April 20th, 2010 - January 7th, 2151 - These years marked a struggle for survival by the remaining civilian population and a similarly futile struggle against the alien invaders by a resistance movement made up of a scattered handful of hidden military bases. A long, cold nuclear winter followed the disastrous events of April 20th, 2010. With large swathes of the Earth covered in deadly radiation and the sun hidden behind a cloud of smoke and fine particulates that cast a pallor over the land, it was extremely difficult for the isolated population pockets to eke out a subsistence living. Temperatures plunged below freezing even in the summer, so what little fertile land remained radiation free was covered with frost bitten crops and shallow graves filled with the gaunt bodies of those who succumbed to starvation. While the Oozyxphg for the most part went back to ignoring humanity while they proceeded to methodically strip the Earth of her resources, they did act with terrifying force whenever they uncovered one of the secret military bases that continued to search for a means to defeat the aliens. As the years turned into decades, humankind came perilously close to extinction. Scattered bands of hunter gatherers chased herds of elk and deer across the frosty landscape, scavenging canned goods from the eerily quiet ruins of cities rendered empty in a split second by the neutron bombs of the aliens. However, humans are marvelously adaptive animals and soon they began to increase in numbers again. Even though they had lost most of the knowledge of their forefathers, their innate cleverness and drive to survive stood them in good stead and a new, tribal society began to develop.
The resistance movement: While the majority of the human survivors devolved into a stone-age level struggle for survival, the hidden military bases advanced scientific understanding in leaps and bounds by reverse engineering Oozyxphg technology. Most of the truly brilliant scientific minds had been safely sequestered by their respective governments well before the fateful day that saw humankind brought to its knees, and these scientists feverishly worked to understand the principles behind forcefields, organic computers, wormholes, and a whole host of other alien innovations. Soon, the force-field generating tissue utilized by the Oozies had been successfully cultured and military vehicles were outfitted with portable force-field generators. Military robots were constructed based on the secrets gleaned from the Oozies imposing robotic suits. Captured aliens were subjected to all manner of testing in an effort to create a biological agent effective against an alien immune system. The foot-soldiers of the resistance chaffed under the knowledge that while they sat well fed in underground bunkers, enjoying the latest advancements in holographic technology (holodecks ain't just for Star Trek, baby!), their civilian counterparts were scrapping for their very survival on the surface. Only the belief that they represented the best chance to defeat the alien invaders once and for all and restore humanities position of dominance on the planet through their carefully safeguarded technology kept the resistance movement going for almost 150 years.
The Oozyxphg: During these years, the Oozies finished their major excavations for mineral wealth on land and began the long process of vaporizing the oceans and collecting its dissolved mineral bounty. They constructed immense machines that automated this process, and the result was a drastic increase of evaporated water in the atmosphere, and consequently, increased rainfall across the world. This eventually led to the end of the nuclear winter and, combined with the tremendous amount of greenhouse gases released in the raging fires that followed the nuclear detonations, precipitated a dramatic period of global warming. Many low-lying areas became vast swamps as the perpetual rains generated by the alien machinery continued to fall. Many species that had survived the alien neutron bombs and the errant nuclear armaments went extinct during the rapid climate shifts in the century following the first apocalypse. The Oozyxphg paid no heed, continuing their single-minded pillaging of all the mineral wealth that had ever been washed out of the earth by millennia of erosion and rainfall and swept into the oceans.
January 7th, 2151 - A fleeting victory was achieved. The biochemists in the resistance movement had finally created a biological weapon that was highly contagious, air borne, could survive for days without a host, and was nearly 100% lethal to Oozyzphg and harmless to humans. Large quantities of the virus, codenamed FDF7, were produced and simultaneously released near a score of Oozyxphg operations. Successful beyond even the wildest dreams of the resistance movement, FDF7 not only resulted in the rapid decimation of the Oozyxphg on Earth, it traveled through the wormholes to the Oozyxphg homeworld. The few aliens who did not succumb to the virus were so weakened that they put up little resistance as they were hunted down and destroyed. Earth was once again ruled by the human race.
January 7th, 2151 - June 16th, 2156 - These years marked a brief resurgence of human culture, as the resistance movement joined the civilian survivors and shared their knowledge of technology with the now primitive tribes of hunter-gatherers they found roaming the world. Some of the long abandoned cities, which had become the subject of elaborate mythologies among the tribesmen, were repopulated. The human population exploded as birthrates skyrocketed, driven by the suddenly abundant food sources made available by the incredible technology that the resistance movement had developed over the years.
June 16th - July 1st, 2156 - The Second Apocalypse.
Sometime around the middle of June, 2156, the FDF7 virus began to mutate rapidly. Whether this was simply a chance occurrence or if it was a side-effect of the alien gene sequences that had been inserted into the virus is unknown, but the results were deadly. The virus soon infected all living organisms, plant and animal, on Earth. For most, it was fatal. For the survivors, it had the peculiar effect of causing rapid alterations in their genome. Strange mutations arose, and while the mutations themselves were not passed on to the offspring of the mutants, the virus was passed on from mother to child and newborn children also exhibited the bizarre mutations. Plants, animals, and insects alike passed through the equivalent of thousands of years of evolution in several short lifetimes as the mutations caused a bewildering variety of new species to arise. Some plants even achieved sentience, and over time, societies of mutant plants and animals came to share the Earth with mutant humans. Only a select few incredibly healthy humans proved resistant to the mutated virus, and their descendants shared their immunity.
And that, folks, is how you get to the Mutant Future of today (hundreds of years later, of course)!