{"id":136675,"date":"2010-08-16T12:38:03","date_gmt":"2010-08-16T11:38:03","guid":{"rendered":"http:\/\/www.madrimasd.org\/blogs\/universo\/?p=136675"},"modified":"2010-08-16T12:38:58","modified_gmt":"2010-08-16T11:38:58","slug":"la-cultura-de-los-indios-clovis-extincion-de-la-megafauna-y-los-paisajes-de-suelos","status":"publish","type":"post","link":"https:\/\/www.madrimasd.org\/blogs\/universo\/2010\/08\/16\/136675","title":{"rendered":"La Cultura de los Indios Clovis, Extinci\u00f3n de la Megafauna y los Paisajes de Suelos"},"content":{"rendered":"

Durante el final de la \u00faltima glaciaci\u00f3n cuaternaria <\/strong><\/span>se produjeron varias pulsaciones clim\u00e1ticas enormemente bruscas fri\u00f3-calor-fr\u00edo-calor, hasta entrar en el Holoceno, en donde r\u00e1pidamente surgi\u00f3 la agricultura (Neol\u00edtico). Hablamos de\u00a0 las pulsaci\u00f3nes del Dryas antiguo y reciente<\/a>. Como ver\u00e9is pinchando en este \u00faltimo enlace, existen teor\u00edas para todos los gustos a la hora de explicar la raz\u00f3n de cambios clim\u00e1ticos tan abruptos<\/strong><\/span>. \u00a1Y como no!, ya que los mamut norteamericanos desaparecieron durante ese evento<\/strong><\/span> (junto con otros grandes mam\u00edferos como los cam\u00e9lidos), <\/strong><\/span>los climat\u00f3filos actuales vuelven la vista a las grandes emisiones de metano que deb\u00edan petar tales enormes bestias<\/span><\/strong> al recorrer las \u00bfpraderas? Cuando desaparecieron el gas de marras pudo descender sus concentraciones en la atm\u00f3sfera, dando lugar al Dryas reciente. Ya que por all\u00ed, ya pululaba la cultura de los indios Clovis<\/a>, cazadores de estos gigantes lanudos, mutatis mutandis<\/em>, ahora ciertos \u201cexpertos claman, que esta cultura ind\u00edgena fue la inductora de la gran primera crisis clim\u00e1tica causada por la humanidad<\/strong><\/span>. As\u00ed, como casi siempre, se barre para la casa del T\u00edo Sam.\u00a0 \u201cLa Gran Crisis de la Flatulenta<\/strong>\u201d<\/span> (hoy padecemos la fraudulenta). \u00bfQui\u00e9n ha dicho que el hedor es malo? \u00bfQui\u00e9n defiende ahora la bondad de los Clovis, por cuya causa se extingui\u00f3 la megafauna, el clima se congel\u00f3, etc. ?<\/p>\n

\"tigres-con-dientes-de-sable-norteamarica-fuente-anthropology-net\"\u00a0<\/p>\n

Tigres con diente de sable en las grandes llanuras americanas<\/a>. Fuente: Anthropology.net<\/a><\/p>\n

<\/p>\n

\u00a0La investigadora Felisa, como ver\u00e9is en la noticia que hoy reproducimos de Terradaily<\/strong><\/span>, avala la argumentaci\u00f3n expresada en el p\u00e1rrafo anterior. Empero en los otros enlaces ya expuestos, se defienden causas alternativas tan razonables como<\/span><\/strong> la de la mega-<\/span>inundaci\u00f3n<\/span><\/strong> que interrumpi\u00f3 la <\/span><\/strong>corriente termohalina<\/a>, de la que ya hablamos en un post precedente<\/a>. Y por no dejar de disparatar que no quede: \u00bfSi nos aliment\u00e1ramos de grandes herb\u00edvoros hasta casi exterminarlos durante las fases c\u00e1lidas y nos tornamos vegetarianos durante las fr\u00edas, dejando aquellos a sus \u201cflatulentos aires\u201d, podr\u00edamos regular el clima. Supongo que Felisa estar\u00eda de acuerdo. Dejando a la t\u00eda Felisa tranquila, veamos algunos puntos clave de esta controversia.<\/p>\n

\u00a0(i). Se especula mucho sobre si el hombre o el clima fueron causantes de las grandes crisis cuaternarias. Sin embargo, las interacciones clima-hombre, como se comenta en este caso, no den ser soslayables, sino todo lo contrario.<\/p>\n

\u00a0(ii) Las extinciones de los grandes mam\u00edferos, as\u00ed como de los vertebrados gigantes que les reemplazaban a aquellos en sistemas los insulares, son diacr\u00f3nicas y generalmente asociadas a la presencia de seres humanos.<\/p>\n

\u00a0(iii) Las megainundaciones causadas\u00a0 por la ruptura de presas de hielo durante la \u00faltima desglaciaci\u00f3n tampoco parecen haber sido sincr\u00f3nicas, ya que los datos de los cambios clim\u00e1ticos de que disponemos \u201cactualmente\u201d atestiguan que no se produjeron exactamente al mismo tiempo en todo el planeta.<\/p>\n

\u00a0\u00a0\"mamutus-en-arizona-fuente-northwest-coast-archaeology\"<\/p>\n

Mamuts en Arizona. Fuente: The Archeology or Arizona according to T-rat.com <\/a><\/p>\n

\u00a0(iv) No se puede especular sobre la implacable agresividad de los clovis obsesivamente antiflatulentos, por cuanto las estepas euroasi\u00e1ticas atesoraban mucha mayor extensi\u00f3n, mientras sus moradores tambi\u00e9n se alimentaban de Mamuts y otras especies de una megafauna tambi\u00e9n extinta. \u00bfSe comunicaban los humanos de entonces m\u00f3vil, o les bastaba el \u201ctan-tan\u201d?: \u00a1cargu\u00e9monos a estos hediondos bichos que apestan!. \u00a1Ok recibido, camarada Manutchof!.<\/p>\n

\u00a0(v) Resulta comprensible, que ciertos debates duren alg\u00fan tiempo, a falta de pruebas, pero cansa hasta la desesperaci\u00f3n que cada a\u00f1o, los \u201cclimat\u00f3filos\u201d y los \u201chumanodepredators\u201d se aticen al menor indicio adicional que aparezca. Pero con las predicciones de los modelos de simulaci\u00f3n num\u00e9rica (seg\u00fan las diferentes asunciones utilizadas en cada uno) tal modo de proceder deviene en exponencialmente infraccionario (\u00bfo infraccionario?). Eso s\u00ed, sus papers cuelan en las revistas de mayor impacto. \u00bfSe trata de ciencia buena?<\/p>\n

\u00a0(vi) Otra gran fuente de metano resultan ser los suelos de permafrost y turberas, cuando se deshielan<\/span><\/strong>. Empero como los zo\u00f3logos no parecen leer de vegetaci\u00f3n, ni los bot\u00e1nicos de suelos (\u2026.).\u00a0\u00a0\u00a0 \u00a0<\/p>\n

\u00a0(vii) Lo que si parece estar bastante claro<\/span><\/strong>, con las evidencias actuales, es que una gran megafauna se extingui\u00f3 asincr\u00f3nicamente desde la \u00faltima glaciaci\u00f3n<\/span><\/strong>. Si \u201casumimos\u201d (pero hay que demostrarlo) que los grandes reba\u00f1os<\/span><\/strong> metanog\u00e9nicos requieren amplios espacios abiertos<\/span><\/strong>, lo que queda en entredicho<\/strong> es asumir la presencia de bosques en muchas regiones del planeta<\/strong>, cuando posiblemente debieran atesorar estructuras sabanoides. Y tal cambio en la estructura de la vegetaci\u00f3n si acarrear\u00eda modificaciones en el clima, pero tambi\u00e9n que tanto los suelos como su ecolog\u00eda<\/strong><\/span>. Estos difieren ostensiblemente bajo bosques y coberturas herb\u00e1ceas<\/span><\/strong>. Resulta que, sobre este tema, parece investigarse menos. Sin embargo, tambi\u00e9n existen retroalimentaciones significativas suelo-clima<\/span><\/strong>. As\u00ed que\u2026\u2026\u2026 \u00bfA si que qu\u00e9, que de qu\u00e9?. En una o dos semanas, en Nature o Science, volver\u00e1n a las andadas \u00bfque fu\u00e9 antes, el huevo o la gallina? \u201conce again<\/em>\u201d. \u00bfCiencia de vanguardia?. No, simplemente ciencia especulativa alimentada medi\u00e1ticamente. Y la pregunta del mill\u00f3n: \u00bfPoque actualmente tan solo atesoramos sabanas en \u00c1frica?<\/span><\/strong><\/p>\n

\u00a0Y el octavo d\u00eda Dios trajo al mundo los grandes herb\u00edvoros, con su hediondo metano y (\u2026) el clima se calent\u00f3, comenzando a oler todo mal, muy mal. El hombre no supo entender que el divino creador nos regal\u00f3 estos enormes bichos para que \u00e9l, gestion\u00e1ndooslos, pudiera cambiar el clima a su antojo. Y seguimos sin percatarnos \u00bf?.<\/p>\n

\u00a0Lamentablemente continuar\u00e1\u2026\u2026\u2026\u2026.\u00a0 \u00a0\u00a0\u00a0\u00a0\u00a0<\/span><\/em><\/strong><\/p>\n

\u00a0Juan Jos\u00e9 Ib\u00e1\u00f1ez<\/span><\/strong><\/p>\n

\u00a0<\/p>\n

Earth Blows Hot And Cold<\/a><\/h2>\n

Terradaily<\/span><\/strong>: by Alison Hawkes\u00a0 for Hot Zone blog<\/a>: Moffett Field CA (SPX) Jun 16, 2010<\/p>\n

Around 12,000 years ago, the Earth spun into The Big Freeze, a (geologically) brief cold snap known as the Younger Dryas event<\/strong>. Glaciers returned to parts of the Northern Hemisphere and humans who <\/strong>were around then probably shivered quite a bit.<\/p>\n

The Clovis people in North American<\/strong>, the first paleo-Indian inhabitants that made distinctive bone and ivory tools<\/strong>, took a population nosedive. What caused The Big Freeze? <\/strong><\/p>\n

The prevailing theory is a shutdown of the ocean conveyor belt caused by a rapid influx of fresh water from the melting of an immense glacial lake – Lake Agassiz<\/strong> – the used to cover much of Canada. Comets are also speculated culprits. But <\/strong>a New Mexico team of researchers is looking into an unusual contributing factor – a steep decline in large animal flatulence<\/strong>.<\/p>\n

It’s no secret that humans probably caused the extinction of megafauna species in the New World, which used to be richer than modern day Africa. Within a thousand years of human arrival, species like mammoth, camelids<\/strong> (the ancestors of camels) and giant ground sloths<\/strong> were destined as museum pieces.<\/p>\n

\u00a0In a paper published in Nature Geoscience<\/strong> this month, Methane Emissions from Extinct Megafauna<\/strong>, Felisa Smith of the biology department at the University of New Mexico and colleagues, attribute a steep drop in atmosphere methane levels to the disappearance of these behemoths<\/strong>.<\/p>\n

If domestic livestock contributes about 20 percent of global methane emissions today, then mammoths and the like must have had powerful bowels. Since Pleistocene methane levels were considerably lower than today, these megaherbivores might have had a larger influence on global methane levels<\/strong>.<\/p>\n

\u00a0The researchers went about estimating how much gas an 8-ton herbivore would emit. <\/strong>They examined 114 herbivores that went extinct<\/strong> at the end of the Pleistocene epoch<\/strong>, adjusting for body size and other traits to compute overall methane production from these beasts<\/strong>.<\/p>\n

\u00a0Their calculation suggested that the Pleistocene extinction dropped methane levels by about 9.6 teragrams (or megatons), making the mass extinction responsible for somewhere between a 12.5 to 100 percent of overall methane decline<\/strong>. That’s a big range, but the researchers go on to point out a unique attribute of global methane decline at that time. It happened quite quickly, two to four times faster than any other time interval, \u00abwhich suggests that novel mechanisms may be responsible<\/strong>.\u00bb<\/p>\n

\u00a0Novel, indeed. The overall drop in methane, a potent greenhouse gas<\/strong>, during that epoch equated to temperatures 16 to 22 degrees Fahrenheit cooler. The researchers write: The attribution and magnitude of the Younger Dryas temperature shift, however, remain unclear. Nevertheless, our calculations suggest that decreased methane emissions caused by the extinction of the New World megafauna could have played a role in the Younger Dryas cooling event<\/strong>. They go on to say that the megafauna extinction may have been \u00abthe earliest catastrophic event attributed to human activities.\u00bb It may even be the first time humans altered the climate<\/strong>.<\/p>\n

\u00a0Massive wildfires that cause untold destruction of life and habitat are becoming a feature of modern climate change<\/strong>. A mere 1.8 degree jump in temperature is predicted to equal a 40 percent increase in lightening, the main ignition source of natural fires. We already get some 8 million strikes a day under modern atmospheric conditions. It’s becoming sizzling hot here on Earth.<\/p>\n

\u00a0New research into the past is backing up modern day observations. In a paper published in May in Nature Geoscience, researchers at University College Dublin and colleagues tracked down climate and fire conditions from 200 million years ago during a major environmental transition period in Earth’s history – the Triassic-Jurassic boundary. During this period, massive volcanism broke apart the super-continent of Pangaea and spiked CO2 levels from 600 to more than 2,100 parts per million by volume<\/strong>. For comparison, Earth’s current CO2 concentration is about 391 ppmv, an all time high for recent history. The resulting mass extinction gave way to our most imaginative period in paleo-history – the age of large dinosaurs. Common, too, emerged the conifers – woody plants with thin needles and seed-bearing cones<\/strong>.<\/p>\n

\u00a0What the researchers found was that as CO2 spiked, so did the number of fires. <\/strong>They looked at about 15,500 fossil charcoal particles from this time period in East Greenland and discovered a five-fold increase in charcoal abundance during peak CO2 levels<\/strong>. The vegetation also appeared to be changing. As temperatures rose, broad-leafed plants died off and were replaced by narrow-leafed varieties<\/strong>. These narrow-leafers were able to withstand higher temperatures, but were also more prone to burn because they contained less moisture. Just think of the last campfire you built – what do you throw in to really get it going? Pine needles.<\/p>\n

The researchers suspect a positive feedback loop emerged. As more lightening struck, the ignition rates and spread of wildfires increased due to the burn-prone vegetation, which then released more carbon back into the atmosphere and exacerbated the conditions even more.<\/p>\n

\u00a0What this says about modern day climate change is informative. All that fiery turmoil during the Triassic-Jurassic boundary happened with a temperature change of about 7 degrees Fahrenheit<\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"

Durante el final de la \u00faltima glaciaci\u00f3n cuaternaria se produjeron varias pulsaciones clim\u00e1ticas enormemente bruscas fri\u00f3-calor-fr\u00edo-calor, hasta entrar en el Holoceno, en donde r\u00e1pidamente surgi\u00f3 la agricultura (Neol\u00edtico). Hablamos de\u00a0 las pulsaci\u00f3nes del Dryas antiguo y reciente. Como ver\u00e9is pinchando en este \u00faltimo enlace, existen teor\u00edas para todos los gustos a la hora de explicar la raz\u00f3n de cambios clim\u00e1ticos tan abruptos. \u00a1Y como no!, ya que los mamut norteamericanos desaparecieron durante ese evento (junto con otros grandes mam\u00edferos como los cam\u00e9lidos), los climat\u00f3filos actuales vuelven la vista a las grandes emisiones de metano que deb\u00edan petar tales enormes bestias\u2026<\/p>\n","protected":false},"author":26,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"ngg_post_thumbnail":0},"categories":[603,618,607,595],"tags":[2050,2049,2051,2052],"blocksy_meta":{"styles_descriptor":{"styles":{"desktop":"","tablet":"","mobile":""},"google_fonts":[],"version":4}},"aioseo_notices":[],"_links":{"self":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136675"}],"collection":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/users\/26"}],"replies":[{"embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/comments?post=136675"}],"version-history":[{"count":8,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136675\/revisions"}],"predecessor-version":[{"id":136933,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/posts\/136675\/revisions\/136933"}],"wp:attachment":[{"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/media?parent=136675"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/categories?post=136675"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.madrimasd.org\/blogs\/universo\/wp-json\/wp\/v2\/tags?post=136675"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}