I.e Food A is toxic and we don't know how to treat it. Food B is toxic and we know it takes n-1 steps to make safe. Someone comes along and applies n-1 steps to Food A and its still toxic. Someone else comes along and applies n-1 and then an nth step and there's progress.
But yeah, the article does not come near to examining the way cultures discover things nor in general nor in the case of the cassava.
The article even says that the natives had no idea why they were getting sick! How did they connect the "can't use legs" to the cassava they ate?
Again, I realize that it must have been the way you describe, but it's still amazing.
> How did they connect the "can't use legs" to the cassava they ate?
Keep in mind these people are in Africa cassava is native in South America. I am pretty sure people in south America will tell you that cassava is toxic if you don't do all the steps and not just "it's our culture".
The it's our culture response might be the case in places where it was introduced and people were told you have to do x,y,z to eat it.
The people getting sick are in eastern Africa, while cassava is native to South America. Stands to reason that the methods of cassava preparation weren't as ingrained to the people who were getting sick.