A separate older ghost lineage inferred from Oceanian genomes suggests another ancient contributor to Denisovan-derived regions, potentially dating back around 1.77 million years and possibly related to Homo erectus, with no sequenced genome for confirmation.

The findings, published in Science, signal broad implications for understanding human evolution and disease adaptation, highlighting deep ancestral contributions that persist in living genomes.

All estimates are model-dependent, contingent on thresholds for branch age, segment length, mutation rate, generation time, and population size, meaning different models could yield different percentages.

Evidence points to ancient admixture in Africa before the major Out-of-Africa migration, but identifying the exact ancestral populations requires more data, especially ancient African genomes or protein remains for confirmation.

The first unidentified lineage is inferred from unusually long ancestral branches in genealogies, indicating deep divergence followed by later reintroduction through interbreeding rather than continuous presence.

While the signal is widespread, the study does not specify the identity, date, or precise origin of the contributing population, and multiple scenarios could explain the pattern within Africa’s population structure.

Two ghost lineages are implicated in shaping modern human genomes: an older African lineage possibly linked to Homo heidelbergensis or related groups and an older Eurasian lineage that contributed via Denisovans, though no DNA from these lineages has been recovered.

A 2026 TRACE-based study estimates that an unknown deeply separated human lineage contributed about 0.49% to 1.1% of genomes across multiple populations, with traces found in both Africans and non-Africans.

The study emphasizes a methodological shift: living genomes can reveal evidence of ancestral populations whose DNA is not present in modern samples, supporting a reticulate view of human evolution rather than a simple ladder-like model.

TRACE detects ghost ancestry by analyzing ancestral recombination graphs and long-evolving segments, enabling the reconstruction of missing ancient lineages without ancient DNA.

A new computer-based method, TRACE, analyzes modern genomes to infer ghost archaic contributions and reconstruct hidden ancestral lineages.

UC Berkeley researchers used TRACE to infer ghost archaic contributions in 503 modern human genomes without needing ancient DNA.