Every species that has ever walked, crawled, or flown across our planet faces an inevitable end. Dinosaurs learned that lesson 66 million years ago when an asteroid slammed into what we now call Mexico. Scientists have long debated what will ultimately wipe out humanity, and our fellow mammals, but new research suggests our demise won’t come from space rocks or nuclear war. Instead, three separate catastrophic events will converge at once, creating conditions so extreme that warm-blooded life simply cannot exist.
University of Bristol researchers used supercomputer climate models to peer 250 million years into Earth’s future, and what they found paints a grim picture. For all our technological advances and evolutionary resilience, mammals appear headed toward complete extinction during a period when our planet transforms into something unrecognizable. While that timeline might seem comforting, the study carries an urgent warning about the climate crisis we face right now.
Continental Collision Creates Perfect Storm for Mass Die-Off
Tectonic plates beneath our feet move at roughly the same speed fingernails grow, but over millions of years, those tiny movements add up to dramatic changes. All seven continents we know today will eventually crash into each other, forming one massive landmass scientists call Pangea Ultima. Plate tectonics last created a supercontinent about 200 million years ago, and geological evidence shows Earth follows a predictable cycle of continental assembly and breakup every 400 to 600 million years.
When landmasses merge into Pangea Ultima, three separate extinction mechanisms will trigger simultaneously. Lead author Dr. Alexander Farnsworth explained that “the newly-emerged supercontinent would effectively create a triple whammy, comprising the continentality effect, hotter sun and more CO2 in the atmosphere, of increasing heat for much of the planet.” Each threat alone would challenge mammalian survival, but together they create an environment where life as we know it becomes impossible.
Volcanic eruptions will become far more frequent as continents collide and tectonic stress builds along fault lines. Each eruption pumps massive quantities of carbon dioxide into the atmosphere, warming the planet through an enhanced greenhouse effect. Meanwhile, our sun continues its natural lifecycle, growing brighter and emitting approximately 2.5 percent more energy than it does today. Solar luminosity increases by roughly 1 percent every 110 million years, and while that sounds modest, the extra heat compounds the warming from volcanic CO2 emissions. Add in the continentality effect, where interior regions of large landmasses experience extreme temperatures because they sit far from moderating ocean influences, and you have a recipe for planetary catastrophe.
Scorching Temperatures Push Past Biological Breaking Points
Mammals have survived ice ages, asteroid impacts, and dramatic climate swings throughout our 55-million-year reign as Earth’s dominant terrestrial animals. We evolved remarkable adaptations like fur for cold protection, hibernation for surviving harsh winters, and even short periods of warm-weather dormancy called aestivation. But all those survival strategies have limits, and Earth’s future climate will blow past every biological safeguard mammals possess.
Climate models predict surface temperatures between 40 and 70 degrees Celsius across most of Pangea Ultima, with widespread areas consistently hitting 40 to 50 degrees. Daily temperature extremes will spike even higher, and crushing humidity levels will make those temperatures lethal. Mammals regulate body temperature through evaporative cooling, sweating or panting to shed excess heat, but that mechanism fails when wet-bulb temperatures exceed 35 degrees Celsius. At that threshold, air becomes so saturated with moisture that sweat cannot evaporate from skin, making it physically impossible for mammals to cool down regardless of how much water they drink.
Dr. Farnsworth and his team explained that “widespread temperatures of between 40 to 50 degrees Celsius, and even greater daily extremes, compounded by high levels of humidity would ultimately seal our fate. Humans, along with many other species, would expire due to their inability to shed this heat through sweat, cooling their bodies.” Hyperthermia sets in after just six hours of exposure to these conditions, and death follows soon after. Research shows that mammalian upper temperature tolerance has remained constant across millions of years of evolution, hovering around 40 degrees Celsius regardless of species or geographic location. While mammals have successfully adapted to survive colder environments by evolving thicker fur and enhanced cold tolerance, our ability to handle heat has barely budged.
Habitable Land Shrinks to Tiny Fraction of Surface
Between extreme heat, continental deserts, and regions too cold to support plant growth, only 8 to 16 percent of land on Pangea Ultima will remain habitable for mammals. Compare that to the 66 percent of land currently suitable for mammalian life, and the scale of this extinction becomes clear. Most tropical and mid-latitude zones will become death traps where temperatures routinely exceed what warm-blooded creatures can withstand.
High-latitude regions near the poles might offer limited refuge from searing heat, but even those areas present problems. Seasonal temperature swings will still dip below freezing during winter months, cutting off freshwater supplies and forcing plants into dormancy. Migration between habitable zones becomes nearly impossible because continent-wide deserts and arid wastelands separate the few remaining pockets where mammals could survive. Animals attempting to cross these barriers would need to traverse thousands of kilometers through 50-degree heat with almost no available water or food.
Vapor pressure deficit, a measure of how much moisture air can still absorb, will reach levels three to four times higher than the modern Gobi Desert throughout regions between 50 degrees north and 50 degrees south latitude. Plants need water to survive, but under such extreme dryness, they shut down photosynthesis to avoid fatal moisture loss. When plants die, herbivores starve, and carnivores soon follow. Even species that might theoretically tolerate the heat would find themselves in a barren landscape devoid of the food and water necessary to sustain life.
Atmospheric Carbon Dioxide Doubles from Volcanic Outgassing
Supercomputer models combined with biogeochemical calculations predict that atmospheric CO2 levels will climb to somewhere between 410 and 816 parts per million during the Pangea Ultima era. Current atmospheric CO2 sits around 400 ppm, so these projections represent a near doubling of greenhouse gas concentrations. Scientists calculated future CO2 by modeling tectonic plate movement, ocean chemistry, and biological carbon cycling to map inputs and outputs of the gas over geological timescales.
Frequent volcanic eruptions along the boundaries where continents collide will pump huge volumes of CO2 into the air. Historical records from previous supercontinent formations show atmospheric CO2 often spiked to between 1,000 and 3,000 ppm during periods of intense volcanic activity. Weathering processes that normally draw down atmospheric carbon through chemical reactions with rocks become less effective when continents merge, because massive interior deserts lack the rainfall needed to drive those reactions. Moisture from oceans cannot penetrate deep into continental interiors, reducing runoff and slowing the natural carbon cycle that helps regulate Earth’s temperature.
Burning every available fossil fuel on Earth today would increase global temperatures by roughly 12 degrees Celsius, but the combined effects of supercontinent formation, increased solar output, and elevated CO2 will push temperatures far beyond that level. Natural geological processes alone will create warming that exceeds anything humans could accomplish, even if we tried to deliberately heat the planet.
Evolutionary Adaptation Cannot Save Mammals from Heat Death
About half of all modern mammal species hibernate to survive periods of cold and food scarcity, but hibernation offers little protection against extreme heat. Aestivation, the warm-weather equivalent of hibernation, works for only a handful of species and typically lasts just days or weeks rather than months. Mammals attempting to aestivate through the hottest periods on Pangea Ultima would need to remain dormant for three months or more, and even then, the shoulder months before and after peak summer would still exceed survivable temperature thresholds.
Evolution moves slowly when it comes to heat tolerance. Mammals have increased their upper temperature limits by only 0.6 degrees Celsius per million years, far too slow to adapt to the rapid warming Pangea Ultima will bring. Meanwhile, plant photosynthesis begins failing at temperatures above 40 to 60 degrees Celsius because heat damages the molecular machinery that converts sunlight into chemical energy. When plants die, the entire terrestrial food web collapses, removing any possibility that mammals could evolve their way out of extinction.
Some small burrowing mammals might find temporary refuge underground where temperatures stay cooler, but even caves and burrows cannot protect animals that need to eat and drink. Food and water scarcity will kill species that might otherwise tolerate the heat, and juvenile mammals with less developed thermoregulatory systems will die even faster than adults.
Current Climate Crisis Demands Action Despite Distant Timeline
While Earth faces this apocalyptic scenario 250 million years from now, researchers stress that humanity cannot afford complacency. Dr. Eunice Lo, Research Fellow in Climate Change and Health at the University of Bristol, emphasized that “it is vitally important not to lose sight of our current climate crisis, which is a result of human emissions of greenhouse gases. While we are predicting an uninhabitable planet in 250 million years, today we are already experiencing extreme heat that is detrimental to human health.” Reaching net-zero emissions remains urgent because human activity is already pushing some regions toward dangerous temperature thresholds.
Present-day climate change operates on human timescales measured in decades rather than millions of years, and communities around the world already face deadly heat waves, droughts, and ecosystem collapse. Research into Earth’s distant future helps us understand the boundaries of mammalian survival and reminds us that our planet’s habitability is not guaranteed. Small changes in atmospheric composition, solar output, and continental configuration can push Earth past tipping points where life becomes untenable.
Understanding these distant threats helps scientists develop better criteria for identifying planets that could support complex life. Every piece of knowledge about Earth’s past and future climates improves our ability to spot promising exoplanets and interpret the data we collect from them. As humanity looks toward the stars for potential homes or signs of extraterrestrial life, we must remember that habitability depends on far more than just distance from a star.
