Our Ancestors First Appeared in Africa: Why There?
Modern humans inhabit every corner of the globe, and there is evidence that our ancestors, the Homo erectus, also first emerged in Africa. So, why did only the descendants of Homo erectus in Africa give rise to modern humans?
Every person on Earth can trace their ancestry back to Africa, where Homo sapiens emerged at least 300,000 years ago.
However, our ancestors, Homo erectus, lived throughout Africa, Europe, and Asia, and their descendant, Homo heidelbergensis, was also widespread.
Homo heidelbergensis gave rise to at least three branches in different regions: Neanderthals in Eurasia, Denisovans in Asia, and modern humans in Africa.
So, why did Homo heidelbergensis give rise to Homo sapiens in Africa?
Population geneticist Brenna Henn from the University of California, USA, stated, “This is a very puzzling question.” According to her, to answer this question, we first need to examine the early evolutionary processes of Homo sapiens.
A research study published in the journal Nature in 1987 gathered data showing that all modern human mitochondrial DNA originates from a population in Africa dating back 200,000 to 150,000 years.
However, geneticist Henn and other scientists question the perspective that only a single population gave rise to modern humans. When modern humans began to appear, our Homo sapiens ancestors lived scattered across dozens of distinct populations throughout Africa.
Africa is a vast continent with a highly diverse ecosystem, so these populations had to adapt to the specific conditions of their environments.
In a study published in Nature in 2023, Henn and her colleagues suggested that there were likely at least two of these populations that contributed to the ancestry of Homo sapiens.
Scientists believe that although these populations lived separately for thousands of years, each of them intermingled at some point, creating a common ancestral population that ultimately became modern humans.
Researchers surmise that the ecological diversity of the African continent and the subsequent mixing of multiple populations led to the evolution of modern humans.
Professor Curtis Marean, an anthropologist at the Institute of Human Origins, Arizona State University, noted that scientists have yet to reach a consensus on whether a single population or a few populations gave rise to modern humans.
However, he mentioned that these two hypotheses are more widely accepted than a newer hypothesis regarding intercontinental evolution in Africa.
The intercontinental hypothesis suggests that these human branches evolved simultaneously across the African continent. Professor Marean stated, “This does not fit with any evolutionary theory.” He concurred with geneticist Henn’s viewpoint that the vast expanse of Africa likely fostered genetic diversity, enabling modern humans to develop advanced cognition and social cooperation.
He explained that greater genetic diversity increases the potential for evolutionary advancements. Although both Europe and Asia combined also cover a vast area, the warm climate of Africa provided favorable conditions for Homo sapiens.
Severe cold climate phases occurred approximately every 100,000 years, limiting the evolution of populations in Eurasia, while African Homo sapiens lost very little of their living space during those times. With a broader range of connectivity, modern humans had more space to diversify and interact, facilitating greater gene flow.
“Studying human evolution is about understanding the processes that transformed us into who we are today. It’s hard to imagine anything more significant than that,” Professor Marean emphasized.
He stressed that all these observations are still theoretical, and much remains to be explored, such as which populations evolved into modern humans and whether language played a role in the cognitive development of modern humans. He hopes that future research will answer these questions.
