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| A world without Crocodilia | |
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| Topic Started: Jul 31 2017, 11:51 AM (1,292 Views) | |
| kusanagi | Aug 2 2017, 10:40 AM Post #46 |
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Adolescent
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Often these things are, the problems are when 1) non-concensus like simplistic notions of overkill are presented as near-certainties in pop sci media, and 2) when things do become a kind of scientific concensus not through presence of data but repetition in its absence (as in multiregional and Out of Africa theories, or ground up versus trees down models of bird flight, debates where both sides were killed off by increases in data). Historical narratives including palaeolontological and geological ones are prone to the latter cultural phenomena, even among actual researchers. Narrative theories exist in the absence of evidence, the actual science is built grassroots and comes piecemeal after which old narratives feel silly. And this is whats happening with models of end-Pleistocene extinctions as assumptions behind overkill are checked and new data comes to light or old data is rechecked. Though I do find it disturbing how much about living hunter gatherers was ignored or rather generalised away for decades to fit the overkill model, and where it was most popular in the USA it does fit the national history and self-image (drastic changes wrought by colonisation) as well as certain political agendas very well (environmentalism, exoneration of the worst sides of Western uniqueness). Like the other question about Pleistocene America - it's settlement, it takes on political tones easily because it touches on the national self-image. I do think its no mystery climate change was the catalyst as outside Africa vulnerability mostly follows a pattern of risk known throughout the Plio-Pleistocene. The problems are why the megafaunal part of the ecosystem didn't recover at all in the Holocene interglacial and also exactly why Africa and warm Asia were not hit. And of course questions of exactly how much impact human arrival had, and it must have had some as must the arrival of Pleistocene dogs, remain open without a globally consistent answer as regards overkill or second order predation for reasons of anthropological diversity. Whilst I'm going to refrain from saying was caused by firesticks the intensification of such land management did make the Holocene globally more different from other interglacials. Land management by fire was part of the common cultural package of modern man, so an important caveat to make here is that ecosystems and organisms must have been adapted somewhat to fire regimes by the end of the Pleistocene on all inhabited continents. But I cannot think what else there is special and global about the Holocene. Edited by kusanagi, Aug 2 2017, 03:11 PM.
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| kusanagi | Aug 15 2017, 07:10 AM Post #47 |
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Adolescent
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Mmm. Why are crocodiles not present in truly temperate habitats if other ectothermic reptiles are present? Is it competitive exclusion from 5m silurids? If oviparous turtles can inhabit Canada I can think of no reason the crocodilians could not, but Koolasuchus and champsosaurs have both been interpreted in the past as thriving where crocs were unable to live. Alligators are cold adapted to a degree yet Mississippi gators thrive best in the tropical Everglades, and the Chinese species reduced its range with Holocene climate change. This is actually something I never heard explained properly, only stated as matter-of-fact. |
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7:50 PM Jul 10