Is it decided that the UN secretary general be old-aged man?

All the previous secretary generals of the UN are male and old-aged. Is it decided that the secretary be male and old-aged?

It is true that old-aged people may have rich experiences and their decision may be after assessing the impacts and consequences of their decisions. It is true that old-aged people may not decide emotionally without consultation. But their mental power to generate new and better ideas that bring about a better world to may not compete with those of the middle-aged people. So, which one is better? I think, we need change, we need a better world and that requires new ideas and new concept that changes not only the socio-economic system of the world but also the geo-ecologic system of our planet.

The second point is why not women be elected as secretary general of the UN? There are two concepts in ethics; Justice and caring. Men are mostly justice ethically; that means their thinking is about the current benefit. They argue that people today must be in better position than what comes tomorrow. On the other hand, women’s ethical thinking is caring which considers and worries about the coming generation and the greening of the world. Whether to choose the justice or caring mentality can be an issue and left for debate. But I never hear women proposed as candidates for secretary general of the UN. Why is that?