A peer-reviewed study published in Proceedings of the National Academy of Sciences analyzed a newly sequenced 110,000-year-old Neanderthal genome extracted from a fossil in the Altai region. Researchers compared this high-coverage sequence with previously published genomes from three other Neanderthal individuals spanning 50,000 to 120,000 years ago. The methodology involved rigorous ancient DNA extraction protocols, alignment to the human reference genome, and population genetic modeling to estimate divergence times and gene flow. With an effective sample size of only four individuals total, the study is limited by the scarcity of well-preserved archaic specimens, potential DNA degradation over millennia, and the inability to capture full geographic diversity across Neanderthal range from Spain to Siberia. This is fully peer-reviewed work, not a preprint.

The findings show Neanderthal populations diverged into genetically distinct regional groups as early as 150,000 years ago, developing differences faster than seen in early modern human populations. This provides fresh insight into human evolutionary history by highlighting how archaic humans experienced repeated isolation events, likely driven by ice age climate fluctuations that created population refugia.

The original phys.org coverage accurately reports the early split but misses the broader implication: these isolated groups likely suffered intensified genetic bottlenecks, reducing adaptive potential. Original reporting also underplays how this challenges the assumption of widespread archaic interbreeding. While some gene flow occurred with early modern humans around 50,000-60,000 years ago, the new data suggests Neanderthal subgroups were already so differentiated that only specific populations contributed the 1-2% Neanderthal ancestry found in non-African modern humans today.

Synthesizing this with Prüfer et al.'s 2014 Nature paper on the Altai Neanderthal genome (which first quantified extremely low Neanderthal diversity) and the 2016 Nature study by Vernot and Akey on archaic admixture patterns, a clearer picture emerges. Neanderthals maintained effective population sizes below 5,000 for hundreds of thousands of years, making them vulnerable to inbreeding depression and local extinctions. Modern humans, by contrast, maintained larger, more connected networks after the out-of-Africa expansion, potentially explaining their persistence.

This pattern connects to the 'replacement' model of Neanderthal extinction around 40,000 years ago. Rather than simple competition, long-term isolation may have left Neanderthal groups less resilient to environmental shifts and incoming modern human populations. The study adds nuance to the narrative of seamless archaic-modern interactions, showing instead a fractured archaic world where genetic isolation was the norm, not the exception.