A new study suggests that for the last 74,000 years, malaria shaped where early humans could live in Africa-fragmenting populations and influencing patterns of genetic exchange long before recorded history.
Increasing evidence suggests that our species emerged through interactions between populations living in different parts of Africa, rather than from a single birthplace. Until now, however, most explanations for how those populations were distributed across the continent have focused on climate alone. The new research shows that disease-specifically malaria-also played a crucial role.
In a paper published this week in Science Advances, researchers from the Max Planck Institute of Geoanthropology, the University of Cambridge, and colleagues including Dr James Blinkhorn from the University of Liverpool investigated whether Plasmodium falciparum malaria shaped human habitat choice between 74,000 and 5,000 years ago, the critical period before humans dispersed widely beyond Africa and before agriculture dramatically altered malaria transmission.
The study shows that malaria, one of humanity's oldest and most persistent pathogens, influenced habitat choice by pushing human groups away from high-risk environments and separating populations across the landscape. Over tens of thousands of years, this fragmentation shaped how populations met, mixed, and exchanged genes, helping create the population structure seen in humans today. The findings suggest that infectious disease was not simply a challenge early humans faced: it was a fundamental factor shaping the deep history of our species.
"We used species distribution models of three major mosquito complexes together with palaeoclimate models," explains lead author Dr Margherita Colucci of the Max Planck Institute of Geoanthropology and the University of Cambridge. "Combining these with epidemiological data allowed us to estimate malaria transmission risk across sub-Saharan Africa."
The researchers then compared these estimates with an independent reconstruction of the human ecological niche across the same region and time period. The results show that humans strongly avoided, or were unable to persist, in areas with high malaria transmission risk.
"The effects of these choices shaped human demography for the last 74,000 years, and likely much earlier," says Professor Andrea Manica of the University of Cambridge, one of the senior authors of the study. "By fragmenting human societies across the landscape, malaria contributed to the population structure we see today. Climate and physical barriers were not the only forces shaping where human populations could live."
"This study opens up new frontiers in research on human evolution," adds Professor Eleanor Scerri of the Max Planck Institute of Geoanthropology, also senior author of the study. "Disease has rarely been considered a major factor shaping the earliest prehistory of our species, and without ancient DNA from these periods it has been difficult to test. Our research changes that narrative and provides a new framework for exploring the role of disease in deep human history."
Dr James Blinkhorn said: "Through innovative application of modelling work, this study places emphasis on the role of disease to understand what shaped human demography in our deep past. Unfortunately, the impacts of disease in the deep past can be very ephemeral, prohibiting comparative studies with evidence of past human distributions or their climatic context. It was a truly interdisciplinary effort, bringing together specialists in epidemiology, palaeoenvironmental studies, palaeoecological modelling, and archaeologists, like myself, to bring together the different strands of evidence necessary to tackle this topic and to reveal the enduring impact that malaria has had on the distribution of our species in Africa."
Click here to access the full article: Malaria shaped human spatial organisation for the last 74 thousand years
Photo credit: A long-exposure photo of a mosquito - the main vector of malaria - in flight, by Martin and Ondrej Pelanek
