What is Aryan theory?

The Aryan theory, propounded by Max Mueller in the 19th century and linguist William Jones, states that Aryans were a class of fair-skinned, agrarian noblemen who came from Central Asia to inhabit India after the Indus Valley period. They destroyed the Indus Valley civilization and settled in India, and also composed the Vedas. However, this theory, also called the Aryan Invasion Theory, has been refuted. Modern archaeologists say Aryans were indigenous people who resided mainly along the Saraswati river. Once it dried up, they migrated to regions within and outside India, and also settled in the Indus Valley.