This might have an obvious answer that I've missed but I'm just checking it out for a fanfiction. I know kekkei genkai are genetic. I know everyone has chakra but not everyone has the ability to use it and this may or may not have something to not with the size of chakra coils? Not sure about this as I've probably read more fanfics than canon. Anyway. The question is this: Is the ability to use chakra genetic (so basically all ninja are descended in some way from Kaguya Otsutsuki including Sakura Haruno via some kind of recessive gene..) or was it simply available to use (randomly?) after Kaguya ate the fruit of the Shinju? Since Kaguya is named as the progenitor of chakra, I'm assuming no one could use chakra before her. The genetic theory requires a long period of natural selection, such as the Out of Africa and Eve theories on Earth. I'm not sure of the time skip between Kaguya and Naruto is enough for this. Anyway, all answers welcome.
The only people who were born with chakra are Kaguya's descendants. However, people got their chakra from the Rikudō Sennin when he created ninshū to make people connect to each other.