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Alternate history often delves into the effects and outcomes of pivotal human choices made at key moments in history. However, unless we exist in an entirely deterministic universe, we can explore the deeper past and imagine alternate Earths shaped by vastly different conditions.
10. What If Pangaea Had Stayed Intact?
Between 300 million and 200 million years ago, Earth's continents were united as a single supercontinent known as Pangaea, which gradually separated to form the continents we recognize today. This separation triggered events such as India colliding with Asia to form the Himalayas. But what if tectonic shifts had never occurred, and Pangaea still dominated one hemisphere, with a vast Tethys Ocean on the other?
It's likely that the world would have less biological diversity since the emergence of new species primarily happens through geographic isolation, which triggers selective pressures and the development of novel genetic traits. Much of the Earth's interior would become arid as moisture-laden clouds wouldn't travel far inland. With excess mass affecting the planet's spin, most of the landmasses would be located in the hot equatorial regions.
Compared to our world, Earth would be about 20 degrees Celsius (36 °F) warmer during the summer. It would also experience massive typhoons, driven by the vast circulation system in the Tethys, which would only be obstructed by island chains or shallow continental shelves.
During the second historical Pangaean period, mammals thrived in the tropical, water-abundant monsoon zones, while reptiles dominated the expansive dry regions, largely due to the fact that mammals consume more water when excreting. Fossil studies of Pangaea show tropical regions dominated by traversodont cynodonts, a now-extinct group of pre-mammals, while temperate areas were largely inhabited by procolophonoids, lizard-like creatures distantly related to modern turtles.
In a modern Pangaea, various regions could have been ruled by entirely different forms of life. Tropical, hot, and wet regions would be filled with a variety of mammals and mammal-like creatures, while the dry interior and temperate zones would have been dominated by reptiles and pseudoreptiles. Although intelligent life might have struggled to emerge due to environmental stasis, if it had, it would have had a catastrophic impact on the opposite climatic region.
9. What If The Earth Had No Tilt?
Seasons on Earth occur due to the planet's tilt as it orbits the Sun, exposing different hemispheres to varying levels of sunlight. Without the Earth's 23-degree tilt, every region would experience about 12 hours of daylight throughout the year, and the Sun would stay perpetually on the horizon at the poles.
The weather would become much more consistent, although slight variations would occur due to the changing distance between the Earth and the Sun during the year. Northern regions would experience constant winter, while the equator would be a humid tropical zone with heavy rainfall. As you moved north or south from the equator, you would pass through regions with unending summer, then temperate spring or autumn, and finally a cold, inhospitable winter closer to the poles.
Many believe the Earth’s tilt was caused by a massive collision, which also led to the formation of the Moon. According to the Rare Earth Hypothesis, this tilt played a crucial role in fostering life. A planet with no tilt might not be able to retain an atmosphere, as gases would evaporate into space from the equator's intense sunlight and freeze at the poles, falling back to the surface.
If life managed to survive in such a scenario, it would still be disastrous for any intelligent species like us. Without seasons and with constant rainfall in the tropics, traditional agriculture would be impossible. Diseases would likely thrive around the equator. If an intelligent species like ours did evolve, they would have little incentive to trigger an industrial revolution, as the need for technologies to heat homes during cold winters would be nonexistent.
8. What If Earth Had A Different Tilt or Rotation?
Changing the Earth's tilt would have profound impacts on the climate and environment, with the angle affecting how much sunlight reaches the planet and altering seasonal intensity. If the Earth were tilted by 90 degrees, the seasons would be incredibly extreme. As the Earth orbits the Sun, the poles would alternatively point directly at the Sun and remain perpendicular to it. One hemisphere would be constantly heated by the Sun, while the other would remain in perpetual cold darkness. A few months later, both poles would experience a low Sun angle, and the equator would have equal amounts of day and night, with the Sun rising in the north and setting in the south.
Life on such a planet might be unlikely due to the intense yearly cycles of radiation sterilization during the summer and extreme freezing temperatures during winter. However, some extremophiles on Earth, organisms that thrive in harsh conditions, could potentially endure these changes. If these extremophiles evolved into more complex life forms, they would likely develop significant adaptations such as hibernation or migration to survive.
Chris Wayan, an artist and passionate dreamer, has delved into a variety of hypothetical scenarios by changing the Earth's rotation axis. He preserved the Earth's 2-degree tilt but shifted the locations of the poles on the planet’s surface. In one concept called 'Seapole,' Wayan tilted the Earth so both poles were above water, then predicted the resulting climate effects. By removing the ice sheets of Antarctica and Greenland, he envisioned a world that was warmer and wetter, with potentially increased biomass and biodiversity.
A reversed scenario called “Shiveria” places ice caps over the land at both ends (China and northern South America), creating a generally colder and drier world. However, Antarctica would become tropical, and the Mediterranean would turn into a hothouse, which Wayan refers to as “the Abyss.”
Turning the Earth upside down completely reverses water currents, winds, and rainfall patterns, resulting in a world where China and North America are deserts, but the overall environment may actually be more favorable for life. XKCD also explored a similar concept, rotating the Earth to place the poles at the equator. This scenario resembles Shiveria, and the site discusses how it would impact cities worldwide, turning Manila into something akin to Reykjavik, Moscow into a dry desert, and London into a sweltering metropolis.
7. What If South America Were an Island Continent?
From the late Jurassic period until about million years ago, North and South America were separated by water. Both continents evolved independently for nearly 160 million years, with some limited biotic exchange occurring through emerging Caribbean islands around 80 million years ago and the Central American peninsula around 20 million years ago.
During that era, South America, much like Australia, was dominated by marsupials, along with a variety of unusual placental, hooved animals (including the first camels) and the edentate (“lacking teeth”) ancestors of anteaters, armadillos, and sloths. In contrast, North America, Eurasia, and Africa were populated by placental mammals, with no surviving marsupial species.
All existing marsupials trace their origins back to South America, with kangaroos and opossums sharing common genetic ancestors. The South American marsupial fauna likely included various carnivorous species—pouched predators known as 'borhyaenoids'—which resembled weasels, dogs, bears, and even saber-toothed tigers. However, it remains uncertain whether these creatures actually carried their offspring in pouches.
When the two American continents merged, mammals from North America spread into South America, outcompeting most marsupials. At the same time, reptiles, birds, and a few mammals from South America migrated north.
Had the two continents remained separated, it's likely that many marsupials would have persisted into modern times, creating an environment as strange and unique as Australia. Unfortunately, if humans or a close equivalent had arrived, they would likely have brought placental mammals from Eurasia, potentially triggering an extinction crisis similar to the one faced by Australia's marsupials in our world.
6. What If the Mediterranean Had Stayed Closed?
Around six million years ago, the Strait of Gibraltar closed, leaving the Mediterranean Sea only connected to the Atlantic through two narrow channels. The results were catastrophic. As tectonic forces pushed Africa toward Europe, the water exit point was sealed, but salty water continued to flow in from another direction. Without an outlet, the Mediterranean began to evaporate, creating an immense salty brine, resembling a vast Dead Sea, with a 1.6-kilometer-high (1 mi) layer of salt forming on the seafloor. Most marine life in the Mediterranean became extinct during this event, known as the 'Messinian salinity crisis.'
After hundreds of thousands of years, the Mediterranean was once again connected to the Atlantic during the 'Zanclean flood.' The sea quickly refilled, causing land bridges to submerge between Europe and North Africa. Animal species were isolated on islands, where they evolved into new species. Meanwhile, marine life from the Atlantic adapted rapidly to recolonize the Mediterranean.
What if this event had never occurred, and the Mediterranean remained a dry, salty pan? In that case, it's likely that humans would have arrived in Europe much earlier than they did in our world, migrating through the salty lowlands rather than taking a longer route through the Middle East.
Salt is an incredibly valuable resource. As human civilization progressed, it’s probable that cultures in the Mediterranean would have exploited this resource, trading it with distant regions of Africa and Asia. Given the necessity of salt for human survival in a diet rich in cereals, its abundant availability could have accelerated the development of agriculture in the Western hemisphere.
Given this scenario, salt might have been considered less valuable due to its abundance, possibly losing its religious or symbolic importance and becoming just a cheap commodity. The phrase 'worth their salt' could have even turned into an insult rather than a compliment.
5. What If There Were No Large Metal Deposits on Earth?
Humans and animals rely on metals for survival. But what if metals like copper had never formed concentrated, exploitable deposits, or if they were located in regions that early humans couldn’t access, such as under ice caps or deep beneath the ocean? While the evolution of more efficient, advanced Stone Age technologies would have continued, it’s likely that entire paths of development would have been closed off to humanity (or any intelligent life in such a world).
Even without metals, the transition from the Neolithic period would still have happened, as the agricultural revolution would lead to the rise of settlements and larger populations. The plow and the wheel would still have revolutionized life for this Stone Age society, but the absence of useful metals might have hindered the development of mining, trade, and social structures. The existence of sophisticated civilizations in the Americas without metals suggests that a similar development might have occurred in Eurasia. However, if the lack of metal deposits also included gold and silver, the economies and arts of such cultures might have appeared rather dull.
In Mesoamerica, the scarcity of metals led to the advanced use of volcanic glass obsidian, a material so sharp it could rival a modern scalpel, though it was also fragile. The Aztecs crafted weapons like swords with multiple glass blades, along with arrowheads, spears, and knives from obsidian. Beyond its practicality, obsidian held significant religious meaning, contributing to the Aztec culture’s strong affinity for self-sacrifice. With such sharp tools, performing ritual bloodletting by cutting one’s tongue or ear would have been less painful than we might imagine.
Obsidian, sourced from places like Ethiopia and the Near East, was also utilized in ancient Egypt. However, its use in crafting knives and sickles gradually faded as metallurgy took hold, although it continued to be valued as a medium for artistic expression. If metals hadn’t been available, Egyptian civilization might have needed to control obsidian more aggressively, expanding into the Near East and East Africa to secure key sources. In Europe, one of the richest obsidian deposits was around the Carpathian Mountains, where another culture of glass-edged sword wielders could have emerged.
It remains uncertain how advanced a society relying solely on glass, stone, and ceramics might have become. Many innovations in transportation, cooking, and engineering would likely have been beyond reach. The industrial revolution as we know it would not have occurred. While such cultures could have made great strides in fields like medicine and astronomy, it’s unlikely they would ever have reached the Moon.
4. What If The Sahara Was Still Wet?
Up until around 5,000 years ago, the Sahara was a vibrant landscape filled with lakes and grasslands, home to animals like hippos and giraffes. This was during the African humid period, a time whose precise origins and conclusion remain a mystery to scientists. The climate during this period enabled early humans to migrate out of Africa, otherwise the Sahara could have posed a significant obstacle. The shift to the present desert climate likely occurred about 3,000 years ago, prompting the inhabitants to move to more hospitable areas.
But imagine if the humid period had never come to an end. During this time, several large lakes existed in southern Libya, and Lake Chad was significantly larger than it is now. Around these lakes, ancient civilizations created art and tools, leaving behind bones and artifacts that are now buried beneath the harsh sands. In 2000, paleontologists searching for dinosaur fossils in southern Niger uncovered the remains of numerous humans, along with clay pots, beads, stone tools, and the bones of crocodiles, fish, clams, turtles, and hippos.
A follow-up expedition in 2003 unearthed at least 173 burial sites. Based on the design of pottery fragments, these tribes were identified as the extinct Kiffian and Tenerian tribes. Fossil records also reveal that the desert areas of Sudan once supported large herds of cattle.
Historically, the Sahara acted as a barrier that kept sub-Saharan African cultures isolated from those in North Africa and the Mediterranean. Because technological advances from the Fertile Crescent couldn’t easily cross the Sahara, many innovations from Eurasia either didn’t reach sub-Saharan Africa or had to be developed independently.
On the flip side, a lush Sahara would have encouraged the early development of settled towns, cities, and centralized governments in the region. Not only would this have expanded the areas occupied by civilized societies and the reach of ancient trade networks, but it would also have fostered greater genetic, linguistic, and cultural exchanges between Africa and Eurasia.
Tropical diseases could have posed a challenge in certain regions. Additionally, it's likely that the cultures of a wetter Sahara would have experienced varying levels of development, much like other parts of the world. However, in general, the level of human civilization in the region would likely have been higher, potentially leading to accelerated progress. The Sahara could have supported a vast, unified culture similar to China, which would have had a significant influence on the development of Mediterranean and European civilizations.
3. What If There Had Been Slightly Less Ice During The Ice Ages?
In 2006, Steven Dutch of the University of Wisconsin presented a paper to the Geological Society of America discussing the effects of slightly less ice during the Ice Ages. He explored what might have happened if the North American ice sheets had never reached as far south as they did, and if the Scottish and Scandinavian ice sheets had never merged. This would have had three major consequences: the Missouri River would have followed its original path into Hudson Bay, the Great Lakes and the Ohio River would never have formed, and the English Channel would not exist.
In our world, the formation of the Scandinavian and Scottish ice caps created a massive proglacial lake that eventually overflowed into the ancestral Rhine-Thames river system, resulting in the creation of the English Channel. Had the two ice caps never merged, the water would have flowed north, leaving a land bridge between England and mainland Europe. This would have removed the natural defensive advantage Britain had over mainland Europe, leading to significant shifts in migration, settlement, and cultural exchange in the West.
In North America, the absence of ice caps would have drastically altered the drainage systems. The pre-Pleistocene Teays River would still be intact, and the Niagara River would have kept its ancient course. As a result, Niagara Falls would not exist. The St. Lawrence River would have become the most accessible route across the Appalachians, potentially altering the patterns of colonization. Additionally, the changes in the Missouri River would have disrupted the east-to-west waterways that were pivotal during the Lewis and Clark expedition in our reality.
Had this occurred, the expansion of European settlers across North America would have been much slower due to fewer navigable waterways. This migration might have taken place from the North, possibly involving a group that was a blend of English and French cultures, or even a people whose culture was entirely unfamiliar to us.
2. What If Doggerland Still Existed?
Around 8,200 years ago, a low-lying landmass in the North Sea, known as 'Doggerland' or 'Britain’s Atlantis,' existed. This land was a remnant of a once vast region that spanned the entire North Sea area, featuring hills, marshes, wooded valleys, and swamps. It was inhabited by Mesolithic people who migrated seasonally, hunting and gathering berries for sustenance. Artifacts and animal remains from this time are sometimes found by North Sea fishermen. Eventually, climate change caused the area to flood, prompting the people to relocate.
The last part of greater Doggerland was located near Dogger Bank, just beneath the North Sea. Recent studies suggest that this final remnant and its inhabitants were destroyed about 8,200 years ago by a 5-meter tsunami, resulting from the collapse of 3,000 cubic kilometers of sediment in an event called the 'Storegga slide.'
But imagine if the Storegga slide had never happened or if Dogger Bank had been slightly higher.
If the humans in this area had survived, they could have played a significant role in the development of civilization, even if it were delayed due to their isolation. The original Mesolithic population would likely have been replaced by Neolithic settlers from the mainland, who may have eventually been overtaken by Celtic invaders, similar to the historical patterns in the British Isles.
The Celts were likely displaced by the expansion of Germanic invaders, particularly since the Celts probably had a lower population density in Doggerland compared to the British Isles and mainland Europe. It is possible that the North Germanic Doggerlanders helped maintain a cultural connection between Norse traditions and those of Britain. There’s also a chance that Doggerland was settled by the Balts, either a group that no longer exists or one that never existed in our world.
A surviving Doggerland would still be highly vulnerable to climate change. Global warming would pose similar existential risks as those faced by low-lying Pacific islands. However, a wealthy, developed Northern European country threatened with extinction might have more influence in shaping environmental policies across Europe.
1. What If the Gulf Stream Ceased to Exist?
The Gulf Stream is a crucial ocean current in the northern hemisphere, running from Florida to northwestern Europe. It carries warm Caribbean waters across the Atlantic, warming Europe. Without the Gulf Stream, northern Europe would be as cold as Canada at the same latitude. The system relies on temperature and salinity differences in seawater: denser, colder, and saltier water from the North Atlantic flows south, warms up, becomes less dense, and then flows back north.
The system has experienced multiple shutdowns due to an influx of freshwater and changes in the amount of solar energy reaching the Earth. The Gulf Stream made its return 11,700 years ago, marking the end of the last ice age. Without increased solar energy, this might not have happened, and northwestern Europe could have remained trapped in ice age conditions for a longer time, with a more expansive Arctic ice sheet and larger Alpine glaciers.
In this scenario, the region would have been inhospitable for farming and the rise of civilization. The people of northwestern Europe might have resembled the Saami or the Inuit rather than the historical cultures we know. Western civilizations would have been confined to the Mediterranean, North Africa, and the Middle East. On the brighter side, it would likely have been too cold for aggressive Central Asian tribes, like the Huns or Mongols, to invade and conquer.
An intriguing possibility arises if the Gulf Stream reappeared after settled civilizations had already developed. As the ice melted, a new frontier would emerge, offering fresh opportunities for settlement and conquest to the overcrowded cities along the southern Mediterranean coast.
