The genetic history of North Africa has been heavily influenced by geography. The Sahara desert to the south and the Mediterranean Sea to the North were important barriers to gene flow from sub-Saharan Africa and Europe in prehistoric times. However, North Africa is connected to Western Asia via the Isthmus of Suez and the Sinai peninsula, while at the Straits of Gibraltar North Africa and Europe are separated by only 15 km (9 mi), similarly Malta, Sicily and Crete are close to the coasts of North Africa.