And they goofed up. People now consume plant based drugs like caffeine, cocain, nicotine, THC, pyote, 'shrooms, and so on. These are all poisons. Also, aspirin is based on a poison. Most drugs are based on plants. I'm including mushrooms because those would be discovered the same way.
All plants make toxins, they don't want to be eaten (ripe fruit aside), most of us are pretty good at detoxifying the plants we consider food, but still some people overdose
on vegetables. That kale guy who ate kale smoothies, kale salads, charred kale, and nearly nothing else wound up in hospital having exceeded the dangerous dose
It's a shame that safe limits are not commonly available for everyday plant based food - two bags of vege chips is enough to make many people quite sick, but it won't tell you on the package.
The trouble is there are dangerous or even lethal amounts of practically every vegetable, but it's nearly impossible to find the numbers.
The only advice is to have great variety, and don't eat stuff with an ingredients list, but that's also hard to do
I went a tad extreme since I'm allergic to several of the staple plant foods (notably all the grasses, wheat in my food makes me sick, bamboo in my clothes makes me itch) so I quit all plants (and I haven't died of scurvy even once!). I still wonder what is the LD50 for cabbage.