Somewhere in his thesis Growing Up Sexually, Diederik Janssen describes how the study of the normal sexual development of children came to an abrupt halt in English-speaking countries around 1980, with other nations following after a few years' lag. After that, the study of sexual activity by minors would only be approved if the researcher promised to do it from the point of view that sexual activity by minors was something that needed to be stopped. There was no normal sexuality of children, it was all pathological. So yeah, there are lots of questions that need to be answered, and they aren't going to be answered any time soon. The universities and other institutions that should study this are not going to do it - they know that they would risk having their funding yanked.
source: 'Forbidden questions' by 'Dr. Boylove'; secure.boychat.org/messages/1393552.htm; BoyChat; 9 May 2014