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Papua New Guinea Population Structure, Prion Disease Effects Characterized in Genetic Study

NEW YORK – New population genetic research has offered insights into historical events affecting population movements and interactions in the Eastern Highlands of Papua New Guinea (EHPNG), particularly the effects of a form of prion disease known as kuru.

A 20th-century kuru epidemic, which largely affected women and children from populations in the Fore and other linguistic groups, has been linked to "anthropophagic mortuary practices" in which deceased individuals were ritualistically consumed by their relatives after death, senior and corresponding author Simon Mead, a researcher affiliated with the University College London Medical Research Council Prion Unit, and his colleagues explained in a study published in the American Journal of Human Genetics on Tuesday.

Using array-based genotyping, researchers from UCL, the University of Copenhagen, and other centers in Australia and Papua New Guinea assessed genome-wide variant profiles in 943 individuals from 68 EHPNG villages, including representatives of 21 linguistic groups. Together with published genetic data for individuals in other parts of Papua New Guinea and beyond, the new genotypes provided a look at the genetic population structure within the EHPNG.

"The people of EHPNG are notable for their complex cultural and trade systems, cosmology, and linguistic diversity," the authors explained, adding that "[g]enetic data could help reveal how factors like linguistic diversity, cultural and agricultural practices, migration, and extreme geography can shape population genetic structure."

Although the EHPNG is home to extreme terrain, which is believed to have hindered easy movement between the region's 37 linguistic groups or clans, they explained, prior studies suggested that migration within the EHPNG has occurred, prompting interest in the region's population structure.

"The presence of non-Indigenous products in EHPNG evidence long-distance trade networks, proving EHPNG not to be completely isolated, and that trade may have led to genetic exchange," the authors reasoned, noting that "there are hypotheses of migration both within and into the region in the literature."

In particular, the results revealed pronounced population structures that broadly reflected linguistic relationships between the groups.

In addition, they saw enhanced female migration into certain villages that were particularly affected by kuru, a transmissible, often fatal neurodegenerative disease caused by consumption of tissue containing misfolded prion proteins. The overrepresentation of female migrants is suspected of reflecting efforts to replace women who had died from kuru due to their consumption of prion-affected tissues during mortuary feasts.

"While we observed a higher proportion of females among migrants relative to non-migrants throughout EHPNG, likely due to the general practice of patrilocality," the authors reported, "the largest and only significant skew toward female migrants was observed in areas of high kuru incidence."

"This observation is consistent with accounts from the region that notes during the epidemic the near absence of adult women in villages with high kuru incidence," they wrote, adding that "[m]en would frequently marry multiple times as a result of their previous wives dying from kuru, and strains were also placed on communities as a result of increased child care burden."

Moreover, the team's population structure analyses suggested that at least some of the seemingly distinct linguistic groups were either genetically linked to one another or showed incomplete genetic isolation, perhaps due to movement between nearby linguistic groups or shared cultural customs. Likewise, the population data pointed to more recent movement between relatively distant groups in the region, consistent with the presence of population dynamics that have stretched out over time.

Together, EHPNG population structure "reveals a complex multilayered set of factors that have caused high population differentiation, likely including both geographic and culture factors," the authors reported, adding that "the current population structure may still be evolving."

"This is another step in our long-term research endeavor to uncover how the Fore people and their neighbors survived kuru," Mead said in a statement. "It's also an important dataset that will help us further understand human history, because our knowledge about the populations in the region was scarce."