I found this wonderful synopsis from one of my favorite cookery blogs, by Rinku Bhattacharya.
Indian Cooking derives from a 4000 year old timeline, during which culture has changed, geographical boundaries have changed significantly leading to confusing terms such as sub-continental cuisine while other parts of a region want a separate culinary identity. Unfortunately since India's root cuisine precedes the subsequent subdivisions trying to distinguish between modern India's cuisine and that of its neighbors, is not really feasible.
Indian Cooking has however evolved significantly over time and the varying influences brought into the country by the various rulers and travelers, it has not lost its original identity, rather become richer with the assimilation of the myriad influences. This is very apparent in some of the unique regional cuisines, which we will discuss later. The following historical timeline is from a culinary perspective rather than a complete historical guide.
2000 BC and earlier: Most people believe that the origins of Indian history and therefore the cuisine are as old as mankind itself. The earlier formal civilization is the Mohenjedaro and Harrapan Civilization, which is at about 2000 BC. Most people believe that the Ayurvedic tradition of cooking which is a complete holistic approach to cooking, evolved at this point in time. This lays the foundation of the concept that everything we eat affects both our body and mind, therefore food should be pure, from nature, and balanced. The core balance consists of balancing the six tastes Sweet. Sour, Salty, Pungent, Bitter, and Astringent. These tastes relate to the attributes of Essence and Effect.
1000 BC: At this point we see the first movement of outsiders into the country, this forms the origins of the Indus Valley Civilizations. The Mohenjodaro people are believed to have been pushed to the Southern Part of the country and the cuisine there is still largely vegetarian. The roots of Hinduism are shaped at this point, the Vedas or the religious texts are developed at this point as is the Mahabharatha. The caste system is developed at this point in time, dividing food habits of people broadly by caste, for example the Brahmins for the most part were vegetarians while the Khatriyas were non-vegetarian.
600 BC: We see the emergence of Buddhism and Jainism, the later has a marked influence on the cuisine in some parts of the countries. Jains were strong believers in non-violence, traditional Jain cuisine apart from being cooked without meat was also cooked without onion and garlic.
400 BC: Parts of India were ruled by Alexander the Great, in the 326 BC period, but generally this period was the period of the Mauryan Dynasty. The Mauryan dynasty especially King Ashok was responsible for the further development of Buddhism, this period also saw the development of Buddhism outside India, which would lead people to people there must have been some cross-pollination with food. There are references to the development and production of several varieties of natural liquor that were consumed for recreation. The Mauryan economy was also agriculture driven which resulted in the base of all the grain cuisine in India.
AD 1200: This period was the period of several North Indian dynasties, including the Gupta Dynasty which was noted for its love of the arts and there were several visiting travelers during this time. This was also known as the Golden Age of India Art, there were several travelers who visited India and carried with them knowledge and products like tea and spices. In the South of India notable dynasties were the Hoysala Dynasty. But from a culinary perspective there are still no significant external influences brought into the country.
1200-1500AD: This period is the period of Muslim Invasions and the first entry of several foreign invaders into the country. Vasco Da Gama arrived in India in 1948 to explore opportunities for trade which later resulted in colonization of parts of India by the Portuguese, the most notable example of this influence is seen in the cuisine of Goa, in Western India. The Khilji Dynasty ruled in Northern India during a significant period of time, an interesting travelogue of this period is provided by Ibn Batuta a Moroccan traveler in the court of Mohamed Bin Tughluk. In one instance he describes a meal served to him where is outlines the use of ghee, yogurt, pickles, and that it comprised of several courses including a milk-based dessert.
1500-1800 AD: This is the period of the Moghul empire and the emergence of the Moglai cuisine that people now associate with India. It includes the addition of several seasonings like saffron, the addition of nuts and cooking in the "Dum" or sealed pot method of cooking. In the South of India, you have the Sultan dynasty in Hyderabad where the similar influences are permeated into the region. There is a continuation of other European influences in parts of South India such as Kerala where you see the beginning of the Syrian Christian cuisine.
1800 1947 AD: This was the period of the British rule in India and the love affair of the English with Indian food. This generally was hardly a glorified period in Indian history, but the British loved the general elaborate way of eating and adapted several of the food choices to their taste and developed the "curry" as a simple spice to help them cook Indian spice. This period resulted in the emergence of the Anglo-Indian cuisine and the emergence of certain "Raj" traditions like that of "high-tea" an elaborate late afternoon meal served with tea.
1947 AD: This is the post-independence period which changed Indian cuisine to sub-continental cuisine since the Indian land mass was divided into several countries most notably Pakistan and Bangladesh, that inherited the following ancient history that has developed into today's culinary tradition.