Here is a fun fertility fact!
It is known that natural ttc planning became widely prevalent in the 1970s. This is when much of the research and many of the related clinical trials took place. However, it is interesting to note that anthropologists have learned that there were also 3 Kenya tribes; the Taita, Kamba and Luo and one Aboriginal tribe, the Niranji, who taught the young women in their communities to use the changes in their cervical mucus to identify fertile times in their cycles.
It would be fun to know all the ttc tricks that women from all over the world have used over time! That could be quite a wonderful resource!