[whyenot]

> many plants have toxins in them to prevent animals eating them

Almost all of the plants humans eat have been domesticated and bred to no longer produce these compounds in the parts that we eat. For other plant parts, such as fruit, being full of sugar and tasty is an adaptation because it helps with dispersing the plant's seeds. If this is something that interests you I recommend reading 'With Bitter Herbs they shall eat it: Chemical ecology and the origins of human diet and medicine.' by Timothy Johns. It was published 30 years ago and is essentially his PhD dissertation but quite readable and still one of the best resources on this subject.