Tens of thousands of years ago, merfolk were a nomadic race, hunting mainly whale in the depths of the ocean with their dolphin companions. About 40,000 years ago, there was the first recorded evidence of merpopulations above 500. Around that time, kelp cultivation became a popular strategy for food generation, as the kelp could be both eaten and used as a way to attract smaller fish species.
Throughout the next thousand years, mermaids became common hunters, as their songs were able to attract a wide variety of different sea creatures. Mermen would stay home and tend to their crops and children. It was around this time that merfolk began to see a need for record-keeping and they developed a method of weaving seaweed stems and sea shells together to keep track of a number of different things: acres of land, number of children, fish killed in one day, etc.
Though it was a simpler time, ancient merfolk also began devising the basis for all modern language and discussion. Tones in song were to express mood, while hand-signals were used to express more complex ideas. Eventually, it was found that sea salt could crystallize to form a hardened stone to use for writing, and circular glyphs were created to replace the old counting system of yore.
As technology grew more and more advanced, merpopulations became more expansive, starting in the great trench and extending to every sea in the world. At the same time, they began to diversify more. As mermaids began hunting fish closer to the ocean's surface, they would often faint due to the pressure differential. To counteract this, they developed fatty deposits on their chest that would expand and contract as they swam closer to the surface. Mermen, having to quickly and continuously inscribe salt into stone, developed much smaller, but precise arms.
Eventually, mermen began to develop rigorous mathematical and scientific ideas, such as the art of camouflage and luminescence, which were both used to help aid mermaid hunting expeditions. Around 200 years ago, electricity was discovered. It was powerful and destructive, but incredibly useful, as it could be channeled across wires smelted near the lava-pits. Since this discovery, the world has changed drastically, and we began to see the world around us today.
First came electronic music, which was used both for hunting and for entertainment. Then came intricate devices to mimic merfolk hand-gestures, which could transmit discussion across long distances. This eventually became wireless and portable, creating a small box all merfolk would carry around to call others when necessary. Soon thereafter, screens were developed that would allow for the projection of signals beyond just sign language and sound.
At the same time, mermaids developed body-strengthening techniques that would allow them to breach the surface of the water for short periods of time. They would come back telling stories of a strangely merfolk-like race of creatures that would ride on the backs of synthetic sea creatures. Most people thought this was crazy. How could anything survive on the surface without any pressure to keep their bodies in-tact? Absolutely insane!
Well, that was what most merfolks thought... Until about 70 years ago. There, somewhere in the north sea, one of the giant creatures swam to the bottom of the ocean. It was huge -- much larger than anything the merfolk had ever created before and composed of a bunch of intricate rooms and hallways.
Worse, inside of some rooms, were the bodies of the unknown creatures mermaids would tell stories of. They were half merfolk, but had additional arms where their fins should have been. None of them were completely in-tact, but that didn't matter. It was then that merfolk learned they were not the only intelligent creatures on Earth.
It was a scary moment for merfolk everywhere. Their scientists analyzed the creatures as best as they could and developed new methods for creating large sheets of metal, which were used to make satellites that would watch the land creatures from afar.
It was not clear if the new race was more or less advanced than the merfolk, but they were way more savage. The merfolk watched as the landfolk fought among themselves time and time again.
No matter the case, the landfolk would occasionally drop their technology into the depths of the ocean, and the merfolk would learn what they could about landfolk civilization. Occasionally, the technology would be revolutionary. Other times, merfolk would scratch their heads, trying to figure out what the devices could be use for.
No matter the case, today was a monumental day. After half a century since the Great Land Initiative, merfolk were finally able to create a satellite capable of carrying a merman and mermaid onto the surface. Merfolk everywhere were tuned in and watching the historic launch and counting down in the comfort of their own home.
10, 9, 8, 7, 6, 5, 4, 3, 2, 1... Lift off.
In a myriad of bubbles, the overmarine was off. No one quite knew what they would find.
Would the landfolk be hostile? Would the merfolk survive the expedition? What technology might be found on land that merfolk had never thought of before?
One thing was certain: after today, merfolk would never be alone again.
NOTE: I really like the world in this one, but the writing could have been better...