The monk seal, decimated during Antiquity

Mediterranean monk seal, in 2004.

Lumans are great predators, this no longer needs to be demonstrated. The sixth mass extinction testifies, before our eyes, to what our way of life inflicts on other species. However Sapiens did not wait for the Anthropocene to carry out its macabre task. Scientists have shown it: some 14,000 years ago, our ancestors, having just arrived in North America, eradicated woolly mammoths and wild horses. At the other end of the hemisphere, this time 40,000 years ago, they had done the same with the fifty or so species of marsupials and giant monotremes that then lived in Australia.

The Mediterranean monk seals had a slightly less dire fate. The International Union for Conservation of Nature (IUCN) has even removed the species from the category "critically endangered", after several rebounds recorded in the Atlantic and in the eastern Mediterranean. Nevertheless: with less than 500 adults listed and sometimes isolated groups, the pinniped remains “in danger of extinction”. In other words, in an eminently fragile situation. No doubt it should be noted here that the monk seal, so named for its tendency to live isolated and in caves, should not be confused with gray seals, harbor seals, and other pinnipeds of cold seas – including Brittany and the Somme. . He swims in warm water, with a subspecies in Hawaii and another in a few pockets of our Big Blue. “Yet in the past, they were present everywhere from the Black Sea to the North Atlanticinsists Philippe Gaubert, research fellow at the Institute for Research and Development (IRD). We wanted to know how we got there. »

Passing through the sieve of genetics

To conduct this investigation, he and his colleague Jordi Salmona, also a researcher at the Evolution and Biological Diversity Laboratory (attached to the IRD, Toulouse) set up an international team to pass a large sample through a genetic sieve. For this, they were able to benefit from 20 tissues from ancient animals (until 1830) and 314 necropsies carried out between 1989 and 2020. The results, published on August 31 in the journal of the Royal Society, Proceedings B, are uplifting.

Biologists have found in the markers certain field observations: “There are indeed three distinct populations, one in the eastern Mediterranean, Greece, Turkey, Cyprus; another off Western Sahara; a third in Madeira », says Jordi Salmona. A fourth, once housed in the western Mediterranean, may be extinct. These populations testify, between them, to a genetic continuity, "but also, each one, of a very low diversity", continues the researcher. In Madeira, the twenty adult individuals would even present a “worrying inbreeding”.

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