The problem with lowering the population is that it would lead to slowing technical progress as well. The fewer humans we have the fewer high-IQ humans are born

The problem with lowering the population is that it would lead to slowing technical progress as well. The fewer humans we have the fewer high-IQ humans are born, the less is advance in science and technology. One of the major benefits of space colonization is to increase human population so that it produces more high-IQ people that can keep advancing humanity. All that progress in the last 200 years can be attributed to larger amount of high-IQ people born which is a direct consequence of total population growth. Stopping growing population would lead to stagnation in technical progress.