SRINAGAR: A cave in Ladakh is so narrow in places that its innermost chamber has a ceiling just 50 centimeters tall. For centuries, local communities used the site, known as Old Lady Spider Cave, to lay their dead to rest, and bones still cover parts of its floor today. Now, ancient DNA recovered from those remains is reshaping what scientists understand about one of the least-studied corners of human genetic history.
A study published in the journal Science Advances reports genome-wide DNA data from 10 individuals buried in the cave, called Abi Srinjamo Bao in the local language, at a site 4,000 meters above sea level near the village of Yogma Kharbu. Radiocarbon dating puts the remains at roughly 1,500 years old.
The more striking finding concerns where their ancestors came from. Their genomes show close to an even split between ancestry tied to present-day North Indian populations and ancestry closely related to ancient Tibetans. This combination is rare among South Asians today.
Using a statistical method that measures the length of DNA segments inherited from each ancestral group (segments that shrink with every passing generation as chromosomes recombine), the researchers determined that this mixing began at least 50 generations before the individuals were born. That places the first contact between the two ancestral groups at roughly 2,800 years ago, far older than archaeological and linguistic evidence had previously suggested for such deep interaction between Tibetan and South Asian peoples.
A Landscape at Crossroads
Ladakh sits at a natural crossroads, positioned between the Tibetan Plateau, Central Asian trade routes through the Tarim Basin and the Hindukush-Pamir mountains, and the South Asian subcontinent. Petroglyphs found across the region trace connections to Bronze Age Central Asian cultures and later to Iron Age steppe traditions.
Pottery unearthed in western Ladakh, where the cave is located, includes red-slipped vessels with shapes and decorations linked to the Hellenistic, Kushan and post-Kushan periods, further evidence of long contact with cultures to the west. What had been missing was direct genetic proof of when, and how extensively, people from the Tibetan Plateau and the South Asian mainland actually interbred.
The excavation that recovered the samples took place in 2021, led by archaeologists Veena Mushrif-Tripathy and Quentin Devers under the auspices of India's Archaeological Survey. Genetic analysis was then carried out by a team at Harvard University headed by geneticists Nick Patterson and David Reich.
Bones, Genomes and Mapping
The bones, representing men, women, infants and elders, were found densely scattered across two of the cave's chambers. Some remains had naturally mummified skin, ligaments and muscle still attached, including two intact mummified hands, preserved by the site's cold, dry, high-altitude conditions.
The cave has drawn visitors for centuries, disturbing its contents over time. Even so, the researchers managed to extract usable DNA from eight bones and three soft-tissue samples, together representing 10 distinct individuals.
To reconstruct ancestry, the team compared the ancient genomes against a large reference panel of modern populations, including Tibetans, Han Chinese and more than a thousand individuals spanning what geneticists call the Indian Cline, a well-documented genetic gradient running across South Asia.
Jammu Dogra Link
Plotted on a standard genetic map, seven of the best-preserved genomes fell neatly along a line connecting Tibetan populations to North Indian groups such as Dogra and North Indian Brahmins, a pattern typical of direct admixture between two source populations.
Follow-up statistical modeling confirmed that a roughly 50-50 mixture fit the data well. The researchers note, though, that the precise ancient Tibetan population involved does not perfectly match any Tibetan genomes currently available for comparison, suggesting a still-unsampled population somewhere on the plateau.
Only two present-day groups show a similar ancestry profile: the Minero and Balti communities, both from Ladakh. Statistical modeling suggests Minero individuals derive more than half of their ancestry, and Balti individuals nearly half, from a source much like the ancient cave population, indicating the lineage persisted, increasingly diluted, into people living in the region today.
Dogra, a community from the Jammu region, plays a particular role in this part of the story. In the researchers' broader genetic comparisons, Dogra sits at the same point on the South Asian ancestry gradient as North Indian Brahmin groups, right where the South Asian half of the Old Ladakh mixture points to.
When the team modeled the ancestry of living Minero and Balti communities, they used Dogra as the modern stand-in for that South Asian component, pairing it with ancestry drawn from the ancient cave population itself.
That modeling fit well. Minero came out as roughly 56 percent Old Ladakh-related ancestry and 44 percent Dogra-related, and Balti as roughly 45 percent Old Ladakh-related and 55 percent Dogra-related.
The pattern suggests the ancient admixed lineage did not simply fade out. It persisted as a distinct, identifiable ancestry component that continued mixing with incoming Dogra-related ancestry from farther south over the following centuries, producing the range of Tibetan-to-South-Asian proportions seen across Ladakhi groups today.
Sole Eurasian Link
The team also examined lineages preserved in mitochondrial DNA and the Y chromosome, which are passed down maternally and paternally. Most matched expectations for either South Asian or Tibetan ancestry.
One result stood out. A pair of closely related individuals in the cave carried a mitochondrial lineage called U5a1d1, which is rare in South Asia today but common among ancient populations from the Caucasus and the Lower Volga region of Eastern Europe. The researchers suspect this lineage reached North India generations earlier, carried by people connected to Eurasian steppe migrations, before eventually making its way to Ladakh.
In a final analysis, the researchers screened the ancient genomes for a well-known gene variant, inherited from Denisovans, that helps modern Tibetans tolerate low oxygen levels at extreme altitude. Denisovans were an extinct population closely related to Neanderthals that interbred with early modern humans.
Roughly half of sampled ancient Tibetan genomes carry this variant, and since the Old Ladakh individuals derive about half their ancestry from Tibetan sources, the researchers expected to find it on roughly a quarter of the chromosomes they examined. They found it on just one of nine. That is not statistically surprising given the small sample size, though it suggests the trait faced no strong selective pressure in this population after the two ancestries mixed.
The findings matter well beyond Ladakh's remote valleys. Ancient DNA research has transformed scientific understanding of population movements across Europe, Central Asia and East Asia over the past two decades, but South Asia has lagged behind, with comparatively few ancient genomes recovered so far. Hot, humid conditions across much of the subcontinent tend to break down DNA faster than cooler climates do.
Ladakh's cold, dry, high-altitude environment, the same conditions that preserved the cave's mummified tissue, offers researchers a rare window into a part of the world whose genetic past has largely stayed hidden.
Blending May Be Before Migration
The researchers are careful to note that the admixture itself did not necessarily happen in Ladakh. It could, they write, have occurred elsewhere, in what is now Nepal, for instance, before the resulting population migrated into the mountains. They also stress that the ancient Tibetan population involved remains unsampled, meaning parts of the story are still missing.
The Old Ladakh individuals themselves lived only shortly before the Tibetan Empire rose to power on the plateau in the seventh century, the researchers note, making their remains among the earliest direct genetic evidence of an established Tibetan-South Asian community in the high Himalayas. But the deeper history written into their DNA reaches back much further.
The blending of Tibetan and South Asian ancestry that produced their genomes began nearly 2,800 years ago, the study concludes, long before any written record from the region survives.
Future excavations, the authors write, will be needed to determine how far this ancient, genetically distinctive population spread across the Himalayas, and how long it endured before being absorbed into the diverse communities that call the region home today.
Yes — Dogra shows up in two distinct places in the paper, doing slightly different jobs.
In the principal components analysis, Dogra (a community from the Jammu region of Jammu and Kashmir) is one of the reference populations marking the South Asian end of the "Indian Cline." The ancient Old Ladakh individuals, along with modern Minero and Balti, fall along a line running from Tibetans to a single point on that cline occupied jointly by Dogra and North Indian Brahmin groups — meaning Dogra-related ancestry sits right where the South Asian half of the Old Ladakh mixture points to.
Dogra's bigger role, though, is in modeling the two living populations, Minero and Balti, rather than the ancient cave individuals themselves (those were modeled using North Indian Brahmin groups instead). Using Dogra as the modern stand-in for South Asian ancestry, the team modeled Minero as about 56% ancestry related to the ancient Old Ladakh population and 44% Dogra-related, a good statistical fit (P = 0.24). Balti came out at roughly 45% Old Ladakh–related and 55% Dogra-related, a weaker but still workable fit (P = 0.04).
The upshot: the 2,800-year-old admixed lineage didn't just fade away. It persisted as a distinct, identifiable ancestry component that kept mixing with incoming Dogra-related ancestry from further south over the following centuries, which is what produces the spread of Tibetan-to-South Asian proportions seen across Ladakhi groups today.
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