Necessary, because if it were not true — if the origin of a food prohibition does NOT need to be explained with reference to the understanding of the people who adopted and enforced the prohibition — then we have no reason to think that the ancient people’s lack of access to the recent data shows that the recent data can’t explain the origin of the food prohibitions. Why would the ancient people’s access to the data make any difference if their understanding doesn’t matter? We could simply analyze the recent data and come up with theories about the origin of the prohibition, regardless of whatever the ancient people knew or didn’t know. The author must assume we can’t do this in order for her premise to support the conclusion.

Not necessary, because even if the problems of society might lead to contradictory food prohibitions, all the author is trying to prove is that the recent data can’t explain the origin of the prohibitions. Whether the prohibitions are contradictory or not has no bearing on whether we can explain how those prohibitions came about.

Not necessary, because even if the social importance of the origin IS dependent on the nutritional value, all the author is arguing is that the recent data can’t explain the origin of the prohibitions. Whether nutritional value is related to the origin has no connection to the importance of the recent data and whether it can reveal the origin of the prohibitions.

Not necessary, because even if the original purpose of a prohibition is NOT forgotten after a few generations — in other words, if people continue to remember the original purpose many generations later — that has nothing to do with whether the recent data can explain the origin of the prohibitions. What matters is whether we can look at the data and determine why the prohibitions first came about; what people remember about the original purpose of the prohibitions doesn’t affect our interpretation of the recent data, and it doesn’t relate to ancient people’s access or lack of access to that data.

Not necessary, because even though the ancient people didn’t have access to the recent data that modern researchers have, that doesn’t imply a “nontechnical understanding” of the medical functions of the prohibitions. Maybe the ancient peoples did have a technical understanding based on a different set of data that they collected.