In order to combat the shrinking population, person-on-person violence has been banned completely on all fronts, and death-defying hobbies have been taxed to the point of being extinguished. Prisons and jails have been turned into baby farms, under the pretext that stronger and more vicious men are more likely to have more resilient sperm.
To fill the void of settling disputes, the government initially turned toward government-sponsored MMORPGs, but this encouraged slovenly behavior among the dwindling populace, and after a few years, was reduced to being used exclusively at the baby farms, to rehabilitate the adults and provide an educational system for their offspring.
After the failure of the MMOs, the government offered a reward to think-tanks and individuals who could come up with a suitable solution.
In the meantime, with the human population of the Earth sharply dwindling, many countries found themselves holding an excess of computer processing power. Instead of allowing it to go to waste, or dismantling the server systems, they leased out the processing cycles to scientists and think-tanks to perform large distributed computations.
One group using China's servers discovered a break into human pheromone production, re-enabling the human vomeronasal organ, and making it possible to inject a synthesized drug into animals to cause them to treat the human who injected them as alpha.
This world is Earth in the early 3000s AD.
Technology advanced steadily through the first half of the last millennia, but in the latter, the destruction we've wreaked on our planet has caused scientists to change their focus to sustaining our existence rather than improving our lifestyle.
3D printers exist and are as accessible to the general public as personal computers were in the 1990s. Chemical synthesizer kits (commonly called synth-kits) are common enough that regulations on drugs are rarely enforced (though drugs laws have not been repealed).
While the human population has shrunk, non-human populations around the world have spiked, bringing wild animals regularly encroaching on human-claimed territory, and this only increases every year.
With the general overall failing of human reproductive organs, contraceptives are all but non-existent, and women who successfully become pregnant are given tax incentives and borderline palatial housing (by government standards) for the duration of their child-rearing. They are also given access to the educational and recreational MMOs.
For the rest of the human race, anybody who can afford a synth kit and a simple DNA test (easily 75% of the population) sets about collecting and training a team of animal bodyguards to protect them from the still wild animals and other humans who strive to do the same.