We made this place together, we own it together, we run it together. Without access, without favor, without discretion, and without interference.Sign up for our free newsletter© Copyright 2025Made in partnership with Lede

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