A large-scale genomic study of over 1,500 individuals from 139 underrepresented Indigenous groups across northern Eurasia and the Americas sheds new light on the ancient migrations that shaped the genetic landscape of North and South America. The results reveal distinct ancestry patterns and early diversification of Indigenous South American populations. The late Pleistocene saw the migration of humans from North Asia into North and South America beginning by at least 23,000 years ago, according to archaeological evidence. This expansion was rapid – genetic evidence suggests northern and southern Native American groups began diverging between 17,500 and 14,600 years ago, with human presence in southernmost South America confirmed by 14,500 years ago. However, many questions remain about this expansion and its impact on the genetic architecture of human populations across the continents, especially in South America, where high-resolution genomic studies are still lacking.

To address this knowledge gap, Elena Gusareva and colleagues developed a comprehensive, high-resolution genomic dataset comprising over 1,500 individuals from 139 ethnic groups – many previously unstudied. This dataset, containing more than 50 million high-quality genetic variants, was analyzed alongside ancient and modern DNA from Native American populations. This helped the authors investigate deep patterns of population history, migration, and adaptation. Gusareva et al. found that Siberian populations trace their ancestry to six ancient lineages, with West Siberian heritage broadly shared across the region. A notable population decline around 10,000 years ago may have been driven by climate change and the loss of megafauna. Moreover, genetic and archaeological evidence suggests that Native Americans diverged from North Eurasians between 26,800 and 19,300 years ago, with west Beringian groups like the Inuit, Koryaks, and Luoravetlans being their closest living relatives. In South America, four distinct Indigenous lineages – Amazonians, Andeans, Chaco Amerindians, and Patagonians – rapidly emerged from a common Mesoamerican origin between 13,900 and 10,000 years ago. The four lineages largely reflect distinct geographical and environmental regions, such as the Andes Mountains, the arid lowlands of the Dry Chaco, the humid tropical rainforests of the Amazon Basin, and the frigid polar climate of Patagonia. According to the authors, rapid geographic isolation of these groups likely reduced genetic diversity, particularly in immune-related HLA genes, which may influence susceptibility to infectious diseases.

Mountain ecosystems may be more resilient to climate change than previously believed, according to a new study, which reports little empirical support for the widely recognized “escalator to extinction.” The findings challenge long-standing assumptions about range shift-driven extinction and instead introduce biotic homogenization as a more immediate concern facing mountain plants and animals. Mountain ecosystems worldwide are undergoing profound change due to rapid climate change. As temperatures increase, species are expected to shift their ranges upslope to take advantage of cooler habitats. However, while mountains offer vertical refuge for species adapting to climate change, their steep and confined topography limits how far some species can move, suggesting that climate warming may disproportionately threaten mountain biodiversity, especially species restricted to high elevations, narrow ranges, or tropical lowlands. This is sometimes described as the “escalator to extinction.” While some studies support this prediction, evidence remains inconclusive, especially for range shift gaps and lowland attrition. As such, the ecological consequences of climate warming in mountain regions are likely far more intricate than a uniform upward migration.

Using data from 8,800 records of historical and modern elevational range limits for over 2,000 animal and plant species across five continents, and a sophisticated Bayesian modeling approach, Chen et al. found little empirical support for predicted threats. Instead, the authors found that, despite ongoing climate warming, widespread range shift-driven extinctions in mountain ecosystems have not yet materialized. According to the findings, most species' elevational range shifts remain consistent with expectations shaped by the topographical constraints of mountain landscapes. Narrow-range species are expanding upslope without the hypothesized corresponding losses at their lower limits, countering previous assumed concerns about range shift gaps. Moreover, Chen et al. show that many lowland species are moving upslope without retreating from their lower boundaries, further challenging the prevailing view that tropical lowland species are confined to narrow thermal niches. One notable ecological signal the study revealed was growing biotic homogenization, wherein species communities across different elevations have become increasingly similar. This pattern, observed in several mountain regions, is likely driven by the upslope expansion of widespread lowland species alongside the decline of specialized, range-restricted taxa. According to the authors, this homogenization may foreshadow broader biodiversity losses and could disrupt ecological interactions in ways that reverberate through entire mountain ecosystems.