>>17866171 (OP)There are various tribal societies where virtually all men have sexual relations with children, and surveys of societies in large datasets show that the average age of marriage in most societies would be considered "child marriage" by modern feminist standards, but as far as civilizations go, I would guess that sex with children was most common in Rome. Pre-pubescent marriages were common in Rome, and marriages were generally consummated immediately.
https://www.tandfonline.com/doi/abs/10.1080/00324728.1965.10405456
Pederasty was also common in Rome, and unlike in Greece, it often involved pre-pubescent boys, but it became disdained towards the late Roman empire. Child prostitution involving children of both genders was common.
Sex with children also happened in India, China, the Muslim world, Japan, etc. A lot of information on this subject is hard to come by, because unlike with other sexual proclivities, like homosexuality, there hasn't been a large, funded effort to collect and present information relating to the subject. There are no Wikipedia articles titled "Paedophilia in ancient Rome", or "Adult-Child sex in Indian civilization", like there are with homosexuality and transvestism, despite being far more common. In fact, you would be permanently banned from Wikipedia if you attempted to write such an article, because writing a completely unbiased, descriptive account of such matters is viewed as advocacy. History is constructed according to the biases of the people writing about it.