For more than two centuries, naturalists have been trying to solve some mysteries about the origin and movement of some animals. Among them, for example, is a question that has long troubled biogeographers: how wild pigs breed Potamochoerus exceed Mozambique Channel starting from Africa and arriving at the island Madagascar?
A team consisting of a large number of researchers decided to answer this question for the first time apply genomics in biogeographic research about the evolution of these wild pigs, with surprising results that were published in a study in the journal The nature of communication.
According to these findings, Madagascar’s history is too old for ancestral pigs to have been trapped on the island when it overtook Africa. Madagascar was actually born about 160 million years ago, more than 150 million years before the first pigs appeared on Earth. This therefore led to the idea that pigs gen Potamochoerus they only recently arrived on the island, perhaps by swimming and joining some islands that have now disappeared.
But the biggest problem is that the Mozambique Channel is 400 kilometers long and there are almost no islands to allow the animals to reach Madagascar in stages. In the depths of the canal, geologists also found nothing that could indicate the ancient existence of a land bridge. 400 kilometers is really a bit too much for it to be possible to imagine a pig capable of crossing them even with the help of a drifting raft.
“However, our study contradicts the view of previous research that showed pigs arrived in Madagascar via swimming 480,000 years ago. Rasmus Heller, lead author of the study and associate professor at Department of Biology, University of Copenhagen. – In our opinion, actually a wild boar of the genus Potamochoerus it was only introduced to Madagascar by man about 1,000-5,000 years ago after an attempted domestication. And the main species present on the island is not the most common one, but the one that comes from southern Africa.”
By sequencing the genomes of 67 different individuals from different regions of East Africa and Madagascar, Heller clarified that there are mainly two species of pigs in the area, and that both have a very different history than one might think. THE common potamocers (Potamochoerus larvatus), mainly found in East/Southern Africa, e.g red potamocers or with bunches (Potamochoerus porcus), found in Central/West Africa, have not only confused biologists for years due to their anatomical similarities. They are also capable of natural interbreeding and give life to hybrids.
Hybrids are larger than their parent species and appear tamer. Important features when planning to cross the Indian Ocean in an attempt to reach a very remote but resource rich island. “Although scientists have tried very hard to determine the differences between the two species and to understand which of them reached Madagascar first, today we know that their biological separation is incomplete and that their hybrids were probably bred by humans, to be further investigated, ” he explained. Laura D. Bertolapostdoctoral fellow at the University of Copenhagen and another lead author of the study.
So scientists have spent years asking the wrong questions. It was not so important to understand which of the many African pigs arrived in Madagascar first and what anatomical differences made it possible to recognize the species. It was important to find out when people started to domesticate these creatures, this was not always possible, and to transfer them elsewhere.
“Genomic data can provide us with information about biodiversity patterns at a much higher resolution than was previously possible,” the biologists further explain. For example, biogeographers have tried for years to determine the detailed structure of the various African populations of this genus Potamochoerus, without succeeding on anatomical differences alone. However, gene sequencing has made it much easier to observe the flow and selection of genes from population to population and to gain better information about the evolutionary and expansion patterns of different species and hybrids.
Furthermore, although in the past scientists believed that pigs were able to cross the Mozambique Channel, millennia before the advent of navigation and man, no paleontological finding has ever been found to support this theory. “The old biogeographers who based their research only on anatomy will now have to recognize that wild pigs are a recent species from Madagascar and that the other questions that research will now have to ask are different – he explains Renzo F. Balboa, another researcher who contributed to the study. – Who brought these animals to Madagascar? What was their origin? Did they speak Bantu, Austronesian, or both? Did they know that the wild boars inhabiting their territory belonged to two different species, or did they marry the hybrids just because they were bigger? Did they manage to tame them completely? Those are the questions we have to address now.”