Welcome to Earth, year 2450.
It had happened, the inevitable. WW3 turned nuclear. The largest and most powerful countries in the world had wreaked havoc on each other, for little gain. They poisoned the Earth, pouring vast amounts of nuclear wast everywhere, they no longer cared, the planet was done for anyway by now. Over the few years that followed the end of the war, strange clouds built up everywhere, poisoning the land and everything on it. After that, the world changed.
Things happened, things that shook the world so badly that the surface was no longer recognizable anymore. The inhabitants too, changed. Billions had died in the war, billions more from the poison cloud. Those that survived that mutated, billions more died from their mutations in the years that followed. There is now hardly a fraction of the worlds population left now, and they're still changing. The ones that survived their mutations had often found their new acquired skills useful, and became superior. The same was happening to the animals, plants and fungi. Thousands and millions of species became extinct forever. There are now less than 3000 species left, if you can call them that, for there was much variation in each. They bred, passing on their genes to their offspring. Eventually the world settled down
Decades, centuries, have passed now, and the scattered populations have been drawing together for the last 100 years, slowly, finding each other on this new world. Hierarchies came out, the superior dominating the inferior. They found comfort at being together, especially with those most like them, forming clans in the environments each were best suited to.
Welcome to earth, year 3500.
The fight for survival is on. How will you fare?