Answer:
changes in human genetic characteristics
Explanation:
Since the Flynn effect sees the increase in IQ scores with factors directly impacting: changing communicating technologies- This means people are engaged in more intellectually demanding activities in the context of learning, updating and managing information.
Similarly, with increased opportunities for educating, learning comes at the hands of most people, and this enables a general population to become more skills in scoring a higher IQ.
Other development factors, like having better nutrition, will account for brain development and will lead to manifest as people more capable of dealing with abstract reasoning. If the reduction in family size coincides with having a better quality of life, then people are expected to become more proficient and score higher.
The changes in human genetic characteristics are the least related since normally the changes in genetics last too many time frames and they are not the focus of interest that the Flynn effect can measure. The rest of the options can be traced during a lifetime.