A new study shows that early humans actively avoided high-risk malaria areas for tens of thousands of years. This not only changed their migration and settlement routes, but also quietly reshaped the population pattern and genetic diversity in the history of human evolution. The research was completed in collaboration with the Max Planck Institute for Geoanthropology, the University of Cambridge and a number of institutions, and the relevant results have been published in the magazine "Science Advances".
For a long time, the scientific community has generally believed that modern humans did not originate from a single "cradle" in Africa, but came from a "puzzle" of multiple groups of people scattered across Africa that were interconnected and changed. Past explanations have looked to climate change as the dominant factor in explaining when and where these groups settled and how they interacted. The latest research suggests that infectious diseases such as malaria were also important forces in shaping the geographical distribution and evolutionary pattern of early humans.
Malaria is a parasitic disease transmitted by Anopheles mosquitoes. The main pathogen is Plasmodium falciparum. It can cause fever, anemia and even severe complications, posing strong and continuous selection pressure on human populations. The research team focused on the critical time window from about 74,000 to 5,000 years ago - this period was not only before humans left Africa on a large scale, but also before the emergence of agriculture and completely changed the ecology of malaria transmission.
To assess the long-term impact of malaria on human distribution, researchers constructed species distribution models of three major Anopheles mosquito complexes, combined with paleoclimate simulations and epidemiological data, to estimate potential malaria transmission risks in sub-Saharan Africa at different times. They then compared this risk map with the reconstructed "human ecological niche" to observe the spatial relationship between the scope of human activities and high-risk areas.
The results show that for at least the past 74,000 years, the risk level of malaria within the range of human activities has always been significantly lower than in surrounding areas "avoided" by humans. The researchers pointed out that this means that in early human history, areas with high malaria risk either had difficulty sustaining stable population settlements or were deliberately avoided, thus geographically "separating" different groups.
This seemingly slow and dispersed spatial separation effect has profoundly affected the contact, genetic exchange and migration paths between human populations over a long time scale, and ultimately contributed to the population structure and genetic diversity pattern of humans today. In other words, malaria was not only a health threat faced by early humans, but also a hidden driving force in human evolution.
Professor Andrea Manica of the University of Cambridge, co-author of the paper, said that malaria participated in shaping the spatial organization and population structure of modern humans by "segmenting" human society into different landscape units. Under this framework, traditional factors such as climate and topography are no longer sufficient to alone explain where humans can live. The risk of infectious diseases is also an important condition in determining the boundaries of human living space.
Professor Eleanor Scerri from the Max Planck Institute for Geoanthropology pointed out that this research opens up a new perspective for understanding human evolution. In the absence of genomic evidence for ancient pathogens from corresponding periods, the role of disease in our "deep history" is often underestimated. The latest results combine environmental modeling with human ecological niche reconstruction, providing a new framework for systematically exploring the relationship between diseases and human evolution.
The research team believes that with the accumulation of more ancient environment and ancient DNA data, it is expected to further analyze how infectious diseases such as malaria affect human migration, settlement distribution and gene flow patterns in different regions and on different time scales. This work will help us more fully understand why modern humans are distributed around the world in the way they are today, and what role disease played in this long evolutionary process.