Ten thousand years after Doomsday the Earth was a very different place from what the pre-doomers had exploited, and then destroyed. Nature has her ways, and some of them are inexorable, even if they are sometimes slow by human standards. Climate shifts have quite a few factors which affect them, but the Doomsday H-bombs were quite different. They were sudden, and created rapid global cooling at a time when everyone was worried about global warming. With the dust in the air over the Earth, and especially the northern latitudes, there had been an accumulation of snow. Years later when the dust had finally settled out there was once again a layer of snow all over the north which hadn’t totally melted each year with the coming of spring. Over the years this had accumulated, and after these many years the cooling effect had totally shifted the climate towards colder, but with more rapid shifts from summer to winter conditions. This had changed what plants would thrive, which in turn changed what animals could survive and what crops could be planted.
In general it was bad for humans because it made everything more unpredictable, which had forced populations to be much smaller to cope with the shortfalls in the lean years. Of course humans are much more adaptable than all other species so they were surviving where others were not. The climate led to an ecosystem of only species that were able to survive rapid swings of temperature. Those species with wide-ranging habits did better than more fixed ones and migratory birds and animals did better than those who liked to maintain fixed homes. Some trees that had survived because of the Lifehavens had done well at first but when these new more variable conditions started to prevail they failed. Now the world was populated by greater numbers of a given species at any particular spot, but with fewer species being there. Similar to farms with a few monocultures.
The humans were a special case: because of their intelligence and sociability, they had regained a sustainable lifestyle after ten years and after one hundred were doing quite well again, even if their population was tiny compared to pre-Doomsday standards. For the next several hundred years the Earth was a paradise, because there was an abundance of everything humans would need. And, the earlier civilization had left a wealth of entertainment, and knowledge encapsulated for their easy consumption. Because population controls were enforced on a fair basis the population fitted the environment, and one thousand years after Doomsday the population was quite large at one hundred million people, and thriving. People everywhere accepted the population restrictions because they felt that they were fair and justly applied. There had been a policy of encouraging people to move freely about the planet, and so religion, politics, and group identity were homogenized, and because everyone was so interconnected the problems that any particular person had were problems which concerned everyone. So the problems and the expenses of the solutions were born equally by all the people.
There had been some people that wanted to be in close association with others for some particular reason or another, but so long as anyone could join in or leave any particular group there hadn’t been any sustained problems. That is the way it was for a quite a long time, and it worked because there was always an abundance of necessities for everyone, or at least a sufficiency during bad times. With the realization that the climate was growing more difficult there was a referendum to reduce the world’s human population. This was to be done by limiting some random proportion of mothers to a single child guaranteed instead of two as was usual, but they could petition for a second baby. In this way there could be a slow, and orderly reduction of world population.
Somehow — no one seemed to know quite why — people grew increasingly disaffected with the way things were being done, and this birth control allocation seemed to be the most contentious. It seemed that some people identified with some particular genetic strain, and felt that they were being discriminated against, and saw this as a first step toward extermination of their group. When world genetic homogenization was in full swing this problem hadn’t been serious, but now it seemed almost everyone was upset.
Then it happened – people separated into groups situated on particular pieces of property, and were willing to defend that place against all outsiders. Also, they set up their own new laws. They quickly found that if their population was greater than their enemy’s that they had an advantage. Thus, there began a worldwide population explosion with each group trying to out reproduce all the others. It was baby madness, some people said. It would produce a population race like the ones of the past eons which were by now ancient history. But everyone agreed that things were different now, and that wouldn’t happen. We all knew better now, and the immediate problem was to outbreed the folks over on the other side of the hill, or wherever they were. Of course they soon needed weapons, and then better weapons, and because the historical archives were available to everyone the weapons race was very rapid. All sorts of cooler heads tried to stop the ugly direction things were going but to no avail. Well, mayhem proceeded in much the same order it had in the pre-Doomsday times, but much more rapidly, and with the same awful results.
This seems to be nature’s cruel joke. Outbreed your competitors, and let the survivors outbreed their competitors until the end of time. For a short period humans had overridden that natural driving force, or thought they had, but then it came back, again and again. Human intelligence, and sociability had time and again brought about this horrible end to their struggles. After ten thousand years the only method for maintaining calm for very long was to have an agreed upon population limit imposed by orderly human laws rather than nature’s laws. Humans in their natural state cycle endlessly through boom and bust. Unfortunately, in this case, nature’s laws are stronger than man’s.