Although the Arabian Peninsula is covered in deserts and mountains, such as the Asir Mountains, it has been the birthplace of multiple civilizations. With the use of key geographic features, various groups of people have been able to thrive and prevail. The Tigris and Euphrates rivers provided civilizations with a source of water and fertile land that allowed for sustenance and an agriculture-based economy. Deserts, like the Syrian one, protected the population from invasions and promoted the economy with the use of camel caravans. Additionally, the Red Sea encouraged extensive trade with foreign nations that led to the development of intellectual and prosperous empires, such as the Kingdom of Sheba. The Mediterranean Sea allowed contact and cultural diffusion between Arabs and Europeans. The first humans to settle the Arabian Peninsula adopted foraging to survive around 15-20 thousand years ago. Fifteen thousand years ago, the last ice sheet melted and the geography of the peninsula changed dramatically (“History”). The climate was remodeled from savannah to dry and arid desert (“History”). Approximately 75% of the Arabian Peninsula is covered by deserts such as the Arabian Desert, the Syrian Desert, and the Rub al-Khali Desert (“The Islam Project”). Due to climate change, nomadic tribes have dispersed across nutrient-rich lands in the Fertile Crescent and along the peninsula's edge. The Fertile Crescent lies between the Tigris and Euphrates rivers and provided an excellent source of water during the Neolithic Revolution, when nomads settled and discovered agriculture (“The Islam Project”). However, the Tigris and Euphrates rivers run parallel to each other and are notorious for their unpredictable floods, causing devastation among settlements... middle of paper... in East and North Africa. Cambridge: Cambridge UP, 1988. Print."Mediterranean Sea." Britannica School.Encyclopædia Britannica, Inc., 2014. Web. 18 March 2014. .Penn, James R. Rivers of the World. Santa Barbara, CA: ABC Clio, 2001. Print."Red Sea." British School. Encyclopædia Britannica, Inc., 2014. Web. March 18, 2014. “Sabaʾ.” British School. Encyclopædia Britannica, Inc., 2014. Web. 18 March 2014. “Tigris-Euphrates River System.” Britannica School.Encyclopædia Britannica, Inc., 2014. Web. 30 April 2014. “Umayyad Dynasty.” Britannica School.Encyclopædia Britannica, Inc., 2014. Web. March 18. 2014. .