From the most ancient times the Hindus have believed that mind is a product of the food we take, even as the body is, and that purity of food is conducive to the purity of mind (vide Chāndogya Upaniṣad 7.26.2). As a corollary of the doctrine it was also believed that food handled by persons of doubtful integrity could be defiled and the same had to be purified by appropriate rites. The doctrine seems to have been further extended to declare that certain classes of people, if they were allowed to sit in the same paṅkti (row of people sitting for food), could defile the whole row and hence were branded as ‘apāṅkteya’ or unworthy of being allowed to sit in the row along with others. Sometimes they were also called ‘paṅktidūṣakas,’ those who defile the row.
Though the dharmaśāstras have given long lists of persons who are apāṅkteya, the lists vary from book to book. Manusmṛti (3.150-166) by far gives the longest list, of 93 persons.
A perusal of these lists shows that persons who have given up their allotted duties (varṇadharmas) and have taken to other means of livelihood, perpetrators of heinous crimes, patients suffering from incurable or infectious diseases, those addicted to drinks and debauchery as also the others who do not follow even elementary principles of ethics and etiquette have all been stigmatized as apāṅkteyas.