Supporting the Origin of Modern Humans from Africa

Solomon Egwuonwu        

ANTH 101

11329571

Supporting the Origin of Modern Humans from Africa

Where do modern humans come from? How did they populate the Earth?  What type of evidence do anthropologists use to support their theories? For decades researchers have been deeply interested in these questions. The topic of modern human origins has a long tradition in anthropology. The observed variation in human species puzzled early scholars, and the journey to answer these questions has been a central element in the discipline. In this paper I intend to show how evidence supports out of Africa hypothesis for the origin of modern Homo sapiens.

It is widely accepted that modern humans originated in Africa. Fossil evidence shows that the early homo species evolved in Africa and migrated to Europe and Asia (Wood and Collard 1999). The first migration occurred about 1.9 million years ago. At that time, the species known as Homo erectus dispersed from Africa, and eventually colonized the European and Asiatic continents. Homo erectus proved to be a successful species, and demonstrated that widespread migration was possible without the complex behavior we see in modern humans. These species lived from 1.9 million years ago to around 143,000 years ago (Anton 2003). Current data suggest that modern humans evolved from archaic humans primarily in East Africa.  A 195,000 year old fossil from the Omo 1 site in Ethiopia shows the beginnings of the skull changes that was associate with modern people, including a rounded skull case and possibly a projecting chin.  A 160,000 year old skull from the Herto site in the Middle Awash area of Ethiopia also seems to be at the early stages of this transition.  It had the rounded skull case but retained the large brow ridges of archaic humans.  Somewhat more advanced transitional forms have been found at Laetoli in Tanzania dating to about 120,000 years ago.  By 115,000 years ago, early modern humans had expanded their range to South Africa and into Southwest Asia (Israel) shortly after 100,000 years ago.  There is no reliable evidence of modern humans elsewhere in the Old World until 60,000-40,000 years ago, during a short temperate period in the midst of the last ice age (Aiello 1993).

The major evidence the African origin models has come from several entirely different fieldss. Undoubtedly it has come from the recent genetic evidence, but it also has come from the radical advances of the past two decades in absolute dating of the Middle and Late Pleistocene archeological sequence of sub-Saharan Africa. The African archeological sequence has traditionally been divided into three stages, namely the Early Stone Age which includes both the Oldowan and Acheulean industries, the Middle Stone Age which is typologically equivalent to the European Mousterian industry, and the Late Stone Age which, like the European Upper Paleolithic, shows many advances over the earlier industries. Under this system the obvious conclusion was that Africa was a technological backwater. The Middle Stone Age largely postdated its typological equivalent, the European Mousterian, and the Late Stone Age did not appear until well after the European Upper Paleolithic had disappeared. Robust-appearing hominid fossils such as Kabwe (Zambia) were also believed to be contemporaneous with more advanced hominids in Europe, supporting a hypothesis of evolutionary retardation in Africa (Aiello 1993).

A second migration occurred around 125,000 years ago. This time, Homo sapiens moved out of the African continent. Homo sapiens expanded to regions previously occupied by earlier Homo species. At one point during the Middle Pleistocene, there were at least three different Homo species which are Homo ergaster/erectus in East Asia, Homo neandertalensis in Europe, and Homo sapiens in Africa (Relethford 1999). Thus, the relationship between the diverse Homo species was difficult to measure.

Recent genetics have proved to be useful in approaching this problem.  The debate about the relationship between Homo sapiens and other Homo species during the time of the out of Africa expansion was about whether they did interbreed or not, and the degree of this hypothetical interbreeding. Two theories emerge from this line with divergent point of view which are the Recent African origin and the Multiregional origin.  The Recent African origin theory holds that the early Homo species in Eurasia (Europe and Asia) evolved independently from the African populations with no interbreeding and cultural exchange between them. In this point of view, I think modern humans derive from the evolution of the Homo lineage in Africa that subsequently migrated to Eurasia around 125,000 years ago replacing the Homo erectus populations (Stringer and Andrews 1988). On the other hand, the multiregional theory supports the idea that the origins of modern humans can be traced back to the initial Homo erectus expansion. This theory suggests that African and non-African populations did in fact interbreed and that allowed evolution through species and with changes as well as local adaptations that led to differentiation (Wolpoff et al. 2000). From these two theories, the main point is to clarify the evolutionary history of human species, and provide the foundations of what we define as modern human.

Back in the day, theories of human origins have been based on fossils record. Nowadays, with the advances in and applications of genetics in anthropology, it is possible to address the problem with a new approach. We can now test the hypothesis about interbreeding and the core evolution of Homo species. For the past two decades, paleoanthropologists have taken advantages of genetics to solve this and other questions. There are many definitions of genetics depending on the angle scholars are looking at. There’s this definition that caught my attention, genetic as the study of heredity and variations. The study of genetics covers many topics in biology and particularly in evolution. The study of genetics is essential for scholars because it provides a route to answer questions about the evolution of life on Earth. The focus of genetics is the gene, which is nothing but a long stretch of DNA codes for a protein or an RNA product (Robert et al. 2007). Genetic studies through DNA analysis enables anthropologist to test the ideas about the origin of modern humans from Africa by examining ancient and modern populations.

Scholars have often argued that modern human DNA has a common ancestry in Africa between 140,000 years and 290,000 years ago, that the ancestral stock of modern Eurasians diverge from the African stock between 90,000 years and 180,000 years ago, and that interbreeding between these modern people and indigenous Eurasian archaic hominids was, at most, minimal. In a more recent assessment of the implications of their DNA data on Late Pleistocene human population history, the rather staggering implication is that the dispersing African population of modern humans replaced the non-African resident populations without any interbreeding (Fred 1989).