When one reads the Ancient Indian History and Ancient History as a whole, the much-discussed theory of Indo-European migration to India often comes up.
Ancient Indian History in introductory books is traced beginning from the early stages of ancient humans of the Paleolithic period who were food gatherers and hunters and then moving onto the Mesolithic and Neolithic periods where humans become food producers. As a result of this, we find settlements in the form of villages and a much more settled and social life where people engage in things for leisure as opposed to just striving for survival. They indulge in trade and in making ornaments, pots etc.
We then come across the rich history of the Indus- Valley (Harappan) civilization and its sudden (a little mysterious) demise.
As far as I am aware there is no evidence that supports that there were major linguistic advancements (in the form of poetries etc) in the Indus-Calley civilization even when there were major advancements in other areas like megalith structures, roads, drainage systems, etc.
At the fall of the Indus Valley Civilization, we come across the Aryan (Indo-European) Migration Theory which discusses how the people who had horses and knowledge of Indo-European (Vedic) languages migrated to India and displaced the Indigenous population. They then created the Vedas because of which the period after this displacement is called Vedic.
Nothing particular is told about the origins of these Aryans.
From were did the Aryans originate?
Were Aryans part of the first human civilization and were they related to Sumers?
These are a lot of questions that come up as there seems to be a jump in the chronological evolution of ancient history (at least in what I've read). The books simply put this theory without tracing its origins which makes the Aryans seem some mysterious alien species that came from somewhere around places like Germany, Iran, etc with a lot of knowledge and horses and settled. I am interested in knowing more about these Indo-European people and their history traced to when they were food gatherers.