New Findings Change the Theories of Human Origins
The evolution and spread of Homo sapiens is perhaps one of the greatest mysteries in all of science. Until recently, it was believed that the origins of the species and the ancestors of every person now alive originated in one specific part of Africa.
This theory was for a long-time the accepted wisdom, but it has been challenged in recent years. Now it is increasingly probable that H. sapiens originated in several separate areas of Africa.
Human Origins and a Garden of Eden
It was once held that H. sapiens first emerged in Eastern Africa and flourished in some Stone Age ‘Eden’. They lived in a grassland area where game was plentiful or near an estuary rich in fish. This, it was believed, was the cradle of humanity and where we acquired our distinct physical features and cognitive skills.
These modern humans first conquered the continent and later spread all over the world. This was based on the pioneering work of Allan Wilson of the University of Berkeley, California.
Wilson and his colleagues studied mitochondrial DNA and they established that humans originated in one area, namely Eastern Africa. Wilson even went so far as to state that there was a single mother of humanity - an African Eve. However, more recently, several experts have suggested Southern Africa, possibly Botswana was the cradle of humanity.
Through random drift or selection, the female-lineage traces back to a single female, known as Mitochondrial Eve. In this example of human origins over five generations colors represent extinct matrilineal lines and black the matrilineal line descended from mtDNA MRCA. (ChrisTi / CC BY-SA 3.0)
No Single-Origin of Humans
However, theories as to one single location for the origin of H. sapiens have been undermined in recent years and many reject them as too simplistic. According to The Guardian, analysis of the Y-chromosomes (which determines masculinity) “suggest that modern humanity probably originated in West Africa”. In short, if this analysis is accepted alongside the Wilson theory, H. sapiens males originated at the opposite end of the African continent from where females first emerged, so how could they mate?
Also, some of the oldest early human fossils found have been unearthed in North Africa, a different area of the continent than would be expected. Moreover, certain anatomical features such as a rounded skull was found in Ethiopia, while the first evidence of symbolic thought, namely rock-art was found in Southern Africa.
A rounded skull fossil was found in Ethiopia, one of the locations of human origins. (Ryan Somma / CC BY-SA 2.0)
This is more evidence that the behavior and characteristics of modern humans evolved in different parts of Africa. Chris Stringer, of the Natural History Museum, London, is quoted by The Guardian as saying that “the immediate predecessors of modern humans probably arose in Africa about 500,000 years ago and evolved into separate populations”.
This is characteristic of many animal species. It is possible that during arid periods when the deserts expanded groups of H. sapiens became separated. They evolved separately and developed different social and cultural skills and even different physical features.
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Map of the fossil sites and locations of some of the sites of human origins. (Kameraad Pjotr & Sting / CC BY-SA 3.0)
Complex Origin and Human Evolution
When the climate was more benign the different groups would reconnect and they mixed their genes. They also shared ideas and cultural practices. Science Alert reports that “ H. sapiens evolved all over Africa in interlinked groups and became more similar over time”.
It appears that populations became separated and reconnected many times over 400,000 years, because of climate change and environmental factors. The Guardian reports that “the end product was H. sapiens, the species that is more or less the version of modern humanity”.
As a result, there was in all likelihood no single ‘Eden’ or cradle of humanity. Rather the development of modern humans was a result of a complex set of interactions. However, while there is no one place that can be claimed to be the origin of humanity, it is beyond dispute that Africa was the homeland of our species and we are all in a sense Africans.
Culture and Evolution of Humans
The ability of H. sapiens to engage in long-range social interactions was key to the evolution of the species. This led to the accumulation of knowledge and practices, which was passed from one generation to another and this ultimately led to the development of culture.
This rock art in northern Africa dates from numerous periods and is significant because it shows the culture of ancient humans. (SteveStrummer / CC BY-SA 2.0)
This allowed them to survive and to flourish in the brutal environment of prehistoric Africa. Mark Thomas of the University of London, a researcher in genetics argues that “culture is our life-support system” according to The Guardian. The role of culture was essential to the evolution of H. sapiens and its success.
Anatomically modern humans did not appear in one place and then spread over Africa. Instead, we constantly evolved for almost half a million years in several locations in the continent in a complex process. This finding could revolutionize our understanding of early human evolution and also help us to understand what has made us so successful as a species.
Top image: Southwest Africa, one of the places of human origins. Source: mezzotint_fotolia / Adobe Stock.
By Ed Whelan