एतदन्तर्जालस्थलमहं संस्कृतभाषामर्पयामि।

   Information on various theories about the origin & evolution of the Sanskrit language (संस्कृतभाषा) & its scripts, and ancient literature, is given briefly but concisely.

The Sanskrit language (संस्कृतभाषा) is believed to have evolved around 3200 BCE in the northern part of the Subcontinent; probably in the Indus Valley.
It is currently used mostly in India and some parts of South Asia.

Most theories state that the Aryan Race is the originator of संस्कृतभाषा, and that it was their primary language.

The other theories which suggest that Sanskrit was primarily influenced by other Non-Aryan languages have a major flaw in them. As per such theories, Sanskrit was modified into the abugida (alphasyllabary), and adopted in the subcontinent in a span of time as short as 100 years ! Anyone who has considerable knowledge of Sanskrit would know about its complexities. It is quite far fetched to consider it to be derived even in a span thrice as long. Hence we will go with the "Aryan Origins" theory.

From the history of Aryans, we can infer that a complex culture would take quite a long time to develop.

Hence, even if संस्कृतभाषा (Sanskrit) took a thousand years to evolve (which is easily possible considering its complexity), it would still be 6000 years old. So the Aryans are considered as non-nomads. The occurrence of Sanskrit in the Subcontinent coincides with the arrival of the Aryans. This has led to the conclusion that the Aryans brought Sanskrit with them.

Even though a few obscure theories state otherwise, they are mostly ignored.

After the Aryans settled in the subcontinent and the interracial wars ended, cultural development became prominent. Sanskrit developed into a modified form around 600 CE. Since then, there haven't been any significant changes. The current form was adopted around 1500 CE.