If everyone ate only fruits the world would transform into a real paradise with all the fruit trees which would clean the air we breathe. There are 7 billion humans on the earth. Just imagine the impact they would have on the earth if they ate only fruits and nuts coming from the trees which clean the air. In Turkey where I live at this time there is high amounts of olive and olive oil consumption. So there are forests of olive groves starting from Northern part of the Aegean and continuing all along the coast down to the Mediterranean. An olive tree lives about 600 years and once it is planted it will keep giving olives every year and clean the air for as long as it lives. They will also provide shelter for wildlife.
Fruits are essential for healthy life. It is because this was the first food for those monkey looking humans who appeared in the world about 4 million years ago in a very suitable tropical climate in Africa. They had plenty of delicious fruits and nuts there. They used their bare hands to collect and eat those fruits and they opened nuts with shells with their bare hands. At those times they ate only fruits and nuts and some plants. They did not eat meat at those times. They sometimes fought with animals and they killed them using a stone or a club. They certainly tasted the blood of the dead animal but it was disgusting to them. So it is thought they kept this diet for about 2.300.000 years until they were in colder climates and invented the fire. Then they started to cook the animals they killed and ate them. So the vegetarian digestion system of the humans was slightly modified into a system which could eat and digest meat as well. The canine teeth was developed. However it is only visible at some people and doesn’t exist at many others. The digestion system of humans is still basically vegetarian. Our hands, the structure of the teeth, enzymes in the mouth and stomach, length of the bows are all showing humans to be basically vegetarians. Human bodies are not designed to kill an animal with their bare hands unless they have a stone or a club. But our hands, fingers and nails are made to collect all sort of fruits and they are designed to open nut shells by means of the nails.