Imagine a researcher waiting for a mosquito that doesn’t want to bite her at night while perched in a tree in Borneo. The mosquitoes she needs, the ones that favor monkeys over people, won’t approach. Living higher up in the forest canopy, they use techniques unrelated to human scent to track their primate hosts, and gathering them necessitates either waiting for larvae under trees or simply giving up and returning home.
In the meantime, a different group of mosquitoes—the ones that have evolved over millions of years to find human blood irresistible—are following her whereabouts with what seems, in the dark, to be personal hostility. This is the actual nature of tropical paleoentomology fieldwork. Not a laboratory. Not a neat series of steps that make sense. In a forest where some of the most significant periods of human evolution may have occurred, a scientist in a tree is being ignored by an insect she has spent years attempting to comprehend.
| Field | Details |
|---|---|
| Study Topic | Evolution of human blood-feeding preference in Anopheles leucosphyrus mosquito group |
| Published | February 26, 2026 — Scientific Reports |
| Lead Author | Upasana Shyamsunder Singh — Postdoctoral Scholar, Vanderbilt University, Nashville, Tennessee |
| Co-Author | Catherine Walton — Senior Lecturer, Earth & Environmental Sciences, University of Manchester, UK |
| Mosquito Species Sequenced | 38 specimens across 11 species within the Leucosphyrus group |
| Fieldwork Period | 1992–2020 across Southeast Asia (including Borneo, Northeast India) |
| Key Region | Sundaland — Java, Sumatra, Borneo, Malay Peninsula |
| Human Preference Evolved | Between 2.9 million and 1.6 million years ago |
| Hominin Likely Present | Homo erectus — possibly in Southeast Asia ~1.8 million years ago |
| Known Mosquito Species | 3,500+ globally; human blood-feeding is rare across species |
| Reference Website | Scientific Reports – Nature Portfolio |
The study that resulted from years of such work—collecting mosquito specimens throughout Southeast Asia between 1992 and 2020—was published in Scientific Reports in February 2026, and its implications go far beyond entomology. The DNA of 38 mosquitoes from 11 species in the Anopheles leucosphyrus group—a group of Southeast Asian mosquitoes that includes species that can spread malaria—was sequenced by a team led by Upasana Shyamsunder Singh at Vanderbilt University and Catherine Walton at the University of Manchester.
They posed a seemingly straightforward question: when did some of these mosquitoes begin biting humans instead of monkeys? Reconstructed using genetic mutation estimates and computer modeling, the answer was approximately 2.9 million to 1.6 million years ago. This window significantly overlaps with the time when early hominins, possibly Homo erectus, are believed to have arrived in the Sundaland region, which includes what is now Java, Sumatra, Borneo, and the Malay Peninsula.
It is difficult to overestimate the importance of that timing, and the explanation raises one of paleoanthropology’s more enduring annoyances. There is actually very little evidence of early human migration into Southeast Asia in the fossil record. Decomposition is accelerated in humid tropical climates; bone, wood, and organic materials decompose rapidly in mosquito-friendly conditions that are terrible for preservation. For decades, scientists have been debating whether Homo erectus arrived in the area approximately 1.8 million or 1.3 million years ago.
There is so little physical evidence to support either side of the debate that serious scientists can legitimately support both positions. The debate is not conclusively settled by the mosquito study. However, it adds a data point from a completely unexpected direction, implying that early hominins were sufficiently prevalent in Sundaland to cause a dietary shift in a group of insects that had previously only eaten nonhuman primates. It turns out that mosquitoes do not alter their dietary preferences in response to small or unstable prey populations. There had to be a large number of hominins.
It’s worthwhile to consider the evolutionary reasoning underlying the change. For millions of years, Sundaland was covered in a thick tropical rainforest, which gave the modern Leucosphyrus group’s primate-biting ancestors a stable home. Then, about two million years ago, the climate started to change. Cooler, drier cycles produced more open forest and sporadic grasslands, which may have made it easier for early human populations to migrate across the region.
In the very slow and unconscious way that evolution makes decisions, a mosquito species confronting a new environment and the presence of a new primate had two options: either continue biting the monkeys as they retreated farther into the remaining forest or adjust to the newcomers who were now traveling through the open terrain. A few lineages made the decision to adapt. Singh, Walton, and their colleagues are now reading the genetic record of that decision, preserved in the DNA of mosquitoes gathered over thirty years of meticulous fieldwork, like a biological diary of ancient human presence.
Researchers like David Reed at the Florida Museum of Natural History have been arguing for years that parasites and pests that track humans closely preserve their own record of that relationship in their genomes, which is what makes this approach truly exciting. As Reed has pointed out, the DNA of head lice contains an entirely different account of the history of human migration.
This theory is extended into deep time by the mosquito work, which implies that under certain conditions, the evolutionary reactions of blood-feeding insects may be able to preserve information about the presence of hominins that the physical environment has long since destroyed. It’s a sort of roundabout archive, flawed in its own ways but providing perspectives that stone tools and bones just can’t match.
The researchers are appropriately cautious about the limitations of what can be inferred from this data. The genetic models used have their own uncertainties, and the window of 2.9 million to 1.6 million years is wide. It’s possible that a related lineage whose fossils have not yet been discovered, rather than Homo erectus, was the hominin presence that caused the mosquito shift.
The agreement between the genetic timeline and the archaeological theories is suggestive rather than definitive, and Walton herself has stated that convergence—the discovery that several independent lines of evidence point to the same area and roughly the same time period—is what makes the overall picture more likely than any one line of evidence could. Even though none of the individual sources are conclusive, it is significant when hominin fossils, mosquito DNA, and climate modeling all point to the same time and location.
The fact that the insect that has killed more people than any other species in history has, in a different way, been one of the more faithful witnesses to the earliest movements of our species is hard to ignore. Evolutionary history didn’t matter to the mosquito.
Finding a blood meal was important to it. However, it encoded a memory of that encounter in its genome when it adapted to the hominins passing through Sundaland almost two million years ago. This memory has persisted to this day, waiting to be read by researchers who are prepared to spend enough nights in enough trees to gather the evidence. It is important to recognize the insect’s and the researchers’ perseverance.
