Short snouts and a flat profile: The German domestic pig looks very different today than 100 years ago. His skull shape has changed. The cause of this accelerated evolution is apparently man, as researchers have found. Accordingly, today’s snout shape of the pig has been an unintentional side effect of industrial -driven breeding since the beginning of the 20th century. One cause of the short focus could be to change the feed.
For several millennia we humans have kept domestic pigs as meat suppliers. But the farm animals did not always look the way we know them today. At the beginning of the domestication – and for some European breeds that were not crossed with races from Asia, even much later – the domestic pigs were more like the wild boar. Over time, the pigs got bigger, lost their black -brown bristles and developed a lighter skin.
Some properties were also targeted by selection in the course of globalization and the pursuit of efficiency: “At the beginning of the 20th century, the demand for pork in Germany increased significantly. Breeders were encouraged to optimize their animals: they should grow quickly, have good meat and be fertile, ”explains senior author Renate Schafberg from the Martin Luther University Halle-Wittenberg (MLU). But what effects did these breeding goals have on the physique of the pigs, especially the head? And how quickly did the changes occur?
Pork skull became shorter and flatter
A team around Schafberg and her colleague Ashleigh Haruda followed these questions. For this purpose, the researchers scanned the shape of 135 pigs from three breeds: German noble pig and German (refined) rural pig and wild boar as a comparison group. The team then reconstructed the head shape of the pigs and calculated geometric differences based on the scans. The skulls came from animals that lived in Germany either in the early 20th century or a few years ago. They were kept in the MLU pet collection and the Museum of Natural History in Berlin.
It showed that the snouts of today’s domestic pigs are significantly shorter and flatter than with wild boar and elderly. In addition, her forehead is flat and is no longer slightly arched like the wild boar – which now points the nose more forward than it before. Overall, the face is smaller and more compressed. “We had not expected that these differences are so clear in a period of 100 years,” says Schafberg. The period corresponds to about 100 generation of breeding.
What striking: In both domestic pig breeds, the skull shape has changed in the same way. The effect of German noble pigs is somewhat larger, but the principle is the same – although the two races were kept separately from each other for decades and although the skull features for breeding large, meat corners were unimportant. “Rather, the changes seem to be an unintentional by -product of the selection of the desired properties,” concludes Schafberg. Although the size, muscle and fat content counted for the breeders, both pig people developed a shorter point of view. But how did it come about?
Food as an evolutionary driver?
The researchers suspect that the short and flat skull shape could be a result of the diet. Since the food affects how strongly and quickly the animals grow, user pigs receive a completely different diet than their wild relatives. While wild boars are still omnivores and thereby developed a rather long snout, domestic pigs today receive primarily protein-rich concentrate pellets from grain and oil seeds. 100 years ago, however, domestic pigs did not live in stables and received waste from human food as food. Haruda and her colleagues suspect that the switch to troughs and concentrate could have made a long snout to chew, search for food and rummage in the earth. So far, this has not been proven.
The results show how much man can influence animals. “Charles Darwin assumed that big changes can only run over very long periods – over millions of years. Our work is further evidence that man can accelerate this process extremely through targeted breeding, ”says co-author Frank Steinheimer from the MLU.
Source: Ashleigh Haruda (Martin Luther University Halle-Wittenberg) et al.; Royal Society Open Science, DOI: 10.1098/RSOS.241039