One of the world’s most important seed banks has left Syria, and it won’t be returning. Aleppo, Syria, has as good a claim as any to the title of “world’s oldest city.” It is certainly among the longest to be continuously inhabited. There are hints that nomads camped out just north of Aleppo, as early as 11,000 B.C. People used to say that Abraham had climbed its highest hill, to survey the surrounding landscape. Alexander…