Humans are a race of bipedal humanoids in the Chrono series. According to the pictographs at Fort Dragonia, humans evolved (or "transformed") when Lavos fell from the sky, collided with dreamstone, and created the Frozen Flame. This unstable mineral sparked the evolutionary process in humans, causing them to gain intelligence. The transcript claims that, like Lavos, humans began to devour the planet.
The Reptites, walking on land after years of sea-dwelling, fought with the humans over control of the lands. In an alternate timeline, the Dragonians, an offshoot of Reptites, won the war against the humans and built a civilization. In the altered timeline, a crew of anachronistic warriors (Crono and his friends in Chrono Trigger) assured a human victory by assisting Ayla and the other Iokans with defeating Azala, queen of the Reptites.
A great Ice Age befell the planet after Azala's defeat. At this time, humankind discovered it had an affinity for magic, thus building lavish cities and palaces that floated above the main land. Here, various technological advancements were made, including the ability to travel by air, as represented by the Blackbird or on beams of sunlight, as represented by the Skyways. Sometimes before this, the ability to write and print texts developed. Before the invention of the Mammon Machine, Sun Stone was used as the primary power source for these cities.
Eventually, the zeal of the human kingdom caused it to grow greedy for magical power, inevitably bringing about its destruction.