For tens of thousands of years, where humans have chosen to live has long been shaped by climate and the landscape. That's why there are so few of us clinging to the crags of Mount Everest or decamping to Antarctica. And the places we have called home in more welcoming parts of the world have helped shape our species — from our genes to our behaviors.
"How we became human is a story that played out over a very deep time scale and over a very big area," says Eleanor Scerri, an evolutionary archaeologist at the Max Planck Institute of Geoanthropology in Germany.
New work by Scerri and her colleagues considers an additional force that may have had a lasting influence — disease.
It's an area that's been hard to investigate since any genetic proof of particular pathogens would have degraded long ago.
In addition, "the majority of diseases will actually not leave a trace in the remains of an individual that died," says Andrea Manica, an evolutionary ecologist at the University of Cambridge.
Using a different approach, these researchers say that mosquito-borne malaria may have been a powerful sculptor of where early humans settled across sub-Saharan Africa.
In new work published in the journal Science Advances, they present evidence that human populations appear to have avoided malaria hotspots starting at least 74,000 years ago. Then, around some 15,000 years ago, a key mutation arose in West Africa that afforded people some protection against the disease, allowing them to expand where they lived.
"I feel like it's a first step to explore further what are the interactions between human[s] and diseases in the past," says lead author and evolutionary ecologist Margherita Colucci.
A surprisingly strong signal
The research team took advantage of a set of climate models they developed for sub-Saharan Africa looking back over the last 74,000 years — "the same that we use to predict climate change but in this case applied to the past," says Manica.
"We can actually reconstruct the temperature, the precipitation, the type of vegetation that would grow in various parts of Africa," he continues.
With that information, the researchers could then predict where certain species of mosquitoes would have preferred to live over time based on their modern habitats. Like today, these mosquitoes carried and transmitted malaria, a potentially lethal disease.
They studied their collection of maps that showed "where we expect the probability of high risk of malaria," says Colucci.
"And if it was there, it would have been a big problem," adds Manica.
The research team then considered where people were living over that same time period based on archaeological evidence of human settlements.
And that's when they saw their striking result: for tens of thousands of years, people didn't tend to live in malaria hotspots.
"What we don't know is whether they were avoiding them or whether they were going there and dying," says Manica, "but basically they were just not persisting in the areas where malaria would have been really problematic."
"In science, you rarely get such a strong signal," Scerri says. "We just looked at each other and went like, 'Oh wow, it's there.'"
A mutation that stood up to malaria
The results suggested that malaria had helped to shape human settlement patterns in the past, bringing populations together at times and separating them on other occasions.
What if, however, ancient humans and mosquitoes simply preferred different climate conditions, so their geography would have had nothing to do with malaria? This seems unlikely, based on another observation.
Manica says that some 15,000 years ago, people's avoidance of the regions with the disease began to break down. And it's around this time when a key genetic mutation arose in West Africa — sickle cell anemia. Two copies of the gene are fatal, but one offers a critical degree of protection against malaria.
"That solution was so important," he says, "it opened up a whole area of Africa that before was very challenging. That tells us just how important malaria was in the past."
The findings resonate with other archaeological artifacts that suggest a long history of humans battling bugs, including the use of natural insect repellents like red ochre and plants with insecticidal properties. "I think we're just scratching the surface here," says Scerri.
Simon Underdown is a biological anthropologist at Oxford Brookes University who wasn't involved in the research. "What the paper neatly shows is disease, it's always been an issue for humans," he says. "It shapes how we live. Disease is a big deal."
He argues that these results offer not only a window into the past, but also the future, as disease-carrying mosquitoes expand their range in today's changing climate.
"You can't suddenly evolve sickle cell," says Underdown. "That takes time. But what humans do, we can come up with cultural solutions to biological problems."
He's referring to antidotes like vaccines or anti-malarials since solving problems turns out to be rather human as well.
Copyright 2026 NPR
