RSS: #przewalski

#przewalski

  • @simplicissimus
    Simplicissimus
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    @odilon
    @touti
    @palestine___________
    @02myseenthis01
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    Il n’existe plus de chevaux sauvages | Pour la Science
    ▻https://www.pourlascience.fr/sd/zoologie/il-nexiste-plus-de-chevaux-sauvages-12967.php

    https://medias.pourlascience.fr/api/v1/images/view/5a9d37058fe56f390d08f226/wide_1300/image.jpg

    Le cheval de #Przewalski, un cheval archaïque découvert en Mongolie en 1879, passait pour la seule espèce sauvage de cheval encore en vie. Les travaux de Ludovic Orlando, du CNRS et de l’Université Paul Sabatier à Toulouse, viennent de révéler que ce n’est pas le cas : c’est un cheval domestiqué retourné à la vie sauvage. En outre, nos chevaux domestiques actuels ne descendent pas de cette première population chevaline domestiquée connue,.
    La domestication du cheval s’est produite entre le IVe et le IIIe millénaire avant notre ère, durant à l’âge du Cuivre (Chalcolithique). Les plus anciens indices proviennent d’une culture de chasseurs de chevaux présente au nord du Kazakhstan actuel, il y a 5 500 ans : la culture de Botaï.
    […]
    Qu’en ressort-il ? Deux résultats inattendus. Pour commencer, il s’avère que les chevaux de Botaï ne sont pas les ancêtres des chevaux actuels, mais qu’ils sont les ancêtres directs des chevaux de Przewalski. Ainsi, ces chevaux qui passaient pour sauvages ne le sont pas. Ce sont des équidés féraux, c’est-à-dire domestiqués puis retournées à la vie sauvage.
    […]
    Le deuxième résultat inattendu est qu’il va falloir rechercher l’origine de nos chevaux ailleurs que dans la culture de Botaï. En effet, aucun des 22 génomes de chevaux eurasiatiques séquencés par l’équipe de Ludovic Orlando ne s’est avéré apparenté aux chevaux de Botaï. Au moins un autre foyer de domestication a donc existé. Reste à le trouver. En Anatolie, en Asie centrale, mais aussi dans les steppes pontiques, de vastes régions de l’est de l’Ukraine et de la Russie méridionale où les cultures cavalières des Scythes et des Sarmates ont prospéré dans l’Antiquité.

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  • @nautilus
    nautilus [RSS]
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    @kassem
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    What’s Worse: Unwanted Mutations or Unwanted Humans? - Facts So Romantic
    ▻http://nautil.us/blog/whats-worse-unwanted-mutations-or-unwanted-humans

    http://static.nautil.us/3655_310cc7ca5a76a446f85c1a0d641ba96d.jpg

    Two of the rare Przewalski’s horses that now roam the area near the Chernobyl nuclear plant.Sergey GaschakAfter a fatal series of errors and malfunctions in the early morning of April 26, 1986, the core of the Chernobyl nuclear facility melted down and then exploded, killing 31 workers at the plant. The accident spewed massive amounts of radioactive material into the surrounding area, forcing a mass evacuation of the nearby villages. Many wild animals died from the direct toxicity of the radiation and almost 1,000 acres of the Red Forest—named for the unusual color its trees turned after the disaster—died within months. The most radioactive human settlements were bulldozed and buried. (See the related story about the most radioactive part of the nuclear plant: “Chernobyl’s Hot Mess, ‘the (...)

    nautilus [RSS]
    • @simplicissimus
      Simplicissimus

      Many of the most radioactive isotopes have decayed or washed out of the region in rain. Birds, rodents, elk, lynxes, wolves, wild boar, and deer have all been spotted living within the borders of the zone. A herd of 21 rare Przewalski’s horses that had escaped from the quarantined area were found to be living in the region. By early 2005, the herd had grown to 64.
      (…)
      Some scientists, including Texas Tech University professor Robert Baker, say that removing the human populations has had the unintentional effect of creating a wildlife reserve. “It cannot be said that radiation is good for wildlife,” Baker writes on his research website. “[But] it can be said that the world’s worst nuclear power plant disaster is not as destructive to wildlife populations as are normal human activities.”

      But some researchers disagree, arguing that the evidence that wildlife is thriving is merely anecdotal. Other studies have shown that animals and the ecosystem continue to be affected by the radiation.
      (…)
      But Mousseau also recently found that some birds appear to have developed the ability to adapt to their radioactive environment better than others. After taking blood and feather samples from 152 birds from 16 different species at eight sites, they found that birds with a certain type of pigment in their feathers (pheomelanin) were in poorer health. This was because the production of pheomelanin was using up many of the antioxidants in the birds’ bodies. Usually antioxidants help protect animals from dangerous free radicals caused by radiation. But if the antioxidant levels are too low, free radicals can cause genetic damage and oxidative stress, when they overwhelm the body’s defenses. Mousseau found that the two species of birds that used pheomelanin to produce a lot of pink pigment failed to adapt to their Chernobyl home. The other species didn’t use up their antioxidants making melanin; they could fight off the stress of radiation and were in better health.
      (…)
      While scientists don’t agree on whether Chernobyl deserves its unofficial title of “wildlife refuge,” the research shows that different species react differently to chronic exposure to radiation. For at least some of them, it’s worth bearing a few extra mutations to once again have access to a land untrammeled by humans.

      #Przewalski #takhi

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