The increase of human population on Earth was a major problem during the first three centuries of the third millennium.
During the twenty-first century this increase was slowed somewhat by the crisis created by the ending of the oil supplies. The quick shift to a nuclear power economy averted the crisis and population continued growing at a reasonable rate.
In the twenty-second century serious advances in allotransplantation were made, almost completely eliminating the risks of transplant rejection. This allowed humans to live longer, as long as there was a large enough supply of organs. Without the technology to mass produce organs, many nations began re-adopting the death penalty and slowly extending it to more and more crimes. Executions started being done in hospitals instead of prisons in order to harvest the criminal’s organs.
During this period the colonization of space started to look like an attractive solution to the overpopulation problem, leading to the foundation of the Space Colonization Consortium. However, the Consortium’s efforts to establish a colony on Mars proved too slow to solve this problem.
Soon after Earth’s population reached 20 thousand million in 2275, the Fertility Laws were enacted to keep population growth in check. Long-term contraceptives became mandatory to everyone older than 13. Everyone without a genetic defect had one birthright, a right to procreate. A couple could give up both of their birthrights to stop taking the mandatory contraceptives and have a child. These laws, together with the small supply of organs, managed to slow down population growth, and eventually stabilizing it at 18 thousand million by the 25th century.
With the construction of the first Bussard ramjet by the mid-23rd century, the establishment of a colony outside the Sol system became a possibility. A large generational colony ship named Adam was built and launched by 2284, with one million people aboard. More colony ships were launched in the following centuries.
The discovery of the beimini drug could have brought the overpopulation problem back, by solving the organ bank problem. However, the construction of a safe ramjet ship twenty years later made emigration to extra-solar colonies a possibility, reducing the impact of the drug in population growth.