Extinctions Heal Slowly

first_imgThe history of life on Earth has been a heated tug of war between forces that power the birth of new species and those that grind life forms into oblivion. Now a new study suggests that while extinction rates vary widely, origination rates march to their own slow drummer. The study, published in the 3 January issue of Nature, fuels fears that it will take millions of years for biological diversity to recover from the current wave of human-caused extinctions.In recent years scientists have challenged a long-held assumption that evolution’s pace can accelerate to fill the biological holes caused by episodic mass extinctions. Last year, a pair of researchers reported that it takes about 10 million years for evolution to renew the planet’s biodiversity following an extinction event, whether that event is large or small. Building on that finding, one team member, earth scientist James Kirchner at the University of California, Berkeley, decided to compare rates of extinction to rates of origination over a 500-million-year period.To compare evolutionary clocks, Kirchner turned to the same database he’d analyzed earlier: the late Jack Sepkoski’s encyclopedic compilation of marine animal fossils, which spans a 540-million-year history and lists the first and last known occurrences of about 4500 families and 36,000 genera. To untangle such a massive and uneven database, Kirchner used a specialized form of a mathematical technique called spectral analysis, which was developed by astrophysicists to make sense of the complex light signals received from distant stars. Kirchner concluded that extinction rates are up to two and a half times more variable than origination rates, with originations of new species pulling ahead of extinctions only when researchers look at chunks of time greater than 25 million years. The finding is further proof that “while extinction rates can spike, diversification rates can’t rev up to offset them,” Kirchner says.Sign up for our daily newsletterGet more great content like this delivered right to you!Country *AfghanistanAland IslandsAlbaniaAlgeriaAndorraAngolaAnguillaAntarcticaAntigua and BarbudaArgentinaArmeniaArubaAustraliaAustriaAzerbaijanBahamasBahrainBangladeshBarbadosBelarusBelgiumBelizeBeninBermudaBhutanBolivia, Plurinational State ofBonaire, Sint Eustatius and SabaBosnia and HerzegovinaBotswanaBouvet IslandBrazilBritish Indian Ocean TerritoryBrunei DarussalamBulgariaBurkina FasoBurundiCambodiaCameroonCanadaCape VerdeCayman IslandsCentral African RepublicChadChileChinaChristmas IslandCocos (Keeling) IslandsColombiaComorosCongoCongo, The Democratic Republic of theCook IslandsCosta RicaCote D’IvoireCroatiaCubaCuraçaoCyprusCzech RepublicDenmarkDjiboutiDominicaDominican RepublicEcuadorEgyptEl SalvadorEquatorial GuineaEritreaEstoniaEthiopiaFalkland Islands (Malvinas)Faroe IslandsFijiFinlandFranceFrench GuianaFrench PolynesiaFrench Southern TerritoriesGabonGambiaGeorgiaGermanyGhanaGibraltarGreeceGreenlandGrenadaGuadeloupeGuatemalaGuernseyGuineaGuinea-BissauGuyanaHaitiHeard Island and Mcdonald IslandsHoly See (Vatican City State)HondurasHong KongHungaryIcelandIndiaIndonesiaIran, Islamic Republic ofIraqIrelandIsle of ManIsraelItalyJamaicaJapanJerseyJordanKazakhstanKenyaKiribatiKorea, Democratic People’s Republic ofKorea, Republic ofKuwaitKyrgyzstanLao People’s Democratic RepublicLatviaLebanonLesothoLiberiaLibyan Arab JamahiriyaLiechtensteinLithuaniaLuxembourgMacaoMacedonia, The Former Yugoslav Republic ofMadagascarMalawiMalaysiaMaldivesMaliMaltaMartiniqueMauritaniaMauritiusMayotteMexicoMoldova, Republic ofMonacoMongoliaMontenegroMontserratMoroccoMozambiqueMyanmarNamibiaNauruNepalNetherlandsNew CaledoniaNew ZealandNicaraguaNigerNigeriaNiueNorfolk IslandNorwayOmanPakistanPalestinianPanamaPapua New GuineaParaguayPeruPhilippinesPitcairnPolandPortugalQatarReunionRomaniaRussian FederationRWANDASaint Barthélemy Saint Helena, Ascension and Tristan da CunhaSaint Kitts and NevisSaint LuciaSaint Martin (French part)Saint Pierre and MiquelonSaint Vincent and the GrenadinesSamoaSan MarinoSao Tome and PrincipeSaudi ArabiaSenegalSerbiaSeychellesSierra LeoneSingaporeSint Maarten (Dutch part)SlovakiaSloveniaSolomon IslandsSomaliaSouth AfricaSouth Georgia and the South Sandwich IslandsSouth SudanSpainSri LankaSudanSurinameSvalbard and Jan MayenSwazilandSwedenSwitzerlandSyrian Arab RepublicTaiwanTajikistanTanzania, United Republic ofThailandTimor-LesteTogoTokelauTongaTrinidad and TobagoTunisiaTurkeyTurkmenistanTurks and Caicos IslandsTuvaluUgandaUkraineUnited Arab EmiratesUnited KingdomUnited StatesUruguayUzbekistanVanuatuVenezuela, Bolivarian Republic ofVietnamVirgin Islands, BritishWallis and FutunaWestern SaharaYemenZambiaZimbabweI also wish to receive emails from AAAS/Science and Science advertisers, including information on products, services and special offers which may include but are not limited to news, careers information & upcoming events.Required fields are included by an asterisk(*)The work supports the emerging view that “origination and extinction are decidedly different processes determined by different rules,” says Arnold I. Miller, a paleobiologist at the University of Cincinnati in Ohio. But Douglas Erwin, a paleobiologist at the Smithsonian’s National Museum of Natural History in Washington, D.C., says he’s “leery about the analytical structure of the study,” because it’s based on an outdated version of the time scale that accompanies Sepkoski’s database. “I’m not sure that the analysis is sufficiently robust to support the conclusions,” says Erwin.Related sites Last year’s paper by Kirchner and a colleague, showing it takes 10 million years for biodiversity to be renewed following an extinction event Commentary by Douglas Erwin on that paper Milwaukee Public Museum’s Geologic Time Scale Diversity Through Time graphic based on Sepkoski’s workCycles of mass and minor extinctions on Earth, from the Hooper Virtual Paleontological Museumlast_img

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