Genetic engineering.

The thinking part of the brain makes up only a very small area of the frontal lobe. We don't even have much control over the are used for language. In evolutionary terms we are still very much inferior savage beasts who just tramped out of the jungle. A very large portion of humanity are still inferior and this percentage is increasing as technological improvement overtakes natural selection. We won't run low on our genetic resources for a while however as evolution takes 10000s of years and we've only just come out of a period where 50% of people died before the age of 20. However when 99.9% of people survive and reproduce the passing on of inferior genes accelerates to the same rate at which animals can be bred for different properties. In this case whatever property allows people to reproduce the most which could be the property of being more likely to have illegitimate children or be a tyrany and impregnate vast number of the women you are oppressing. Neither are desirable.

There are of course more direct benefits of selecting embryos without genetic diseases and designer babies, however these are a given. People will be using these once the technology becomes available and little effort is needed to ensure enormous amount of sufferring are prevented by their employment.

However however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however however.