Anu was the second son sired by King Yayāti (Yayati) to Śarmiṣṭha (Sarmishtha).
When Yayāti, cursed of acquiring untimely senility by Śukrācārya (Sukracharya), requested each of his sons to exchange his youth with the king’s old age, Anu directly refused this plea of his father. He said that old men, like infants and lowly people, eat whenever they please; nor can they perform sacrificial Vedic rites with the holy fire – therefore he would not take up his father’s old age. This enraged Yayāti, who cursed his son that he would face exactly the same fate as he himself uttered – he also would not be able to perform the sacrificial Vedic rituals with the holy fire.
Vaiśampāyana (Vaisampayana), the impartial narrator of Mahābhārata (Mahabharata) remarks that since then mleccha (mlechchha; ethnic groups having foreign, non-Vedic culture and clashing values and interests) tribes originated from Anu’s line – anostū mlecchajātayaḥ.
Later research shows the point of origin of the concept of mleccha tribes stemming from Anu’s line to be a massive result of interclass and interracial mixing in lineage. Ṛgveda (Rigveda) depicts Anu as a typical Indra-and-Agni-worshipping Aryan
According to Purāṇas (Purana), Anu sired three sons, namely Sabhānara (Sabhanara), Cakṣu (Chakshu) or Cākṣusa (Chakshusha) and Parekṣu (Parekshu) or Paramekṣu (Paramekshu).