Okay, fine, I can think of a dozen counterexamples for both categories, too – but, in general, green fruit isn’t ripe yet, but green veggies are. Is it just about sugar content? Corn, bell peppers – both of which do turn other colors when ripe – carrots, etc., tend to be sweeter than, say, string beans or lettuce.
What’s the deal?
Well, lettuce is just leaves. It’s not a seed pod or an ovum or anything. Actually, we eat most vegetables at a time when, if you asked the plant its opinion, they aren’t ripe yet, reproductively speaking. If you want to save seeds, you have to let some of those zucchini grow to be garden submarines. Mature cucumbers are woody and pretty much inedible. Leafy vegetables are usually bitter once they bolt and go to seed.
:smack: on the whole leaves vs. seed pods thing. So, yeah, we can exclude lettuce, cabbage, and the like.
But it still begs the question – why do we eat veggies green (even if that means they’re “unripe” from a reproductive point of view) and not fruits?
Because fruits don’t taste good until they’re ripe. The plant doesn’t want you to eat them until it’s ready to have the seeds dispersed, so the fruit only gets it’s full dosage of sugar and such when it’s ready. Veggies, on the other hand, tend to be more tender before they are mature - so it’s better to eat them then.
I know I’m coming across as a complete idiot here – but if there’s an evolutionary advantage to fruits to making themselves better-tasting when the seeds are ready [and, yeah, I’m not talking consciousness or intentionality here, but you know what I mean], why doesn’t that apply to veggies?
Generally you aren’t eating the seeds of the veggies. You’re eating the stem, leaves, root, etc. Second, different plants have different methods of seed dispersal. Fruit producing plants came along fairly late in the game, so lots of plants were already doing fine just using wind or whatever. If those plants are doing well with that method, then they aren’t going to bother making themselves tasty to animals - remember that creating fruit takes a huge amount of energy and nutrients out of the plant, so it’s not an easy thing to do or something the plant would want to do if it didn’t have to.
Botanically, a fruit is defined by the flesh that surrounds the seed of a flowering plant. So plants want their fruits to be eaten (for seed dispersal).
A vegetable is any other part of the plant - it doesn’t do the plant any good if you eat its leaves or roots.
And yes, green peppers are fruits that taste good green. And tomatoes are fruits, so they’re not a counter-example - they’re not ripe green.
Yeah, I deliberately left tomatoes out of the OP, because I realize they’re fruits.
What about, say, string beans? You’re eating the pod there – is there a botanical difference between a pod and a fruit? is there a fruit or fruit equivalent in a string bean?
Also, cucumbers, and other squashy and gourdy type veggies – are those not fruits?
I think you’re having trouble here because you’re drawing a culinary distinction and asking a botanical question.
It just simply isn’t true that “vegatables” taste better green and “Fruits” taste better other colors if you use the botanical definitions. Zucchini, squashes, green beans, tomatoes and green peppers are all technically fruits we eat unripe by the plant’s standards. I think we call them vegetables culinarilly *because *they are unripe and therefore not sweet. Beets, carrots, rutabegas, red onions and red cabbage are all vegetables (both botanically and culinarily) we eat ripe and colorful.
Anything surrounding a seed = fruit
any non seed bearing part of a plant = vegetable
clarification: of course, we eat both unripe and ripe tomatoes.
Ah, okay, that actually helps quite a bit.
Thank you.
The distinction here is between fruits which are evolved to be dispersed by animals, and those which are not, but which we eat anyway because we have selectively bred them to be edible. It is also necessary to look at the ancestral forms, rather than the horticultural varieties, which may be very different in color and nutritional content.
Fruits which originally evolved to have their seeds dispersed by animals include apples, pears, peaches, plums, oranges, cherries, tomatoes, chilis, etc. The ancestral forms turned bright colors when ripe to indicate to animals that they were ready to eat. Some horticultural forms - e.g. Granny Smith apples and green peppers - remain green even when “'ripe”.
The ancestral forms of string beans, snow peas, etc, were not dispersed by animals. The pods simply opened and released the seeds. We have bred these forms to have edible pods, which we eat seeds and all. In regular peas, beans, etc, we discard the pods.
The ancestral forms of gourds, pumpkins, zucchinis, etc, had animal dispersed seeds, and I think all turned bright colors when ripe. Cucumbers we eat unripe; they turn yellowish when ripe.
As others have said, other vegetables are plant parts that the plant does not “want” us to eat, so there is no reason for them to change color.
Thanks, Colibri – I was hoping to lure you in here.
Pfft. Luring Colibri’s easy. You just hide and imitate the song of a dusky seaside sparrow. He’ll break his legs running in to document it… 
Laugh if you must, but I have a horrendous DoperCrush on Colibri.
warbles experimentally
That’s why I hang out here - because of all the groupies. 
When an orange gets eaten, it ensures the seeds are dispersed which helps propogate the next generation. There is an evolutionary advantage in shouting out to any animals “look at me, i’m ripe and tasty, please eat me”
When a cabbage gets eaten, it dies. It has an evolutionary advantage in NOT looking attractive to animals.
A related note: my psych professor put forth the theory that we evolved the ability to see in color so that we could distinguish ripe from unripe fruit. Is there evidence to buttres this theory–e.g., do we have non-fruit-eating close ancestors that can’t see color?
Daniel
I’m pretty sure primates have much more color sensitivity than other mammals. Cats and dogs and horses aren’t strictly color blind, but they aren’t nearly as color sensitive as humans. And yes, this is likely because primates eat a lot more fruit than most other mammals.
Why are radishes and beets brightly colored, then? By accident? By human design?