By analyzing stalagmites in a cave in northern Oman, a team of scientists have found evidence of a severe draught that struck the southern part of the Arabian Peninsula in the beginning of the 6th century CE. Reading the data they collected in the context of the historical record, they concluded that lack of rainfall contributed to the demise of the Jewish kingdom of Himyar that once dominated the region, thus creating a geopolitical vacuum that facilitated the rise of Islam. Ariel David writes:
The Himyarite kingdom was founded in the late 2nd century BCE in today’s Yemen. It gradually extended its control over most of southern Arabia by conquering neighboring states, including Saba (or Sheba), the ancient kingdom whose queen of biblical fame supposedly visited King Solomon. During the 4th century CE, the Himyarite elite abandoned its ancestral polytheistic beliefs and converted to Judaism, followed by an unknown percentage of the broader population.
The choice of Judaism as a state religion may have been a way to maintain neutrality among various rival regional powers: the Christians of the Byzantine empire and of the kingdom of Aksum in Ethiopia, as well as the Zoroastrians of the Persian empire. All these powers eyed the lucrative spice trade of Arabia that enriched Himyar and they eventually played a part in the kingdom’s demise.
Until the 6th century, Himyar managed to fend off foreign encroachment, but around 525 it suddenly fell to an invading Ethiopian force. . . . With Himyar definitely out of the geopolitical picture, the Byzantine and Persian empires were now free to vie for influence over southern Arabia and its rich trade in myrrh and frankincense. But very quickly these two powers would also cripple each other in a long and bloody conflict that lasted from 602 to 628.
With the economic turmoil and political fragmentation of the period it was only a matter of time until the tribes of Arabia united under a new leadership, which they ultimately found in the prophet Mohammad and his successors from the 620s onward.