Endogamy fails when the ratio of males to females in a group is not 1:1, a simple mathematical fact. Many castes have disappeared, many emerged. Genetical evidence just show that people prefer to marry within that particular sub-caste, but it is not a constituent property of caste--let alone a system of castes. If we apply this logic (endogamy meausurement), castes existed in other continents, countries far away from India. In that case, we see a phenomenon not unique to India.

BTW, I am not denying that practices exist, practices are continued, even modified. Nor am I denying that jaatis-exist. I am not even denying that there are fights between different jaatis at different places. There is a difference between phenomena and explanations(descriptions). Over the time, theory-laden descriptions of phenomena start replacing the very phenomena. That facts are theory-laden or that facts are facts of a theory--is not some rhetoric.

Once caste-system (sociopolitical system, as you put), a theoretical entity, is postulated to explain various phenomena, now all these phenomena are re-described using this language. When I deny these re-descriptions, you seem to think that I am denying phenomena (for example, people prefer intra-jaati marriages), as you call this denial of re-descriptions as rhetoric.

Practices exist, jaatis exist, various phenomena exist, does the caste-system exist?