Why were all the Shenzhou VII astronauts born in 1966?

Coincidentally, it takes about 10 years from ordinary pilots to excellent pilots, and then it takes at least 10 years to train a qualified astronaut from excellent pilots. Their generation of astronauts happened to be born in about 66 years. Yang Liwei said in answer to Bai yesterday that the second generation of astronauts are being selected. They may be younger than the first generation. Because there are successful experiences and methods in training astronauts and there are shortcuts for reference, they will be 30-35 years old when they can perform space missions, instead of 35-42 years old like Yang Liwei, and their technology is improving! ! !