Short answers, pulled from the story.
Genetic and fossil evidence indicates that anatomically modern humans evolved in the Horn of Africa around 200,000 years ago. Homo sapiens idaltu and Omo Kibish are considered the immediate ancestors of all living humans. A 2019 study using 260 CT scans placed the emergence of modern humans between 350,000 and 260,000 years ago through a merging of South and East African populations.
The Swahili Coast refers to the coastal seaboard of Tanzania, particularly Zanzibar, and Kenya, where Bantu-speaking peoples mixed with Muslim Arab and Persian traders over many centuries. The Swahili language that resulted carries heavy Arabic loan-words in its vocabulary but retains purely Bantu grammar and structure. It is now spoken by at least 80 million people as a first or second language and holds official status in Tanzania, Kenya, and Uganda.
Vasco da Gama visited Mombasa in 1498, making the Portuguese the first Europeans to reach the East African coast by sea. Portuguese presence officially began after 1505, when Don Francisco de Almeida conquered Kilwa, an island in present-day southern Tanzania. Fort Jesus was built in Mombasa in 1593 to consolidate Portuguese control, though British, Dutch, and Omani Arab pressure eroded that influence during the 17th century.
United Nations estimates from 2017 project the population of Eastern Africa will reach 890 million by 2050, up from 260 million in 2000. By 2100 that number is projected to reach 1.6 billion. The 2017 CIA estimate already placed the regional population at 537.9 million.
East Africa receives less rainfall than expected for its latitude due to two main factors. The Somali Jet, a fast wind system, brings cool southern hemisphere air across the region during the northern summer. East-to-west river valleys in the East African Rift channel moisture-laden Indian Ocean winds toward the Congo Basin rather than over East Africa. On the northern Somali coast, annual rainfall can be less than 100 millimeters.
The East African Rift, formed by the separation of the Somali Plate and the Nubian Plate at 7 millimeters per year, defines much of the region's terrain. It created Mount Kilimanjaro and Mount Kenya, the two tallest peaks in Africa, as well as Lake Victoria, the world's second-largest freshwater lake, and Lake Tanganyika, the world's second-deepest lake.