During Archean epoch (c. 3800 – 2500 mya) of Precambrian phase first prime unicellular organism appeared on the Earth that carried out the process of photosynthesis. (i.e. converting carbon dioxide in oxygen and organic matter) In this process these unicellular organisms developed skill of phagocytosis (Phagos, eating and Cyto, cell, in Greek) essential for their own survival. This skill of eating for survival developed by unicellular organisms has been retained by all living forms, plants and animals, of future. During Protezoic epoch (c. 2500 – 544 mya), green algae grew at the water edge and from that point of time, around 2, 95,000 plants have colonized most land habitats. In case of animals, according to colonial theory of animal origin, the ancestors of earliest animal were colonial protist, similar to modern choanoflagellida, which includes protozoan. During phanerozoic eon (c. 544 mya to the present) the unicellular became multi cellular.
Literature review of human diet reveals that from Paleocene up to early Holocene (c.65 mya- 10,000 years ago) hominid genus set omnivorous diet, obtained from hunting and gathering, comprising all nutritive requirements for healthy growth of the body, by adapting with environment. All ancestors of hominids were hunters and gatherers. They used to wander following seasonal migratory animals especially; herbivorous searching food and water by observing them man might have began gathering plants on the way, making them food gatherers and not food producers. In this process males used to do hunting while females used to collect variety of eating items such as leaves, fruits, tubers, seeds, nuts, berries along with insects, grubs, eggs, etc. This type of resource use developed habit in them to lightly exploit wide range of resources rather than intensively exploiting few. In this process they acquired detailed knowledge by judging multi-utility, possibility of acquisition and taming of animals and growing of plants and began domesticating them. But due to increasing urge of sedentism coupled with proper food supply in Mesolithic period (10000 – 7500 BC) when the population also increased, and by that time they might have realized that only plants and not animals can provide a desired, proper, timely and perennial food supply. As a result using the data base of plants they began agriculture in Neolithic period (7500 – 6500 BC). As an outcome during Holocene the domestication leading to agriculture was seen in different parts of the world, especially, on either side of equator between latitudes of 35° N and 35° S
Archaeological evidences form Indian subcontinent suggests that agriculture began to be practiced between the periods 7000 BC to 3000 BC, in and around Mehrgarh (Bolan and Indus valley). These first farmers cultivated barley, emmer, wheat along with ber, date, cotton etc. Thus, they tried to form balance of food comprising carbohydrates, proteins (from hunting) and minerals, etc. In the Indian subcontinent the generalized sequence of diffusion of agriculture based on archaeological evidence reveals that it began at dry point settlements such as Mehrgarh. With the passage of time, it went down to the Indus valley where on the base of agriculture, the Harappan or Indus Civilization thrived to the peak of prosperity (2600 BC - 1900 BC) in different spheres of life like cultural, socio- economic, along with agriculture. Study of pollen grains and sediments form Thar Desert, coastal Arabian Sea and Himalaya shows that by 2000 BC cycle of moist climate shifted to dry one and climate became drier by 1000 BC. Along with climate due to natural, anthropogenic and economic factors this civilization disintegrated (1900 BC – 1300 BC). During this period Aryans began to reach the Indus valley (1600 BC) and witnessed the whole process of disappearance of great civilization with shifting of people in search of favourable climate and other condition for living. Under such situation Aryans were also forced to move out and they began their journey in the east direction.
The nomadic pastorals, Aryans might have realized that for feeding herds and themselves agriculture is the only option and as a result slowly and gradually they learned the technique of tilling from natives. During this process the Aryans might have also realized that the basic requirements of perennial agriculture - fertile soil and ample water are available in abundance in the Ganges plains. In addition they might have recognized that, even though they were forced to clear forests to generate land for cultivation, the ecological balance can be maintained by protecting forests associated with Himalayas or Upper Ganges section and which can also provide required rains in monsoon as well as endow with necessary resources like medicine, wood, other forest products, etc. required for survival. Hence, they settled down in Ganges plains.
On their way to Ganges plains Aryans incorporated various ethnic groups with nonviolent interactions of cultural exchanges by learning and teaching various skills and techniques which laid the foundation of cultural progress inclusive of agriculture. For example, rice is not mentioned in the early Vedic literature. It is highly probable that the Aryans were not aware of rice in the beginning of their stay in the subcontinent and learnt its cultivation from the local communities when they reached the Ganges plains. Thereafter may be knowing the importance of rice in diet Aryans incorporated it even all religious rituals also. Aryans who came to India had variety of experiences and observations; they also had great memorizing capacity leading to certain conclusions and implementing them which got well documented in literature, Vedic and other specialized, covering various spheres of life. This is evident from Aryan Vedic literature which has no mention of cities as they had seen decline of Mohenjo daro and Harappa and first reference of cities like Vaishali (Bihar), Kapilavastu (Nepal) comes in Buddhist literature (600 BC) that is after 1000 years of their stay in Indian subcontinent. But they slowly and gradually mastered the art of agriculture which is corner stone of the culture which emerged in India and reflected in literature also.