Scientists have always been better at telling you what they found than explaining what wasn’t there. A skull can be dated. A burial site can be excavated. A stone tool can be mapped to a culture, a region, a thousand-year window of human activity. What doesn’t leave a trace in the ground is a population that lived and died without leaving bones or artifacts behind – one that exists only as a faint pattern encoded in the DNA of its distant descendants. Genetics has a word for these populations. It calls them ghost lineages, and for more than a decade, researchers studying Indigenous American genomes have known that at least one such ghost was in the data, leaving its mark on people in the Amazon basin and the Andes while remaining completely absent from the fossil record. The question was never whether it was real. The question was what, exactly, it was.
A major new genomic study published in April 2026 in Nature has brought that ghost into sharper focus than ever before. Researchers sequenced 128 high-coverage Indigenous American genomes and found they harbor extensive and previously uncharacterized genetic diversity, reflecting at least three dispersals into South America, followed by regional differentiation and long-term continuity. The scope of the work, and the sophistication of what it uncovered, has forced scientists to revise some of their most foundational assumptions about how, when, and by whom the Americas were populated.
The findings arrive at a moment when the scientific community is reckoning honestly with a chronic blind spot. Indigenous peoples of the Americas represent the last principal expansion of humans across the globe, yet their genetic history remains one of the least explored, and their evolutionary history largely unresolved, owing to the limited availability of genomic data. This study is an attempt to change that – and its conclusions reach far deeper into the past than many researchers expected.
The Study Behind the Discovery
An international team of scientists detailed findings from the Indigenous American Genomic Diversity Project, which analyzed 128 genomes from people living in Argentina, Bolivia, Brazil, Colombia, Ecuador, Mexico, Paraguay, and Peru – an investigation that included 45 populations and 28 language families. The project did not operate at arm’s length from the communities it studied. As reported by ASU News, lead researcher Tábita Hünemeier, a geneticist at the University of São Paulo and the Institute of Evolutionary Biology, collaborated with researchers and Indigenous communities across Latin America to sequence 128 whole genomes from living people from north Mexico to southern Argentina.
The team combined new data with previously sequenced genomes for a total of 199 contemporary Indigenous individuals from 53 populations and 31 linguistic families, also incorporating ancient DNA to provide what the researchers describe as the most comprehensive view of Indigenous American genomic diversity and evolutionary history to date.
The scale matters. By analyzing the Indigenous genomes, researchers were able to identify more than a million genetic variants that have not been found in other populations. Many of those variants have potential biomedical significance – and their existence in global databases was, until now, a blank space.
Three Waves, Not Two
For decades, the prevailing model of South American settlement held that two waves of migration from Asia, crossing the land bridge of Beringia into North America and gradually moving south, explained the genetic makeup of the continent’s Indigenous peoples. Scientists had long suspected that humans settled South America in two waves – one about 15,000 years ago, followed by another roughly 9,000 years ago. The new study complicates that picture substantially.
With few exceptions, most Indigenous peoples in the Americas trace their ancestry to a migration that occurred about 15,000 years ago. After entering North America, these early populations rapidly expanded across the continent. Around 9,000 years ago, a second wave of migration partially replaced earlier groups. Now, for the first time, researchers have identified evidence of a third wave, occurring roughly 1,300 years ago, when Indigenous populations moved from Mesoamerica into South America and the Caribbean.
The genetic signature of this third dispersal appears in present-day South American populations and in ancient Caribbean remains. The timing has drawn inevitable comparisons to major events in Mesoamerican history – the decline of Teotihuacan between approximately A.D. 650 and 750 falls within the same approximate window – but the researchers have been careful not to overstate the connection. This relatively recent migration was probably not spurred by a single event but was rather a more gradual process, one that involved increasing connectivity and gene flow between Mesoamerica, the Caribbean and South America across several centuries, according to study co-author Hünemeier.
The newcomers show hints of being related to Mesoamericans from Mexico and Central America, but researchers don’t yet know exactly where they came from or who their closest relatives were. Without the source population and more direct evidence from ancient DNA, it remains difficult to fully characterize how and when this third migration occurred.
The complementary research reinforces the picture. As Science/AAAS reports, Cosimo Posth, an archaeogeneticist at the University of Tübingen who was not involved with the Nature paper, noted that the genetic diversity present before colonialism is largely lost, making it harder for scientists to appreciate South America’s complex population history – which makes resurface efforts like this “an extremely important” undertaking. His team published a complementary study in Current Biology finding evidence of unexpected genetic diversity and otherwise invisible migrations in 52 ancient genomes from Argentina and Uruguay.
The Ghost in the Genome: Ypykuéra
The third migration wave is significant, but it is arguably the second major finding of the study that carries the greater weight of mystery. Buried within the DNA of some Indigenous South Americans is a genetic signal that does not trace back to any known, physically documented population on earth.
The genetic analysis revealed traces of an ancient Asian “ghost lineage” that contributed genes to both Indigenous Americans and early Australasians. This signal, which the researchers call Ypykuéra – meaning “ancestor” in the Indigenous Tupi language of Brazil – has been present at low but consistent levels in Indigenous people for more than 10,000 years. Although the genetic signal of Ypykuéra has been found in modern people, no fossil evidence of the group has been discovered yet.
Around 2 percent of the genome in some Indigenous South Americans shows genetic affinity with populations in Australasia, including those in Australia, New Guinea, and the Andaman Islands. This connection, present in South American individuals dating back more than 10,000 years and in very similar proportions, suggests the influence of an ancient, unsampled Asian population known as Ypykuéra, which intermixed with the ancestors of these populations.
The question of why this signal has persisted so consistently – at roughly the same proportional levels across highly distinct populations – is one the study addresses with cautious optimism. According to David Comas, principal investigator at the Institute of Evolutionary Biology and professor at the Universitat Pompeu Fabra, “the frequency of this Ypykuéra ancestry is very similar across the different populations analyzed, perhaps indicating a certain adaptive advantage in some of these genomic regions.” A signal this stable across millennia and thousands of miles of geographic separation is not what you would expect from genetic drift alone. Something in those variants may have been genuinely useful to the people carrying them.
Some of the genes that persisted in Indigenous populations were those associated with immune function, energy metabolism, fertility, fetal growth and malaria protection, revealing that diverse biological processes were shaped by natural selection. Some of these genes were found to be shared with modern Australasian populations, suggesting several ancient Ypykuéra traits were positively selected to help Indigenous Americans thrive in a new environment.
The researchers are not claiming certainty here – natural selection is notoriously difficult to prove from genomic data alone, and Hünemeier has emphasized that the hypothesis needs further testing. But the consistency of the signal is difficult to explain any other way.
Archaic Ancestry: Neanderthals and Denisovans
The Ypykuéra signal is not the only ancient inheritance embedded in these genomes. The study also confirms that between 1 and 3 percent of the genome comes from archaic hominids, such as Neanderthals and Denisovans – a proportion similar to that seen in other regions globally – and that these hominids contributed genetic variants that proved key to adaptation on the American continent, as evidenced by signs of natural selection found in the genome.
This is a finding that echoes broader patterns in human genetics. Most people outside of sub-Saharan Africa carry a small percentage of Neanderthal DNA from ancient interbreeding events, a discovery that has fundamentally reshaped how scientists understand the boundaries between archaic and modern human populations. What the new Indigenous American genomic data reveals is that the same layered complexity applies in the Americas – and that the archaic inheritance present in these populations has a distinctive regional pattern of its own. The study found it was not simply a residue of ancestry but an active contributor to how people survived and reproduced in diverse American environments, from high-altitude Andean plateaus to tropical lowland forests.
For readers interested in how ancient DNA is reshaping our understanding of human health today, this research connects directly to broader questions about why medical genetics still lags for most of the world’s populations – a topic explored in this 2025 cholesterol research and the gap between which discoveries reach which communities.
The Colonial Bottleneck and What Was Lost
The study does not only describe what was found. It also documents, with precision, what was taken.
Across the Americas, Indigenous peoples experienced a drastic population decline estimated between 40 and 90 percent, driven by epidemics introduced from Europe and Africa, enslavement, and conquest. These forces created evolutionary bottlenecks that still shape genetic diversity today. The genetic record captured in both ancient remains and living descendants reflects deep-time migrations and regional interconnections, as well as the severe disruptions of the colonial era, which continue to constrain the range of Indigenous genetic variation.
The scientists found evidence of a genetic bottleneck caused by European colonization that led to the “widespread extermination” of Indigenous populations over the past 500 years. Today, the genetic diversity of Indigenous Americans is a fraction of what it was before the arrival of Europeans.
The implications of that loss are not only historical. Understanding the unique genetic variations that likely resulted from Indigenous populations adapting to the diverse environments and conditions of the Americas “could improve medical research and promote more equitable health care,” as the study co-authors note in an accompanying research briefing in Nature. What was lost in the colonial era was not only lives, languages, and cultural systems. It was also a vast archive of human genetic diversity – much of which can never be recovered.
Why Indigenous Populations Have Been Left Out of Genomic Research
The gap between what scientists know about European and non-European genomes is not accidental. It reflects decades of research investment concentrated in wealthy nations and institutions with easy access to willing participants from majority populations. According to Roderic Guigó, a researcher with the Center for Genomic Regulation who was not involved with the study, “genomic data is heavily biased toward populations of European origin because biological samples are mostly obtained from individuals of this ancestry.”
The consequences are concrete. An overwhelming 76 percent of participants in clinical trials between 2015 and 2019 were of primarily European descent, according to data from the US Food and Drug Administration. As a result, most data used to inform drug development is likely derived from European populations and extrapolated to individuals of other ancestries.
This is the structural context into which the Indigenous American Genomic Diversity Project steps. As study co-author Carlos Eduardo G. Amorim of Arizona State University has stated, “Genetic information from Indigenous American populations is essential because these groups have been historically underrepresented in genomic research, leaving major gaps in our understanding of human diversity, evolution and health.”
The inclusion of Indigenous populations in genomic research is not just about understanding the past – it has vital implications for the future. By identifying previously unknown genetic variants with medical relevance, this dataset creates opportunities to improve biomedical research, disease prevention, and drug design for Indigenous communities and the global population alike.
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What the Ghost Has Always Been Telling Us
The April 2026 Nature study representing the Indigenous American Genomic Diversity Project is, by any measure, a landmark piece of science. It delivers the largest genomic dataset of Indigenous American populations ever assembled, identifies more than a million previously undocumented genetic variants, uncovers a third and previously unknown migration into South America from Mesoamerica approximately 1,300 years ago, and confirms the persistent presence of the Ypykuéra ghost lineage – an ancient Asian population that has never been found in the fossil record but has left its genetic mark on Indigenous South Americans for more than 10,000 years.
Each of those findings stands on its own. Together, they describe a picture of human prehistory in the Americas that is far more layered, more interconnected, and more ancient than the two-wave model allowed. The first people to cross Beringia were not the last to shape who came after them. There were multiple movements, multiple mixings, and multiple inherited legacies – including from populations whose bones may never be found.
What the study also makes visible is the cost of decades of scientific neglect. The genetic diversity of Indigenous Americans, already catastrophically reduced by colonization, has also been systematically overlooked by a research enterprise built around European data. The more than one million newly identified genetic variants in this dataset are not just scientifically interesting – they are evidence of everything the field has been getting wrong by looking only at one slice of humanity and calling it universal. That this research was conducted in partnership with Indigenous communities, rather than extractively, points toward what a more equitable model of genomic science could look like. The ghost lineage has a name now. The question is what science does with the knowledge that it has been there all along.
AI Disclaimer: This article was created with the assistance of AI tools and reviewed by a human editor.