Selective breeding over the past century has shortened and flattened the snouts of German domestic pigs. Though not an intentional trait selection, these changes resulted from breeding for growth and fertility, possibly influenced by diet. The study highlights how humans can accelerate evolution far more quickly than previously thought.
Short snouts and a flat profile—within just 100 years, humans have significantly altered the skull shape of German domestic pigs. According to a team from Martin Luther University Halle-Wittenberg (MLU), this change is likely due to new breeding practices introduced in the early 20th century. Their findings, published in the journal Royal Society Open Science, are based on an analysis of 3D scans from 135 skulls of wild boars and domestic pigs from both the early 20th and 21st centuries. Surprisingly, similar changes were observed even in species that were kept separately.
Humans have been raising pigs as livestock for centuries, during which time the animals have undergone significant transformations. For example, they have grown larger and lost their black and brown bristles, along with their darker skin tones.
“The demand for pork in Germany increased significantly at the beginning of the 20th century and breeders were encouraged to optimise their animals. They needed them to grow quickly, provide good meat, and be fertile,” explains Dr Renate Schafberg, Head of the Domestic Animal Collection at MLU. For the current study, she and Dr Ashleigh Haruda from Oxford University analyzed 135 skulls from three different breeds: Deutsches Edelschwein, Deutsches Landschwein – and wild boars, who acted as a control group. The skulls were either from the early 20th century or were only a few years old.
Unintended Changes in Skull Shape
The two domestic pig breeds exhibited significant changes: the animals’ snouts became significantly shorter and flatter, while the skulls of the more contemporary animals no longer had a slightly outwardly curved forehead. “We didn’t expect such pronounced differences to appear within a span of only 100 years,” says Schafberg. Remarkably, both breeds of domestic pig underwent the same changes, despite being kept separately. “These changes occurred even though breeders did not select the animals specifically for their skull shape, as this trait was not important for breeding. Instead, the changes appear to be an unintended by-product of selecting the desired traits,” says Schafberg.
Another reason for the alterations could be related to changes in the animals’ diet. Nutrition is known to influence the growth and development of animals. Today, pigs are mainly fed pellets that are high in protein. In contrast, the skulls of wild boars, who remain omnivores, have not undergone such changes.
The findings demonstrate how strongly humans can influence the evolution of animals. “Charles Darwin assumed that long periods of time – millions of years – are required for major changes to take place. Our work is further proof that humans can greatly accelerate this process through selective breeding,” says co-author Dr Frank Steinheimer, Head of the Central Repository of Natural Science Collections at MLU.
Reference: “Evolution under intensive industrial breeding: skull size and shape comparison between historic and modern pig lineages” by A. Haruda, A. Evin, F. Steinheimer and R. Schafberg, 1 February 2025, Royal Society Open Science.
DOI: 10.1098/rsos.241039
The study was funded by the German Federal Ministry of Education and Research (BMBF) and the European Research Council (ERC).
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