The pork ban may have hemmed in Islamic expansion geographically

Evidence

Some historians have even argued that the ban on pork set the limits of Islamic expansion. The Islamic religion came out of Arabia in the seventh century, spread very rapidly eastward and westward and northward and southward, and then came to a stop in Spain, the Balkans, and China, three regions depending very heavily on pig husbandry. — Bernard Lewis, From Babel to Dragomans, 244

Categorization

• QUESTION: Is this a real scholarly thesis with a named source, or is the author being speculative? Worth chasing the actual argument.