The people are the earliest known inhabitants of africa's mediterranean coast

The Berbers are the earliest known inhabitants of Africa's Mediterranean coast. They are an ethnic group indigenous to North Africa. They lived in an area stretching from the Mediterranean Sea to the Niger River, and from the Atlantic Ocean to the Siwa Oasis in Egypt. Today they live in scattered communities across Morocco, Egypt, Tunisia, and Libya, for example. Today, Berbers are identified primarily by the language they speak as well as their distinctive traditional customs such as music and dance types. 

The answer is monsoons.