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   PID: hpt/lnx 1.9.0-cur 2019-01-08   
   TID: hpt/lnx 1.9.0-cur 2019-01-08   
    Woolly mammoths evolved smaller ears and woolier coats over the 700,000   
   years that they roamed the Siberian steppes    
      
     Date:   
         April 7, 2023   
     Source:   
         Cell Press   
     Summary:   
         A team of researchers compared the genomes of woolly mammoths   
         with modern day elephants to find out what made woolly mammoths   
         unique, both as individuals and as a species. The investigators   
         report that many of the woolly mammoth's trademark features --   
         including their woolly coats and large fat deposits -- were already   
         genetically encoded in the earliest woolly mammoths, but these and   
         other traits became more defined over the species' 700,000+ year   
         existence. They also identified a gene with several mutations that   
         may have been responsible for the woolly mammoth's miniscule ears.   
      
      
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   FULL STORY   
   ==========================================================================   
   A team of researchers compared the genomes of woolly mammoths with modern   
   day elephants to find out what made woolly mammoths unique, both as   
   individuals and as a species. The investigators report April 7 in the   
   journal Current Biology that many of the woolly mammoth's trademark   
   features -- including their woolly coats and large fat deposits --   
   were already genetically encoded in the earliest woolly mammoths, but   
   these and other traits became more defined over the species' 700,000+   
   year existence. They also identified a gene with several mutations that   
   may have been responsible for the woolly mammoth's miniscule ears.   
      
      
   ==========================================================================   
   "We wanted to know what makes a mammoth a woolly mammoth," says   
   paleogeneticist and first author David Di'ez-del-Molino of the Centre   
   for Palaeogenetics in Stockholm. "Woolly mammoths have some very   
   characteristic morphological features, like their thick fur and small   
   ears, that you obviously expect based on what frozen specimens look   
   like, but there are also many other adaptations like fat metabolism and   
   cold perception that are not so evident because they're at the molecular   
   level."  To identify genes that were "highly evolved" in woolly mammoths   
   -- meaning they had accrued a large number of mutations -- the team   
   compared the genomes of 23 Siberian woolly mammoth with 28 modern-day   
   Asian and African elephant genomes.   
      
   Twenty-two of these woolly mammoths were relatively modern, having   
   lived within the past 100,000 years, and sixteen of the genomes had   
   not been previously sequenced. The twenty-third woolly mammoth genome   
   belonged to one of the oldest known woolly mammoths, Chukochya, who   
   lived approximately 700,000 years ago.   
      
   "Having the Chukochya genome allowed us to identify a number of genes   
   that evolved during the lifespan of the woolly mammoth as a species,"   
   says senior author Love Dale'n, professor of evolutionary genomics at   
   the Centre for Palaeogenetics in Stockholm. "This allows us to study   
   evolution in real time, and we can say these specific mutations are   
   unique to woolly mammoths, and they didn't exist in its ancestors."   
   Not surprisingly, many genes that were adaptive for woolly mammoths are   
   related to living in cold environments. Some of these genes are shared   
   by unrelated modern-day Arctic mammals. "We found some highly evolved   
   genes related to fat metabolism and storage that are also found in   
   other Arctic species like reindeer and polar bears, which means there's   
   probably convergent evolution for these genes in cold-adapted mammals,"   
   says Di'ez-del-Molino.   
      
   While previous studies have looked at the genomes of one or two woolly   
   mammoths, this is the first comparison of a large number of mammoth   
   genomes.   
      
   This large sample size enabled the team to identify genes that were   
   common among all woolly mammoths, and therefore likely adaptive, as   
   opposed to genetic mutations that might only have been present in a   
   single individual.   
      
   "We found that some of the genes that were previously thought to be   
   special for woolly mammoths are actually variable between mammoths,   
   which means they probably weren't as important," says Di'ez-del-Molino.   
      
   Overall, the 700,000-year-old Chukochya genome shared approximately 91.7%   
   of the mutations that caused protein-coding changes in the more modern   
   woolly mammoths. This means that many of the woolly mammoth's defining   
   traits - - including thick fur, fat metabolism, and cold-perception   
   abilities -- were probably already present when the woolly mammoth first   
   diverged from its ancestor, the steppe mammoth.   
      
   However, these traits developed further in Chukochya's descendants. "The   
   very earliest woolly mammoths weren't fully evolved," says Dale'n "They   
   possibly had larger ears, and their wool was different -- perhaps less   
   insulating and fluffy compared to later woolly mammoths."  More modern   
   woolly mammoths also had several immune mutations in T cell antigens   
   that were not seen in their ancestor. The authors speculate that these   
   mutations may have conferred enhanced cell-mediated immunity in response   
   to emerging viral pathogens.   
      
   Working with ancient mammoth DNA comes with a slew of hurdles. "Every   
   step of the way, things are a bit more difficult, from fieldwork, to   
   lab work, to bioinformatics," says Di'ez-del-Molino.   
      
   "Apart from the field work, where we have to battle both polar bears and   
   mosquitos, another aspect that makes this much more difficult is that   
   you have to work in an ancient DNA laboratory, and that means that you   
   have to dress up in this full-body suit with a hood and face mask and   
   visor and double gloves, so doing the lab work is rather uncomfortable   
   to put it mildly," says Dale'n.   
      
   "I would like to highlight Marianne Dehasque, the second author of this   
   paper, who did the herculean effort of performing lab work on most of   
   these samples."  All the mammoths whose genomes were included in this   
   study were collected in Siberia, but the researchers hope to branch out   
   and compare North American woolly mammoths in the future. "We showed a   
   couple of years ago that there was gene flow between woolly mammoths   
   and the ancestors of Colombian mammoths, so that's something that we   
   will need to account for because North American woolly mammoths might   
   have been carrying non-woolly mammoth genes as well," says Dale'n.   
      
       * RELATED_TOPICS   
             o Plants_&_Animals   
                   # Evolutionary_Biology # Mammals # Genetics   
             o Earth_&_Climate   
                   # Tundra # Snow_and_Avalanches # Climate   
             o Fossils_&_Ruins   
                   # Early_Mammals # Paleontology # Evolution   
       * RELATED_TERMS   
             o Mastodon o Mammoth o Domestic_sheep o Flying_squirrel o   
             Evolution o Japanese_Crane o Homo_ergaster o Neanderthal   
      
   ==========================================================================   
   Story Source: Materials provided by Cell_Press. Note: Content may be   
   edited for style and length.   
      
      
   ==========================================================================   
   Journal Reference:   
      1. David Di'ez-del-Molino, Marianne Dehasque, J. Camilo Chaco'n-Duque,   
         Patri'cia Pečnerova', Alexei Tikhonov, Albert Protopopov,   
         Valeri Plotnikov, Foteini Kanellidou, Pavel Nikolskiy, Peter   
         Mortensen, Gleb K.   
      
         Danilov, Sergey Vartanyan, M. Thomas P. Gilbert, Adrian M. Lister,   
         Peter D. Heintzman, Tom van der Valk, Love Dale'n. Genomics of   
         adaptive evolution in the woolly mammoth. Current Biology, 2023;   
         DOI: 10.1016/ j.cub.2023.03.084   
   ==========================================================================   
      
   Link to news story:   
   https://www.sciencedaily.com/releases/2023/04/230407110720.htm   
      
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