If MLP isn't gonna make its own lore I'm just gonna make my own.
This is my personal headcanon for the history of ponies and other creatures! Note that most of the canon backstory for Hearth's Warming and the war between earth ponies, unicorns, and pegasi has been disregarded. This is pretty far into AU territory, and is mainly only canon to the Duxverse. I'm probably going to make a separate piece of my versions of the mane six.
A long time ago, before ponies even existed, there was no Equestria. Instead, there was Zacherle, a planet that was inhabited by thousands of ancient creatures, many of which are now extinct. Among these creatures were the predecessors to the ponies we know today— feleogriffs, draicarns, and yaks.
The draicarns were large (their average height was seven feet), bulky, egg-laying mammals with curved horns along their backs and reptilian-looking tails. Their hooves were split into three sections, and on each was a large, flat claw, used to dig up the burrows of the small animals they ate. They weren't stealthy, but they had incredible physical strength, and the ability to conjure fire from their throats, eyes, and nostrils. They lived in the valleys of Zacherle until a large earthquake split their land and drove them out of the area. Three groups formed from them— one went to the forests, one to the mountains, and one to the marshes. The group of draicarns in the forests didn't have much use for the horns on their backs. Over time, they disappeared completely, leaving only a trail of plated scales in their place. The horn on their foreheads stayed, however, and grew less sharp as it began to split into branches to help with camouflage. They began growing hair on the end of their now-thinner tail, and a mane around their neck and head that scared off larger predators. Their hooves got smaller, they lost their toes, and their overall size diminished until they were only about five and a half feet tall on average. They still had their fire-making abilities and laid eggs, but they were noticeably less reptilian. They became the mysterious kirin. In the mountains, the draicarns quickly began to grow. The abundance of edible minerals there meant they had more than enough food to go around, and their offspring grew even more with each new generation. The reason for their wings is a bit of a mystery, but they may have developed due to breeding with nearby draconequi. Their claws got sharper and more defined, their tails got longer, and their teeth got sharper. They harnessed their pyromancy to become the most fearsome fire-breathers known to Zacherle: dragons. In the marshes, the draicarns got much smoother. Like kirin, they lost all horns except the ones on their heads, and traded their toes for hooves. They grew manes, hair on their tails, and magical abilities. They started being able to do much more than breathe fire (most of them even lost that ability). They were called traditional unicorns, and they later gave rise to the unicorn ponies of Equestria.
The feleogriffs were small, agile birds with clawed paws. They were covered in feathers, and had pointed noses and long, prehensile tails. Feleogriffs inhabited the jungles and skies of eastern Zacherle, feeding off of insects and small mammals. Though they were tiny, they more than made up for it in speed and strategy. They were determined hunters that never backed down from a challenge. This was what eventually caused their downfall. Feleogriffs often got territorial, which caused problems within the species. Fighting between colonies made it hard to produce more feleogriffs without inbreeding, and their numbers began to diminish slowly. Sensing that they were in danger, the feleogriffs split off into three groups— one to the arid mountains, one to the beaches, and one to the plains. The feleogriffs in the mountains faced challenges. It was difficult to hunt the larger prey there with only small retractable claws, and it was even harder to eat the meat of that prey with a snout. Over time, this group grew, changed, and evolved, gaining claws, beaks, and larger wings. They called themselves griffons, and named their new home Griffonstone. On the beaches, a similar situation arose. Catching fish with paws was not an easy task. To survive, the feleogriffs there also delevoped claws on their front legs, while their back legs became hooves to better allow for walking on sand. The feathers along their crests got more colorful and vibrant to help ward off predators, and they lost their tails, which were replaced by even more feathers. The hippogriffs named their home Mount Eris. The last group of feleogriffs, who migrated to the plains, changed the most drastically. Since they could only eat the berries and nuts that grew on the bushes and trees in the plains, they had to travel almost constantly to find food. This was tough for creatures with paws, so they traded them for hooves. Their tails were replaced with hair, and they developed manes to help keep the bright sun off their skin. They became the ancestors of today's pegasus ponies— pygmy pegasi.
The yaks are some of the only species of the ancient world that still exist. They are large mammals that are covered in a thick layer of fur to combat the cold arctic environments in which they live, and they have a set of horns protruding from the sides of their head that they use to break sheets of ice. Their hooves are wide and flat to allow them to walk on top of layers of snow. They are incredibly hearty creatures; an adult yak can go without food for months. They feed mainly on grasses and other small plants that grow around their habitat, and have a kind of yearly route that they follow around several mountain ranges so that their food supply has time to regrow. The yaks, like many other species, split into groups at one point or another. One group moved just outside of the arctic mountains to the surrounding tundra, one group went further south to the deserts, and one group ended up on an island near the rocky plains in the west. In the tundra, the yaks kept their shaggy fur, but it became thinner and shorter. They developed long manes to keep snow off their fur, and tougher hooves to deal with rockier ground. Their horns, no longer necessary for making cave burrows, soon faded. Their overall body shape changed over time as well to be less hunched and a bit taller. These creatures became known as Clydesdale horses, and would eventually lead to earth ponies. The third group, in the deserts, lost almost all of their fur, and were soon only covered by a thin layer of hair. Their hooves widened so they could walk on sand, their legs got longer to keep them further away from the hot ground, and their horns disappeared. They now live in modern Saddle Arabia, and are known as Saddle Arabian horses. The smallest of the yak descendants barely reached three feet at the end of their evolution. They also lost their horns and fur, and grew manes, though their hair stayed short. They themselves got shorter since being low to the ground helped them keep balance when climbing over the rocky terrain on which they lived. They were called Shetland horses.
Over time, a few species began to migrate to the same area— a large valley covered in nutrient grasses, enormous trees that provided fruit and shade, and large, clear lakes. The traditional unicorns were the first to discover this haven, and quickly claimed it as their own. The pygmy pegasi followed soon after, and tried to kick the traditional unicorns out. A feud between them broke out, and they fought over the territory for years. When the Clydesdale horses arrived, things only got worse. One large problem was that the groups could not understand each other, and could not communicate with each other at all. It wasn't long before an all-out war broke out between the species. They attacked each other's camps, killed each other's leaders, stole each other's food— anything they could do to try and drive them out of the valley. Soon, a sudden and violent winter arrived, and the land began to freeze over. This only made the species more violent towards each other. As temperatures dropped rapidly, the creatures were driven west, towards the less inhabited parts of the valley. Seeking shelter, a few of them ran into a nearby cave, and were horrified when the entrance froze shut behind them. In the darkness, a light appeared, cast by one of the creatures in the cave— a traditional unicorn, standing next to a Clydesdale horse and a pygmy pegasus. Faced with their apparent doom, the three of them didn't fight. Honestly, none of them had ever really seen a good reason for their species to hate each other. They just stood together, watching the ice slowly creep across the walls and floor of the cave. When it had almost completely surrounded them, the unicorn— whose name was Lumera— extended her hoof to the pygmy pegasus. After a moment, the small stallion, Vallar, took her hoof, and offered his own to the Clydesdale horse, Payakos. She completed the circle, holding the hoof of both creatures. It was in this moment that the Fire of Friendship was born, and the force of it drove away the winter in the valley. When the three creatures in the cave saw what had happened, Lumera turned to her companions and spoke— and they were shocked to find that they could understand her. The creatures outside, who they had believed were dead, also began to speak to each other, and rejoiced in the banishing of the freeze. They also noticed another change— they now each had a mark on their flanks. No one could figure out why, but these marks seemed to match up with the talents of the creatures they were on. Because of this, they were dubbed "destiny marks." The three species agreed to put aside their differences and share the valley. They named their new home Equestria.
Now that they had a common language, the species began to form bonds with each other. Of course, this led to many hybrid children, who were called ponies. Ponies with horns were unicorn ponies, ponies with wings were pegasus ponies, and ponies with neither were earth ponies. Over time, the hybrids began to be more consistent in their appearances, eventually leading to the ponies we know today.
There were a few family lines that only bred within their species. Rarity's mother, for example, is a full-blooded traditional unicorn. She hated the way her family treated ponies, so she changed her name from Jasmine Belle to Cookie Crumbles and moved to Ponyville, where she met Hondo Flanks. Her family does not acknowledge her marriage or her pony children. Rainbow Dash's mother, while a pegasus pony, inherited the gene that makes pygmy pegasi small, and passed it to her daughter. Pinkie Pie is from a family of Clydesdales.
Fun facts!
-Feleogriffs, draicarns, and yaks could all communicate in their own languages, and had quite civilized societies. The feleogriffs were organized in tribes, the draicarns were a pseudo-monarchy, and the yaks were in villages that traded with each other. -The original language of the feleogriffs was Latin, the original language of the yaks was Russian, and the original language of the draicarns was Chinese. There are quite a few ponies who can still speak the language of their ancestors. Pinkie Pie is fluent in Russian, which their uncle taught them, Fluttershy learned a bit of Latin through osmosis, and Rarity grew up in a bilingual household— her mother taught her Chinese and her father taught her Caballish (the language of Equestrian ponies). -The story of the Pillars of Equestria takes place only a few years after the unification of the species. -Mistmane was a traditional unicorn, but Starswirl the bearded was a unicorn pony (his mother was a Clydesdale horse). -Flash Magnus was a pygmy pegasus, and Somnambula was a pegasus pony. -Rockhoof was a clydesdale horse, and Mage Meadowbrook was an earth pony. -Pegasi with the pygmy gene are often affectionately referred to as pixies. -In rare cases, ponies can be born with parts of draicarns, feleogriffs, or yaks (multiple horns, prehensile and hairless tails, cloven hooves, etc.) -Earth ponies of all genders grow beards very quickly. Pinkie Pie is particularly proud of theirs. -Earth ponies are generally the tallest of the three pony types, followed by unicorn ponies, then pegasus ponies. -Some unicorn ponies who have a lot of traditional unicorn blood can breathe a small amount of fire or smoke. When she's really miffed, Rarity can cough up some embers. -Lumera, Vallar, and Payakos had matching destiny marks (which later came to be known as cutie marks). Alicorns were brought into existence when Celestia, a young unicorn, had enough magic to raise the sun on her own. She was given a blessing from Zacherle itself- the magic of not only unicorns, but pegasi and earth ponies as well. She also gained the ability to give this blessing to others. When Luna raised the moon on a night when Celestia was sick, Celestia gave her sister alicornhood and control over the moon, the stars, and the night sky.
Aaaaaand that's how Equestria was made! Hachi machi this is a big file and it took WAY too long.