Across a thousand years, it starts becoming likely.
Biff: "Didn't you know you're not supposed to eat Cassava?"
Awk: "No. What's the problem? I did a couple weeks ago, and I'm fine."
Biff: "It's deadly. What did you do?"
Awk: "I mixed the paste with water to make dumplings, then Thag came by wanting to show me his new club. So I let it sit in the shade for the afternoon."
Biff: "Interesting. Let's try that again and feed it to Grep and see what happens."
Ah, but you miss the point - whether you leave it to sit for an afternoon or not, as long as it's cooked you'll be fine. Unless you do it for a significant portion of your food - and Cavassa's pretty easy to grow, so it'd make for a nice staple crop - in which case you'll die after a few years.
So the feedback loop isn't "weeks" it's "years" or "decades".
"Fine" given that you eat such foods rarely and/or your time horizon is months not years. No immediately apparent health effects, but long term ones - sort of like eating fish high in mercury.
Across a thousand years, it starts becoming likely.
Biff: "Didn't you know you're not supposed to eat Cassava?"
Awk: "No. What's the problem? I did a couple weeks ago, and I'm fine."
Biff: "It's deadly. What did you do?"
Awk: "I mixed the paste with water to make dumplings, then Thag came by wanting to show me his new club. So I let it sit in the shade for the afternoon."
Biff: "Interesting. Let's try that again and feed it to Grep and see what happens."