I suspect the question reveals a blind spot in perspective. Food, by its very nature, is dangerous and fights back. Modern society insulates us from this risk

I suspect the question reveals a blind spot in perspective. Food, by its very nature, is dangerous and fights back. Modern society insulates us from this risk; with a secure, safe, food supply, risking one's life to try something new seems insane and it's hard to imagine enough people have ever done it to learn significant secrets and what would be the point anyway? If the food supply is neither secure nor safe, risking one's life to give the community a new option seems much more reasonable and even heroic, and an area in which people would try extreme things for a shot at glory. Do people get injured or even killed hunting wild game? Of course. That's expected, and it's just how you get food. Do people get injured or even killed learning the secrets of wild plants? I would expect that's expected, too. So my suspicion is that this question is a lot like asking, "How did 18th century humans learn to defeat smallpox?" Well. It was hard. And the stakes were high. And a lot of people died while we tried stuff that didn't work. But in the end, humans are brave and resourceful especially when the need is great.