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Swedish Wild Boar Populations Pointed to Multiple Origins, With No Domestic-Pig Ancestry Detected

Wild boar walking in forest habitat in Bavarian Forest National Park, Germany
Research · Genetics & genomics

A genetic study of wild boar (Sus scrofa) in Sweden found that the present population is not genetically uniform and showed no evidence of recent introgression from Swedish domestic pigs. The results indicate that wild boar in different parts of Sweden descend from more than one external source population.

The researchers genotyped 107 wild boar from Skåne, Blekinge, Södermanland and Uppland using an 80K SNP chip, which tests tens of thousands of single-letter DNA variants across the genome, and compared them with 427 Swedish domestic pigs. After genetic quality control, 50 wild-boar samples representing all four regions and 322 domestic-pig samples remained for the main analyses. Animals from Skåne and Blekinge formed the same genetic group, while Södermanland and Uppland each formed separate clusters.

Wild boar showed no recent domestic-pig ancestry

Principal-component and genetic-differentiation analyses separated the Swedish wild boar from the domestic pigs. An ancestry analysis likewise found no clear evidence of detectable genetic introgression — domestic-pig DNA entering the wild-boar gene pool through hybridisation and subsequent breeding — in the sampled populations. The authors note that small or older contributions from domestic pigs could still be difficult to detect, especially if the contributing pig breed was not represented in the comparison data. Comparisons with wild boar elsewhere in Europe showed that Swedish regional groups were most similar to different European populations.

Multiple origins likely shaped the modern population

Wild boar disappeared from Sweden in the 17th century and became established again after animals escaped from enclosures during the 1970s and 1980s. Because the origin of those animals was not documented, the genetic differences among the present regional populations provide evidence that the re-established Swedish population has multiple external origins rather than a single common source.

Sources and image credit

  1. Johansson, A. M., Dalin, A.-M., Jonas, E., Mikko, S., & Malmsten, A. (2026). Wild or tame? In search for the genetic origin of wild boar (Sus scrofa) in Sweden. Ecology and Evolution, 16(4), e73369.Primary peer-reviewed open-access study, first published 3 April 2026. The study genotyped 107 Swedish wild boar and 427 Swedish domestic pigs; Swedish wild boar formed three regional genetic groups and no clear introgression from Swedish domestic pigs was detected.

Image: Simon Waldherr — wild boar in Bavarian Forest National Park, Germany, photographed 16 May 2020; representative species image. Source: Wikimedia Commons. · CC BY-SA 4.0 · Source

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