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Dr. Mike Voorhies is a vertebrate paleontologist who studies the evolution of later-Cenozoic mammals and the stratigraphy of the rocks in which they are found. As a 20-year-old paleontology student in 1962, he helped excavate the fossil skeletons of the two mammoths discovered locked together by their tusks (and profiled on NOVA scienceNOW). Voorhies went on to get his doctorate at the University of Wyoming in 1966. Then, in 1971, while walking on a ranch with his wife, he stumbled upon the skull of an extinct rhinoceros calf eroding out of a ravine; it turned out to be a complete skeleton preserved in volcanic ash. Since then, dozens of other fossil skeletons have come out of what is now the Ashfall Fossil Beds State Historical Park in Royal, Nebraska, where Voorhies spends much of his time. Since 1975, he has taught geology and paleontology at the University of Nebraska in Lincoln (UNL) and been Curator at the State Museum. Now an emeritus professor at UNL, Voorhies continues his special interest in excavating mass bonebeds in the Great Plains, including the Ashfall Fossil Beds, and interpreting how they formed (taphonomy). |
On August 5, 2008, Mike Voorhies answered selected viewer questions about the pair of mammoths found locked together by their tusks, about Ice Age extinctions, about his particularly early start in paleontology, and more. Please note we are no longer accepting questions, but see A Mammoth Waste of Time and our Links & Books section for more information. Q: The show didn't mention where these fossils are now. Are they visible to the public? A: Yes, the two interlocked mammoths are now on permanent public display at Trailside Museum at Fort Robinson State Park in northwestern Nebraska, only a few miles from where the skeletons were collected. The museum, a branch of the University of Nebraska State Museum (my home base), also features other locally collected fossil treasures and is well worth visiting if you are travelling west on U.S. Highway 20. Fort Robinson is only about 50 miles south of another spectacular public display, the Hot Springs (South Dakota) Mammoth Site, which features dozens of young male mammoths trapped in an Ice Age sinkhole. Q: How was the age of the bones determined (how long ago)? A: A preliminary date of 12,000 years before present was obtained on one of the mammoth bones in the 1960s. A new date using a more refined technique (accelerated mass spectrometer method) is in progress. Q: Was the mammoths' extinction due to the arrival of humans to North America? Q: What impact did human activity have on the mammoth? Q: Did the early Pleistocene man drive the mammoths to extinction by hunting them? Or did mammoths die out due to natural selection? Thank you. A: The role that humans played in the extinction of mammoths is a hotly debated topic, and no one can claim that the mystery has been solved yet. Many facts are clear: Mammoths (along with all mastodons, ground sloths, native American camels and horses, sabercats, dire wolves, giant short-faced bears... the list goes on and includes more than 40 species of large mammals) disappeared from the American fossil record within a period of less than a thousand years beginning about 11,000 years ago according to radiocarbon dates. We also know for sure that people were present in North America at least by 12,000 years ago and perhaps a few thousand years before then. Humans were definitely not present in America during most of the time (more than a million years in most cases) that mammoths and other now-extinct "megafauna" lived in North America. One theory, the "Overkill" Model, relates these facts and blames people for wiping out the big beasts. (My colleague Dan Fisher, whom you saw on the NOVA programm, has collected conclusive evidence that humans did butcher mastodons in Michigan soon before their extinction and butchered mammoth skeletons are widespread across North America.) But wait! There's another theory with many supporters—the Climate Change Model, which blames extinction on ecological change. Abundant evidence exists that climate was changing—glaciers were retreating rapidly and vegetation was changing on a large scale exactly at the same time mammoths were wiped out. Perhaps their food plants disappeared and they died of starvation? Those who support the Climate Model have a hard time swallowing the proposition that small(?) bands of roving hunters could exterminate vast herds of big game animals. My own personal guess is that neither cause by itself would be sufficient but that both together could do the job. I agree with the "Climate" people that healthy herds could not be decimated by people with stone tools. However, I think there is a basic flaw in the Climate Model, namely the fact that mammoths and other Ice Age animals had already survived dozens of advances and retreats of glacial ice across North America. I know of no evidence that points to anything unusual about the deglaciation that occurred 11,000 years ago except that people were present for the first time. My guess is that if people had arrived earlier, when the mammoths were not climatically stressed, they wouldn't have had such a severe impact. It may have been just bad luck that skilled hunters happened to come to mammoth land at exactly the wrong time. Also, remember that American animals had never seen two-legged predators and probably had no innate fear of them. They may have been particularly vulnerable to overhunting. But stay tuned—the debate is not over. A group of researchers has recently discovered a thin layer of asteroid dust dating to the time of extinction and have raised the interesting possibility that the impact of an extraterrestrial object with the Earth may have brought down the mighty mammoth, just as allegedly happened to those ever-popular hypertrophic brainless lizards, the dinosaurs! Q: Hi Dr. Voorhies! Has all study of these two entwined mammoths finished? Or are researchers still trying to answer certain questions about them? If so, what questions? Thanks. A: Work still continues on the locked mammoths. More refined radiocarbon dating is proceeding, and Dan Fisher is continuing to probe the tusks for additional clues. Q: I found the article on mammoth dung on the NOVA Web page fascinating. The reason that dung was preserved was that it was frozen (it was a woolly mammoth that lived in the Siberian arctic). Has any dung ever been found from a Columbian mammoth, like those in the show? If so, how did it preserve, and how did it compare to the Siberian dung? A: In addition to the frozen stomach contents of woolly mammoths, well-preserved dried dung of the Columbian mammoth, the species we have in Nebraska, has been obtained from a dry cave in Utah, Bechan Cave. The plants in the dung are well-preserved and were identified by scientists at the University of Arizona. The mammoths had been eating mostly grass but also a variety of herbaceous plants (dozens of species, most of which still grow near the cave today). These studies confirm that mammoths were primarily grazers that lived in open country. Their skeletons and teeth seem admirably adapted to this lifestyle. Q: Dear Sir: Are there any other cases of fossil skeletons found together in which it is clear that the prehistoric or extinct animals to which they belong died together in the midst of combat? On the one hand, it seems so unlikely given the rarity of fossilization, right? But on the other, why not, considering how sudden disasters like volcanic eruptions and landslides can bury whole landscapes in an instant. Your thoughts? Thanks. A: The only other case I'm aware of in which two fossil skeletons were discovered locked in combat is two small dinosaur skeletons found by a Polish expedition to the Gobi Desert (in the 1970s, I think). A Velociraptor and a Protoceratops apparently were struggling when they died, possibly as the result of a rapid sandslide. Although not evidence of ancient hostility, there is another example of intertwined fossil skeletons you might be interested in. It's on display at Ashfall Fossil Beds State Park here in Nebraska, where I am writing this. A female three-toed horse (Neohipparion affine) has the skeleton of a colt of the same species (almost certainly her own offspring) sheltered between her legs. These two skeletons are part of a mass-death assemblage of 12 million-year-old animals killed and buried by volcanic ash. My colleagues and I are continuing to excavate this fascinating site, which is open to the public from May through September each year. Q: Living in these environmental conditions, why was it not possible for the mammoths to seasonally migrate? A: Paleontologists suspect that some populations of mammoths did migrate seasonally, just as some African elephant populations do today. Scientific proof of migration is not easy to come by, but studies of isotopes of chemical elements preserved in fossil bones have recently proved that some extinct elephants lived in different areas at different times of the year. The case I'm most familiar with involves Florida mastodons, whose bones included strontium isotopes they could have acquired only in northern Georgia where there is lots of granite. Migration is obviously a useful survival strategy if you are mobile enough, but it obviously didn't save our native American elephants from ultimate extinction! Q: Hi! In working on mammoths and other extinct Ice Age animals, do you ever wish you could just hop in a time machine and fly back and see them, alive and well in the environment? (Or maybe my question should be: do you ever stop wishing for that!) I would think there'd be a certain amount of frustration in being so close to them in your mind—and even, geologically speaking, in time—and yet so far. A: I'm sure all paleontologists occasionally long for that mythical time machine. Personally, I don't spend much time musing about an H.G. Wells contraption when I've got a perfectly good substitute—a trowel—in my back pocket. That's the only time machine I really need to feed my intellect and imagination! Q: Hello Dr. Mike, I read in your biography on the NOVA Web site that you helped dig up the two mammoths when you were 20. What was that like at such a young age? Is that what made you become a paleontologist full-time, I mean for your career? Thank you! A: Strangely enough, I was already committed to studying paleontology when our crew excavated the entangled mammoths. I was lucky enough to get hired as a museum assistant as a 17-year-old freshman at the University of Nebraska and by the ripe age of 20, I already had three field seasons as a fossil collector behind me. I've been extremely fortunate to be able to work with fossils for my whole professional life; they are a never-ending source of wonder and joy. Thanks for your question. |
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