Pigs have spread across some of the largest natural barriers on Earth, appearing on islands where most mammals have never arrived. From Southeast Asia to the remote Pacific islands, they exist on both sides of the famous Wallace Line, a biogeographic boundary that typically stops wildlife in its tracks.
New genomic study published in Science shows why. By analyzing the DNA of more than 700 modern and archaeological pigs, researchers found that humans have been moving pigs throughout the Asia-Pacific region for tens of thousands of years. The results suggest that pig populations in the Pacific are the legacy of repeated human migrations – from early hunter-gatherers to agricultural societies – leaving behind genetic evidence that traces when, where and how people moved across the region's islands.
“It's very exciting that we can use ancient pig DNA to peel back the layers of human activity in this megabiodiverse region,” senior study author Laurent Franz said in the paper. press release.
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Early Pig People Transport
Ancient cave painting of a warty pig
(Adam Brumm (Griffith University) and Adhi Agus Octaviana (BRIN, Indonesia))
Genetic evidence suggests that humans began transporting pigs much earlier than previously thought. The study identifies populations living on Sulawesi – perhaps as far back as 50,000 years ago – as some of the earliest settlers. Known for producing some of the world's earliest rock art, these groups apparently transported native warty pigs to neighboring countries. islands such as Timor, potentially to create reliable sources of game.
These early movements indicate that pre-agricultural societies were already shaping island ecosystems by moving animals outside their natural ranges long before agriculture spread throughout the region.
“This research shows what happens when people move animals across vast distances across one of the world's most fundamental natural boundaries. These movements gave rise to pigs with melting pot ancestors. These patterns were technically very difficult to untangle, but ultimately helped us understand how and why animals ended up distributed across an area.” Pacific Islands“said the study's lead author, David Stanton.
Expansion of agriculture and pig farming
Pig movements intensified around 4,000 years ago as agricultural communities spread across the islands of Southeast Asia. According to the study, domestic pigs were transported along routes that began in Taiwan and extended through the Philippines and northern Indonesia before reaching Papua New Guinea, Vanuatu and eventually the outlying Polynesian islands.
Genomic evidence also points to the later introduction of pigs from Europe during the colonial era, further adding to the genetic complexity of pig populations in the region. Over thousands of years, these overlapping waves of movement gave rise to pig lineages shaped by multiple human cultures.
“Wild boars have spread throughout Eurasia and North Africa, and they certainly don't need the help of humans to help them spread into new areas. When humans had a hand, pigs were all too willing to disperse to newly colonized islands in Southeast Asia and the Pacific. By sequencing the genomes of ancient and more recent populations, we were able to link these human-assisted dispersals to specific human populations both in space and time,” said co-author Greger Larson.
Pigs in island ecosystems
Not everything has been transported pigs remained under human control. Many escaped and went feral, in some cases breeding with old lines of pigs that arrived on the islands thousands of years ago. For example, in the Komodo Islands, domestic pigs interbred with warty pigs originally brought from Sulawesi—animals that now serve as a key food source for the endangered Komodo dragon.
Today, throughout the Pacific, pigs serve a variety of roles. In some places they have spiritual significance, in others they are agricultural products, and in others they are destructive pests. On some islands, pigs have become so integrated into local ecosystems that their removal could trigger widespread environmental changes.
“The big question now is: at what point can we consider something family?” – said Franz. “What if humans introduced species tens of thousands of years ago [ago]are they worth the conservation effort?”
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