Yaoi history

I was interested in this particular question:
What was the first ever “yaoi” manga?
So far I got basic facts like how it first showed up in the 1970s as a sub genre of shoujo, and how the word yaoi was an acronym for yama nashi, ochi nashi, imi nashi (no climax, no point, and no meaning). With all of this, the earliest one that I could find was Captain Tsubasa, which was made in the 1980’s. Is there any yaoi that is older than that one? I still don’t even know if it counts as yaoi or not...