Scientists and experts have always been baffled by the origin of humans, and several studies were conducted leading to various theories. Their investigations were supported by evidence that comes in different forms. Using fossils that were discovered in different parts of the world, scientists were able to study the changes that happened in early humans.
One of the most commonly accepted theories is the out-of-Africa hypothesis which suggests that Homo sapiens came from a distinct ancestry of early humans before spreading throughout Europe and other parts of the world. However, as scientists use genetic sequencing in their investigation, more questions are raised and the result of a current studies leaves experts reconsidering the classic belief.
Tracing Our Origins
A group of researchers at McGill University and the University of California-Davis conducted a genomic study about the history of humans. They compared the genomes of 290 modern-day people in South Africa, Eurasia, and Ethiopia as well as the genetic data from British people. A study on ancient Neanderthal genome from Croatia was also included.
The team found out that the family tree is not a single straight line that traces back through a population that evolved, but a web connects a diversity of families across the regions in Africa. With the help of a model of continuous migration, they propose the idea that at least two main lineages are the origin of the genomes of the people living in Africa today. They represent populations of early humans who lived in various regions of the continent around 400, 000 years ago.
The model also suggests that the lineages evolved independently and merged until they fractured into subpopulations. Experts believe that this intertwined lineage could be the one who left Africa to settle in Europe, although that is not what the result of genome sequencing suggests.
The result of their study supports the multiregional hypothesis which proposes the idea that a continuous flow of gene happened between at least two different populations before leaving Africa for Europe. The merger events between the divergent populations may have been promoted by changes in wet and dry conditions across Africa between 140 000 years ago and 100 000 years ago.
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Reconciling the Theories
Scientists acknowledge the role of models in making inferences about human's deep history. For quite some time, a lot of people embraced the idea that Homo sapiens first emerged in East or Southern Africa.
However, population geneticist Brenna Henn from the University of California Davis suggests that "it has been difficult to reconcile these theories with the limited fossil and archaeological records of human occupation from sites as far afield as Morocco, Ethiopia, and South Africa which show that Homo sapiens were to be found living across the continent as far back as at least 300,000 years ago."
The oldest fossils that look like our modern species were discovered in several regions in Africa, and it still not clear which of them hosts the origin of mankind.
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