More Evidence against the Climate Change Model of Late Pleistocene Extinctions

Many extinct species of Pleistocene megafauna had a wide ranging geographic distribution.  Jefferson’s ground sloth, long-nosed peccary, Columbian mammoth, and mastodon occurred from coast to coast and from Florida to the glacial boundary.  These species and their similar evolutionary ancestors existed across the continent for millions of years, surviving dozens of major and minor climatic fluctuations.  They lived in a variety of environments and were capable of subsisting on many different foods.  Multiple lines of evidence show these pre-historic beasts ate a varied diet.  Mastodon coprolites (subfossil feces) contain bald cypress, buttonbush, spruce twigs, fruit, acorns, aquatic plants, and numerous other items.  Now, a new study of mastodon teeth using dental microwear texture analysis confirms that mastodons ate a wide variety of foods.

Mastodon tooth.  Scientists looked at mastodon teeth using microscope technology and determined mastodons from different regions ate different foods.

Scientists microscopically examined 65 mastodon teeth that were found in 4 different geographic locations including Florida, Missouri, Indiana, and New York.  The microwear found on mastodon teeth from Florida differed from wear on teeth from northern mastodons.  Florida mastodons primarily ate bald cypress twigs, while northern mastodons ate spruce, hemlock, pine, larch, and juniper.  The differences in tooth wear indicate mastodons could eat a variety of plant foods and were not dependent upon a single species.  The authors of this study also looked at mastodon teeth from different climatic stages in Missouri.  Mastodon teeth from a climate stage when open jack pine and prairie predominated showed little difference from teeth dated to a climate stage when spruce dominated the landscape.  The microwear on mastodon teeth resembles the microwear found on 2 living species–moose and black rhino.  Like mastodon, these 2 species subsist on woody browse.

I think this study is just more evidence against the climate change model of extinction that proposes changes in climate caused corresponding changes in plant composition, leading to megafaunal extinctions through nutritional deficit starvation.  None of the plants mastodons ate ever disappeared or even became rare in the environment. The authors of this study take a more neutral stance toward the debate.  They acknowledge the “plasticity” of mastodon diet but seem reluctant to admit their study is strong evidence against the climate change model of extinction.  Instead, they suggest future studies using dental microwear texture analysis could uncover the reason why megafauna became extinct.  In my opinion it already has.  Their data rules out the climate change model of extinction by revealing the dietary adaptability of mastodons.  Through the process of elimination, human overkill is the only plausible cause left standing.

Reference:

Green, J.; Larisa DeSantis and G. Smith

“Regional Variation in the Browsing Diet of Pleistocene Mammut americanum (Mammalia, Proboscidea) as Recorded by Dental Microwear Texture Analysis”

Paleogeography, Paleoclimatology, and Paleoecology August 2017

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Tags: Dental Microwear Textural Analysis, mastodon teeth