Let's suppose that medical science can stay ahead of communicable diseases through antibiotics, antivirals and immunizations.
Let's suppose that medical science makes similar progress in addressing diabetes, heart disease, cancer and auto-immune syndromes.
Now, assume two populations.
One population is slowly declining and responds bystarts into cities where services and amenities are readily available. While the net population is dropping, the population density as experienced by most residents increases. The average age goes up. In order to maintain the first population's quality of life it becomes necessary to import many people from the second population.
|The first population is intimately interlaced with elements of the second population. Photo by Kurt Freihauf.
The second population is not stagnant and doubles every twenty-to-thirty years. Competition for resources causes warfare, both low level and 'hot'. The resulting strife causes farmers to not work their fields. Hunger, migration and refugee camps result. Population continues to grow and the effective population density skyrockets as entire families live in tents a scant two meters apart.
Certain types of cancer are difficult to treat. That is not because there are not effective chemotherapy agents. Rather, it is because the cells or tumors are difficult to penetrate and it is impossible to raise the levels of the chemotherapy agent to therapeutic levels.
So even if medical science were able to miraculously subdue pestilence, the other three horses of the apocalypse would ensure the victory is only on paper.
Epidemics have not been vanquished and the longer the periods between episodes, the larger the pile of U235 will be when it lights-off.