Birth control is one of the most divisive issues in public policy, especially where it involves abortion. There are, I think, at least two reasons for this. First, it deals directly with one of the most important and personal decisions people can make, whether to bring a child into the world who will carry their genes into the future, and the question of who else can share that decision. Second, it brings into the focus the related questions of when a life begins, and when that life should be subject to protections against murder.
For most of human existence, these decisions were made in the context of the survival of the group that a person belonged to. Mating was sanctioned by the group, as it is still done by many families. As in much of the rest of Nature, the weak were killed or allowed to die as infants so the strongest could help improve the group's survival rate, and the birth rate was “controlled” by doing the same with the naturally higher number of females born. These methods primarily enabled a population to avoid extinction from overconsumption of available resources.
With civilization came the ability to access more resources on demand, enabled by technologies that enabled individuals to have more control over their destinies. As a result, the overall population began to grow as the birth rate grew and the death rate (which included infanticide) dropped. Value systems developed that promoted these trends, first in groups and then in governments, which assumed increasing responsibility for maintaining order as people became less personally involved in each other's lives. In the decreasing number of situations where increasing population could imperil people, the new values necessitated more humane methods of birth control; these were aided by both physical technologies (such as contraception) and cultural technologies (such as education and government mandates).
Demographers have noted that birth rates tend to fall as women become more economically empowered, which occurs in affluent societies such as the United States. My analysis of happiness shows that the world population's growth rate (essentially the difference of the birth rate and death rate) is nearly proportional to happiness, with an interesting difference: it stopped speeding up soon after happiness was twice the minimum happiness (in 1875), it stopped increasing by the time happiness was three times the minimum happiness (in 2008), and it will likely fall to zero relatively soon thereafter, in 2021. The apparent statistical correlation between happiness and population growth rate is consistent with the demographers' appraisal, and adds to the plausibility of a biological failsafe mechanism, like I described in the last post, which keeps our population from growing too large for our resource base.
Unfortunately, without leveling off our consumption and compensating for our resource depletion, it may be too late to avoid an increase in the death rate – the last recourse in population control, which our ancestors used effectively in much more limited environments – as the final braking effort that becomes dominant after the peak and during the crash.