On the rise of Islam, two main theses prevail. On the one hand, there is the traditional view, as espoused by most historians prior to the second half of the twentieth century and by Muslim scholars. This view, the so-called "out of Arabia"-thesis, holds that Islam as a phenomenon was a new, alien element in the late antique world. Related to this is the Pirenne Thesis, according to which the Arab invasions marked—through conquest and the disruption of Mediterranean trade routes—the cataclysmic end of Late Antiquity and the beginning of the Middle Ages.