Question

In
China, they tried to limit every family to having only one child. What are some
problems that you think would happen (or did happen) if this kind of law were
put into place?

Answer 1

A consequence of child limitation regulations is a significant reduction in genetic variety, i.e. bottleneck effect. If China continues this, future generations will more than likely exhibit mutations and/or less genetic resistance/superiority as a population due to limiting factors, e.g. diseases.

Unless they go interracial! Whoo! :)

Answer 2

@Cardinal_Carlo This is not a significant reduction in population to cause a bottleneck event, even if it went on for hundreds of years. We have a tiny effective population size (the minimum number of individuals needed contain all the genetic diversity of a population). The most I could find was on the order of tens of thousands.

This means that the Chinese would, statistically speaking, need to be reduced lower than the above effective population size before a bottleneck effect could happen.

@beautykillzz The real effect was social. Males are favored over females, particularly in rural areas. That should give you a start, but just search google.