The ways the aliens do hybridizations change with time. Many of them have very advanced gene manipulation technologies, but not many of them have understanding of humans. Contrary to common belief they don't read human minds and have very little understanding of human ways of life. Therefore their early hybridisation efforts were traumatic to many humans. In the last 20 years their knowledge of humans improved and now the interactions with the aliens are often happy. Since 2014, the hybridizations are done on a voluntary basis with informed consent from volunteers. Yet, the prime directive is still in place and the hybridization program and developing contacts are known only to small circles of people.