An analysis of ancient fish bones from 30 archaeological sites in Israel and Sinai which date from the Late Bronze Age (1550-1130 BC) until the end of the Byzantine period (640 AD) finds that Judeans commonly ate non-kosher - lacking scales or fins - fish.

This finding sheds new light on the origin of Old Testament dietary laws that are still observed by many Jews today - and how well people adhered. Some things become part of culture because they are common. If people in Tennessee banned eating sharks it wouldn't be a huge loss. The ban on finless and scaleless fish deviated from longstanding Judean dietary habits, the authors note.

The Old Testament was penned at different times, beginning in the centuries before the destruction of Jerusalem in 586 BC and into Hellenistic times (332-63 BC). A set of passages repeated twice forbids the eating of certain species of fish.

The Book of Leviticus states: "Everything in the waters that does not have fins and scales is detestable to you", and Deuteronomy decrees that '...whatever does not have fins and scales you shall not eat; it is unclean for you.'

In both, the references immediately follow a prohibition on 'unclean' pig which has received wide scholarly attention. However, the origins and early history of the seafood ban have not been explored in detail. 

The authors in this study set out to discover when and how the fish prohibition first arose, and if it was predated by an earlier taboo practiced prior to the editing of the Old Testament passages. They also sought to establish the extent to which the rule was obeyed.

Co-author Omri Lernau from Haifa University analysed thousands of fish remains from dozens of sites in the southern Levant. At many Judean sites dating to the Iron Age (1130-586 BC), including at the Judean capital city of Jerusalem, bone assemblages included significant proportions of non-kosher fish remains. Another key discovery was evidence of non-kosher fish consumption in Jerusalem during the Persian era (539-332 BC). 

Non-kosher fish bones were mostly absent from Judean settlements dating to the Roman era and later. The authors note that sporadic non-kosher fish remains from this later time may indicate 'some degree of non-observance among Judeans'.

The authors now intend to analyze more fish from around this timeframe to establish when Judeans began to avoid eating scaleless fish and how strictly the prohibition was kept.