Friday, August 8, 2014

My Fun Evolution Trip Part 1: Ashfall Beds, Nebraska

Today I begin a series of essays about a long trip I recently completed, which took me from Oklahoma to Idaho and back, stopping at lots of places of ecological and evolutionary interest. The second day of the trip, July 20, I visited Ashfall Beds in Nebraska, which is one of the most amazing fossil deposits in the world.

Ashfall Beds State Park is in rural Nebraska. It is not on the way to anything, but it was my principal reason for going to Nebraska. But it is well worth a trip to Nebraska even if for no other reason.

About twelve million years ago, life was abundant in the savannas of what is now Nebraska. There was certainly an abundance of animal life. Reptiles included the giant Hesperotestudo tortoise, now extinct. Among the now extinct mammals were horned rodents of the family Mylagauidae, the “raccoon dog” Cynarctus, saber-toothed deer (I am not making this up), and three-horned deer. There was a kind of dog that specialized on eating fruit. There were three kinds of small camels. The most abundant mammal in this fossil deposit was the now extinct rhinoceros Teleoceras.

The nearest relatives of some of these mammals live today in Eurasia and South America. Mammals such as these and many others were thriving in North America until about twelve thousand years ago (not twelve million), when they died in the Pleistocene Extinction. This extinction event probably resulted from the interaction of climate change and overhunting by newly-arrived humans, neither one of which by itself would have been sufficient. It was an interaction, with the effects of climate change amplifying the effects of overhunting, and not a simple additive effect.

What was perhaps most interesting about these mammals is that they represented earlier stages of evolution. The best example is probably the horses. Some of them, such as Protohippus and Hypohippus, had three toes, while others, like Pliohippus and Hipparion, had a hoof and two small stubby toes. Some horses grazed (ate grass), while others browsed (ate broad leaves). The specimen numbered "2" is one of the horses.

What happened? One day a volcano over the Yellowstone Hot Spot erupted and sent ash into the air. The finest ash traveled to what is now Nebraska, where it covered the leaves and grass. The mammals breathed and ate the ash. Tubercles on their bones showed that they survived for weeks (but not years) after eating the ash. One of the symptoms was that they got very thirsty and converged on a water hole. But drinking water did not save them, and they died, piled up on top of one another at the water hole. That’s where we find the mass of bones today, entombed in volcanic ash. It was not like one day in Pompeii; it took a few weeks, but with the same effect.

Creationists have a nearly impossible time explaining such a fossil deposit. They make no attempt at all to explain how Noah’s Flood could have produced this deposit. Instead, they claim that this deposit was formed after the flood in pretty much the way scientists have discovered. They just claim that it all happened in the last four thousand years rather than the twelve million years indicated by radiometric dating of the ash. Processes such as the formation of the sedimentary cap over the volcanic ash occur slowly today, but the creationists simply invoke a more rapid pace, perhaps of miraculous origin. The Bible indicates no such miracles, but creationists love to just make up miracles whenever they want to. In one creationist article about Ashfall beds, the authors do not address why the mammals are similar to but not the same as modern mammals—for example, the three-toed horses. There were no modern horses of the genus Equus. And no modern camels (even the South American ones) or dogs or cats or… Are we to suppose that God scooched the primitive-looking mammals over to North America, and kept the modern ones out, just to trick us into accepting evolutionary science?

Ashfall Beds is an amazing place to see fossils which fit in perfectly with evolutionary processes and the evolutionary timeline.

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