A profession becomes a jāti when the people who share the work also begin to share marriages — at that point the group stops being something you join and becomes something you are born into. The Kāyastha example in the box shows the steps.
Why marriage is the decisive step: as long as outsiders can enter, a group is an occupation. Once people mostly marry inside it, the children are born inside it, and within two or three generations membership is settled at birth. That is what turns a profession into a jāti — and it is why the chapter builds its whole description of jātis around marriage: “this created communities in which most people married within their group.”
Tip — the chapter’s warning: “Such a process was complex and could vary from region to region.” The Bengal story is one example, not a rule for all of India. The chapter also reminds us that “much of the data on the jātis comes from texts, and some from inscriptions, but overall there are many gaps and unanswered questions”, and that varṇa and jāti were “flexible rather than rigid” — the Pālas and Kākatīyas moved from being regarded as Śhūdras to being regarded as Kṣhatriyas.
A profession becomes a jāti when the people who share the work also begin to share marriages — at that point the group stops being something you join and becomes something you are born into. The Kāyastha example in the box shows the steps.