I consider the symbiotic or endosymbiotic hypothesis of the origin of mitochondria to be more convincing. She is more like the truth. Yes, and there is a living example of this: the symbiosis between algae and ciliates. Moreover, mitochondria have their own DNA and the ability to form their own proteins. This suggests that this organelle used to be, most likely, a separate cell. And perhaps there was a symbiosis of her with another cell, subsequently, she became part of the cytoplasm, that is, organelle.
Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.