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.
Three-age system
Sir John Lubbock's use of the terms Palaeolithic ("Old Stone Age") and Neolithic ("New Stone Age") were immediately popular. They were applied, however, in two different senses: geologic and anthropologic. In 1867-1868 Ernst Haeckel in 20 public lectures in Jena, entitled "General Morphology", to be published in 1870, referred to the Archaeolithic, the Palaeolithic, the Mesolithic and the Caenolithic as periods in geologic history. He could only have got these terms from Hodder Westropp, who took Palaeolithic from Lubbock, invented Mesolithic ("Middle Stone Age") and Caenolithic instead of Lubbock's Neolithic. None of these terms appear anywhere, including the writings of Haeckel, before 1865. Haeckel's use was innovative.