Wheat was one of the vegetables that were first grown
Raised like this, the question may sound strange, but have you ever asked it? It is so assumed and widespread that eating vegetables is something natural and of course, healthy, that wondering whether we should eat vegetables or not may seem ridiculous. It is not at all. As always, nothing makes sense in biology if it is not in the light of evolution.
Let's look at vegetables from an evolutionary point of view. To start, they don't move. Obvious. But why don't they move "too much"? Basically because they don't need to do it. Everything they need to develop, grow and reproduce can be obtained directly. Sun, water and soil nutrients. Moreover, those plants in which we can observe with the naked eye, movement, does it precisely to supply a lack of nutrients obtained from animals. Are the carnivorous plants.
Since a plant has everything it needs to live, does it need to be food? Absolutely. It's more, if something worries plants is that they be eaten by other animals. Thorns, poisons, shells ... plants have developed all kinds of defenses so that they are not eaten by living beings who do not know how to live from the sun and who have to move to feed.
There are, of course, exceptions to this general rule, such as fruits or nectar. Products specifically selected to be eaten and thus spread the seeds by animals. An extreme example of this is the yew (Taxus Baccata) whose leaves are toxic, and its edible fruits. The plant decided that it needed the animals to reproduce, but took care that they ate their leaves.
The co-evolution between plants and animals was developing an armentistic war between the two. Some opted for "chemical warfare" becoming toxic, and others for physical methods, thorns and shells.The acacia, an example of an arms race with the Giraffe
Herbivores and herbaceous species
At a time in the history of the earth the herbaceous species appeared, and with them a series of animals evolved, which together with bacteria from their digestive tubes, were able to use them as food. When a cow eats grass, it does not feed on the grass, but on a broth of bacteria that have digested this herb.
Similarly, other groups of animals "won" the battle against some plants and developed mechanisms to feed on certain parts, such as seeds, which in principle should not be eaten. For example, the granivorous birds. A plant, in general, is not interested in eating its future offspring. Remember that in a fruit, we eat the pulp, but the seeds are intact and both parts benefit.
The human being
For millions of years, the primates ate fruits and vegetables almost exclusively, as gorillas do now. Hence its huge guts with its huge digestive tubes to digest cellulose.
Now, at one point, and for various reasons, certain primates evolved into hominids and in that evolution, they changed their diet dramatically. Along with that change of diet, and quite possibly for this reason, their brains began to grow. These new and big brains demanded much more energy and more concentrate, than they could get from vegetables. For the first time, we started eating more animals than vegetables.
And this was so for several thousand years, until about 10,000 years ago, agriculture appeared.
Appearance of agriculture
This change was drastic for our diet and had consequences on our way of life and also on our health and diets. The fossil record shows how when agriculture was introduced, our height, bone density, or average longevity were decreasing, why?
Of all the plant species there are, only a few were susceptible to being domesticated, and they are the ones that nowadays form the majority of our diet, wheat, corn, rice, soybeans, potatoes, etc ... But precisely these vegetable species, and the parts that we eat from them, are just the ones to the plant He is not interested in eating, his seeds or his reserve storage organs (potatoes). And that caused us and continues to cause us some problems.
The first humans who cultivated these species did not have to have a good time. It is very likely that they suffered enough poisonings or allergies, precisely because the seeds of almost all plants have chemical compounds designed to avoid being eaten (antinutrients). Wheat glute, even today, remains a problem for many people, and it certainly was at that time.
Over time, through thousands of crosses and trial and error, we were selecting the least harmful plant varieties and more productive, until we get the variety we have today.
In addition, access to mass consumption of vegetables has allowed, among other things, that right now, you are reading this post. Without the social specialization that allowed agriculture, the development of modern civilizations would have been impossible. But in return, many humans suffered and some continue to suffer some side effects.Teosinte, possible ancestor of modern corn
The graceful plant species, it came very well. Corn, for example, today is not found wild in the world. That is, it depends 100% on us as a species, or vice versa, it is not known. Your closest wild relative could be the teosinte, although it is not very clear. In short, we discovered some species that adapted very well to be cultivated, stored, and they achieved an unprecedented worldwide dispersion.
But what about the beneficial properties of vegetables?
Of course, I am not saying that you do not have to eat vegetables, but it is interesting to put them in evolutionary context to be able to know better their benefits and possible damages. Today it is not feasible, even if we wanted to, reproduce the diet we had thousands of years ago. In addition, domesticated vegetables have allowed us to have continuous access to a huge and varied source of vitamins, minerals and trace elements, which would otherwise be difficult to obtain.
In fact, at present, our animal consumption is very focused on lean meat, leaving aside parts that thousands of years ago we consumed very regularly, such as bone marrow and organs. I have the impression that we have been able to change these habits, thanks to more massive access to various vegetable sources. And this has allowed us a greater number of inhabitants on the planet and more complex civilizations.
That, of course, without counting the cultural and gastronomic factors that the use of vegetables has represented in the kitchen.
In short, giving up in our society the consumption of vegetables, even if some may have some harmful side effect, would deprive us in the practice of continuous access to essential sources of nutrients. But it does not hurt to keep in mind that what now seems more normal, has not been so for a long time in our evolutionary past, before the extension of agriculture.
The topic goes a long way and I don't want to get longer, I encourage you to expand it in the comments.