Middle Stone Age
The Middle Stone Age (or MSA) was a period of African prehistory between the Early Stone Age and the Later Stone Age. It is generally considered to have begun around 280,000 years ago and ended around 50–25,000 years ago. The beginnings of particular MSA stone tools have their origins as far back as 550–500,000 years ago and as such some researchers consider this to be the beginnings of the MSA. The MSA is often mistakenly understood to be synonymous with the Middle Paleolithic of Europe, especially due to their roughly contemporaneous time span, however, the Middle Paleolithic of Europe represents an entirely different hominin population, "Homo neanderthalensis", than the MSA of Africa, which did not have Neanderthal populations. Additionally, current archaeological research in Africa has yielded much evidence to suggest that modern human behavior and cognition was beginning to develop much earlier in Africa during the MSA than it was in Europe during the Middle Paleolithic. The MSA is associated with both anatomically modern humans ("Homo sapiens") as well as archaic "Homo sapiens", sometimes referred to as "Homo helmei". Early physical evidence comes from the Gademotta Formation in Ethiopia, the Kapthurin Formation in Kenya and Kathu Pan in South Africa.
Middle Stone Age
In a different convention, MSA refers to sites characterized by the use of Levallois methods for flake production, to the exclusion of Acheulean sites with large cleavers or handaxes.
Following McBrearty and Tryon (2006), the term "early MSA" (EMSA) refers to sites predating the 126 kya interglacial, and 
"later MSA" (LMSA) refers to site younger than 126 kya.
In this convention, Fauresmith sites of 500 to 300 kya are within the ESA, and the MSA begins after about 280 kya and is largely associated with "H. sapiens", the earliest reliably dated MSA site in East Africa being Gademotta in Ethiopia, 
at 276 kya. 
The Middle Awash valley of Ethiopia and the Central Rift Valley of Kenya constituted a major center for behavioural innovation. It is likely that the large terrestrial mammal biomass of these regions supported substantial human populations with subsistence and manufacturing patterns similar to those of ethnographically known foragers.