Topping noticed that the erroneously low ages seemed to cluster for Clovis sites from the Great Lakes region and Canada, whereas more southerly locations gave ages closer to the age of the Clovis disappearance as known from other evidence. He decided to visit the site at Gainey, Michigan, which was close by and where C-14 dates were as low as a few hundred years, even though Clovis was known to be about 13,000 years old.
Topping studied flakes of chert from Gainey under high magnification and saw microscopic pits with raised rims like miniature meteorite impact craters. He soon found the microcraters at two other Clovis sites. At the bottoms of many of the pits lay what appeared to be minuscule balls of iron.
Reasoning that he might find more of the micro-balls disaggregated in the sediment than still locked up in the chert, Topping collected samples of the peculiar yellow dust that marks the Gainey site. He found that a powerful magnet allowed him to extract the particles from the dust. They turned out to be perfectly spherical and to occur in much greater abundance at the Clovis level than above or below it. These microspherules, as they became known, were fifty times smaller than a human hair and present in the tens of thousands.
MAMMOTH TRUMPET
Richard Firestone, working at the Lawrence Berkeley National Laboratory, learned of these preliminary findings and became so intrigued that he joined in the quest to solve the Clovis mystery. Firestone and Topping studied eleven Clovis sites, most of which had anomalously young C-14 ages. At many they found the micropits, microspherules, and other evidence that they interpreted as extraterrestrial. In 2001, the two published an article on their findings in an informal magazine called Mammoth Trumpet. The title of their article was “Terrestrial Evidence of a Nuclear Catastrophe in Paleoindian Times.” They posited that the source of the added radiocarbon was a supernova, an exploding star that had spread matter and subatomic particles throughout a large region of space. The resulting nuclear irradiation would have converted more nitrogen-14 atoms in Clovis-age charcoal to radiocarbon, making them appear younger and explaining the radiocarbon discrepancy at the YD, the original purpose of Topping’s work. A supernova around the time of the YD was not a wild idea, but a scientific one that Robert Brakenridge of the University of Arizona had proposed in a peer-reviewed article titled, “Terrestrial Paleoenvironmental Effects of a Late Quaternary-Age Supernova.”
But to get the idea of a cosmic event at the YD before a scientific audience would require more than a book like The Cycle or an article in Mammoth Trumpet. It would require publication in a peer-reviewed scientific journal.
2
THE YOUNGER DRYAS IMPACT HYPOTHESIS
Firestone and colleagues first presented their hypothesis in a talk at the May 2007 meeting of the American Geophysical Union. In October 2007, they published it in Proceedings of the National Academy of Sciences under the title: “Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling.” It was long, detailed, and carefully laid out the evidence for the Younger Dryas Impact Hypothesis.
In its scientific influence and prestige, the Proceedings of the National Academy of Sciences ranks just behind Nature and Science. The authors included a member of the National Academy of Sciences and well-published scientists from more than a dozen research universities. They represented a range of specialties and included some who were YD experts. This should have assured that the hypothesis would get a fair hearing from the scientific community at large, and at first, it did.
FEA now reported that new evidence had led them to abandon the supernova burst of The Cycle and instead to propose that a comet had exploded over North America, destabilizing the great Laurentide Ice Sheet that covered most of northeastern North America and triggering the YD cooling. The authors chose a comet because unlike an asteroid, these balls of dirty ice often explode in the air and fail to leave a telltale crater behind, thus explaining the absence of one of YD age.
MURRAY SPRINGS AND THE BLACK MAT
The article focused on the analysis of samples collected by Allen West from several YD sites. One was at Murray Springs, Arizona, SE of Tucson, the first that West visited. There he met Vance Haynes, Professor Emeritus at the University of Arizona, who had discovered the site in 1966 and become a leading expert on Clovis archeology and one of the most respected archeologists. Haynes pointed his rock hammer at a thin, black layer exposed in the side of a gulley at Murray Springs and said to West, “That’s the black mat. We’ve found it at dozens of places. Always, we find the Clovis artifacts and extinct animal bones right under it.”
FIGURE 1:
Vance Haynes (L) and Allen West at Murray Springs, observing the Black Mat.
Haynes had published extensively on the mat, which scientists have found not just in southern Arizona but, as Haynes put it: “from nearly the Atlantic to the Pacific,” and even in Canada and Mexico. The mat had long puzzled Haynes, but he was still unsure what caused it.
The black mat has several distinctive characteristics. It is:
1. Thin and therefore was deposited in a relatively brief period of time.
2. Of the same age as the YD onset at each well-dated Clovis site.
3. Found on a continental scale.
4. Evidently somehow connected to the cause of the YD itself.
This set of features is rare and hard to explain by normal geologic processes. One that matches it is the Cretaceous-Tertiary (KT) boundary clay. The airburst or impact of an ET object would have been instantaneous and had simultaneous and widespread effects. So might a continental-scale volcanic eruption. But YD sites show no sign of volcanism and as we will see, the evidence from the Greenland ice cores and elsewhere rules it out at the Younger Dryas boundary (henceforth, YDB). Thus by itself, the black mat suggests that something unusual happened at the YDB and that something could have been an extraterrestrial event.
Haynes went on to tell West:
No skeleton of extinct megafauna has ever been found in or above the black mat, only below it, and no Clovis artifact has ever been found in or above the mat either. The American horse, dire wolf, sabertoothed tiger, American camel, mammoth, and mastodon, all of them disappeared in an instant before the black mat formed. When we dig up their bones today, the black mat covers them like a blanket.
The lack of megafaunal remains above the YD reminds us of the absence of dinosaur fossils “in place” (rather than having been eroded and re-deposited in younger rocks) above the KT boundary clay. Such absences suggest the occurrence of a virtually instantaneous and extensive event extreme enough to cause, in the case of the YD, the extinction of dozens of megafaunal species and possibly the disappearance of the Clovis culture, and in the case of the KT, two-thirds of all living species.
The widespread presence of the black mat thus was consistent with an anomalous and possibly extraterrestrial event at YD time, but to persuade scientists to consider the YDIH would require positive and familiar evidence of impact. By the time FEA wrote, the criteria for recognizing ET events from the geologic evidence were well established. It was against these criteria that the YDIH would be tested.
FEA collected samples above, in, and below the YDB at ten Clovis sites. One was at Blackwater Draw near Clovis, NM, which is the type-site for Clovis projectile points. The one at Gainey, MI, which Topping visited, is the type-site for a similar Clovis-style point. Three of the ten are megafaunal kill sites and six have the black mat directly over the YDB. One site is at Lommel in northern Belgium. This was a good sampling across a wide range of YDB sites.
In the YD boundary layer itself, directly below the black mat, FEA found not only the microscopic magnetic grains and microspherules that Topping had found at Gainey, but also glassy carbon containing diamonds one-billionth of a meter in size, elevated amounts of iridium, and evidence of wildfire in the presence of charcoal and soot.
FEA presented the results for six of the sites in charts showing a vertical profile through the YDB. As an example, let us
use their section for Murray Springs.
Figure 2:
Event markers peak at the YDB at Murray Springs from Firestone at al. (2007). See text.
The center frame is a photograph of a vertical section through the YDB at Murray Springs. The view extends from 20 cm below the boundary to 40 cm above it, a span of 60 cm or about two feet. The black mat stands out dramatically. If we judge the width of the YDB layer itself from the width of the base of the peaks, it looks to be about 5-6 cm, or 2-2.5 inches, roughly the width of three fingers. In the brief span of time represented by that thin layer, the Earth began to cool and something happened to the megafauna and the Clovis culture that prevented their remains from ever appearing above it. Whatever that something was, it happened on the scale of thousands of miles. As the chart also shows, it occurred 12,990 ± 130 years ago. (Later scientists would improve the accuracy and precision (±) of the age of the YD and also test whether the YDB is the same age everywhere, a key criterion of an extraterrestrial event.)
The chart shows how at Murray Springs the number of what FEA called “event markers” are scarce or absent below and above the YDB, but peak right at it. The other sites show similar peaks, though they vary somewhat by site. How can we explain the peaks?
First we would have to recognize that microspherules and magnetic grains are present on Earth, for example in fly ash produced by industrial processes. So the mere presence of these objects at YDB sites does not automatically connote an ET origin. But they are not randomly distributed around the YDB, instead rising to easily recognized peaks coincident with it. In trying to assess the YDIH, the presence of these peaks represents the single most critical piece of evidence and we will spend a whole chapter on them. For now, let ask whether such peaks could have arisen from terrestrial processes.
The event markers could not derive from modern industry because they are 13,000 years old. But still, normal geologic processes could have produced them. Are there any such that would work? One general possibility is erosion, which could wash away soluble and easily transported material, leaving the rest behind to accumulate in the residual layer. But the ten sites that FEA studied included deposits from a coastal canyon, arid-region streambeds, caves, lake and pond deposits, as well as glacial moraines and drumlins. The composition of the sediment at the boundary ranged from a dense clay to a gravelly sand. It is hard to see how a terrestrial process could work with this range of environments and compositions to produce identical event marker peaks over such a wide range.
Another possibility is the opposite of erosion. Suppose that there had been a slow-down in the rate of deposition at YD time, allowing the ET material that is constantly sifting down to Earth to accumulate anomalously. But Haynes had written that the level representing the YDB had lasted less than a decade, far too short a time for this possibility to work. Also, given the widespread range of the sites that FEA investigated, the slow-down in deposition would have to have occurred on a hemispheric scale, and for that there is no evidence.
Thus it is very hard to come up with a way to explain the YDB event marker peaks by anything other than an ET event. But there was one way out. We will come to it in Chapter 5.
The FEA article ends on a cautious note, not claiming confirmation of the YDIH but saying rather that “Our primary aim is to present evidence” for it. The authors invite other scientists to test that evidence and conclusions, saying that “These associations, if confirmed, offer the most complete and recent geological record for an ET impact and its effects, such as global climate change and faunal extinction.” Unlike the KT, “This evidence also would represent a record of a major ET event having serious, widespread consequences for anatomically modern humans.”
But how do scientists go about confirming the evidence and conclusions presented by their peers? The answer would become the crux of the fate of the YDIH.
3
TESTING HYPOTHESES
According to the standard view of the “scientific method,” scientists come up with a hypothesis, predict what they should find if it is true, then devise experiments to test those predictions. If enough predictions are met, a hypothesis can be promoted to the status of theory. Practitioners work under it until a better theory comes along and the paradigm shifts.
In the earth and historical sciences, which deal with past events, it is rare to be able to test a hypothesis in the laboratory or from current, real-time observations. Instead, Nature (or in archeology and anthropology, our distant ancestors), in a sense conducted the experiments and, we hope, left clues for scientists to find. They may not find those clues, or if they do, may be unable to interpret them with the present state of knowledge. When scientists simply fail to find evidence, they confront the oft-cited dilemma that, “absence of evidence is not evidence of absence.” In other words, just because a scientist finds no evidence does not mean that none exists. The evidence might be inherently scarce, as it was with dinosaur fossils, and with the human bones that provide the archeological record, such as those of Lucy.
Philosopher Karl Popper introduced the idea that a scientific theory can never be proven true, only falsified. No matter how strong a theory may be, new evidence can always turn up to weaken and eventually falsify it. Popper’s proposition became controversial and we will not settle the matter on these pages. Suffice it to turn to common sense and note that to be useful, a theory must make predictions that scientists can test. An idea that makes no predictions does not offer scientists anything to do.
In practice, a single failed prediction or contrary finding is usually not enough to falsify a well-established theory. Instead, scientists first try to modify the theory so as to accommodate the new finding and often they succeed. If there are enough such unexplained discrepancies, scientists move on to a more promising theory, usually with no grand announcement but just by voting with their feet.
The Alvarez Theory of dinosaur extinction predicted many things, but the most important may have been that the impact and the extinction both occurred at exactly the same moment of geologic time. Scientists confirmed the simultaneity in 2013, but even that was not enough to change the minds of some career-long, likely to be life-long, opponents of the theory. As we will see, a similar test came to be applied to the YDIH.
PREMATURITY
When scientists do allow a single finding to cause them to reject a hypothesis or theory, they often turn out to have acted prematurely and made a mistake. The “CO2 Theory” is a good example.
In 1896, Swedish scientist Svante Arrhenius published the results of laborious hand calculations — said to be more than 10,000 — to show that changes in the amount of CO2 in the atmosphere could explain ice-age temperature variations. At first, his theory was well received, then came an experiment that seemed to show that the atmosphere is “saturated” with CO2, so that adding more would not cause additional warming. This interpretation was false, but those who opposed the CO2 theory never questioned it, announcing with relish that same year that the theory “evidently fails.” For the next 50 years, this hasty interpretation gave early meteorologists an excuse to ignore the role of CO2 in climate, quite likely costing lives in the not-so-distant future.
Many rejected Alfred Wegener’s theory of continental drift before they had even read what he wrote about it, believing that it violated uniformitarianism and that in any case it is impossible for continents to plow through the Earth’s rigid interior. (His Origins of Continents and Oceans was not translated into English until 1924.) Others cited the “lack of a mechanism” that could explain why the continents moved, allowing them to ignore the evidence that they had moved. One wise geologist responded, “Whatever has happened, can.”
YDIH PREDICTIONS
The YDIH starts with the assertion that an extraterrestrial event occurred at the onset of the YD cooling. Whether such an event happened is the first major question we will take up in this book. If the answer is no, then of course a non-event can have no consequences. But if there is
a preponderance of evidence that the ET event did occur, then we can ask a second set of questions: whether it triggered, or at least contributed to, the YD cooling, the megafaunal extinction, and the waning of the Clovis culture.
If an extraterrestrial event launched the YD, what would we predict?
Prediction 1: The YDB will have the same age everywhere.
Extraterrestrial objects travel at hypersonic speeds of tens of thousands of miles per hour. Since the kinetic energy of a moving object rises with its velocity squared, their speed gives even small cosmic bodies tremendous energy and destructive power. The dinosaur killer is estimated to have had the energy of 100 million tons of TNT. Compare that to the energy of the bomb that destroyed Hiroshima: about 15,000 tons.
When ET objects strike the earth or burst in the atmosphere, the event is instantaneous and the ejecta is thrown widely to settle out in days or weeks, making the deposits the same geologic age wherever they occur.
Conversely, if the YDB was to have significantly different ages at different places, then they could not have been caused by an instantaneous event. Thus, if this prediction were to fail, the YDIH would have been falsified without the need to consider any other evidence. That is why I list it first.
Prediction 2: The composition and features of the event markers will allow them to be distinguished as extraterrestrial rather than terrestrial.
As we noted, microspherules, for example, can form in several different ways due to both cosmic and terrestrial causes. But only one type would bear the distinctive features of an ET event and corroborate the YDIH. But to detect those diagnostic features takes more than inspecting them under a high-powered optical microscope: it requires special techniques such as scanning electron microscopy (SEM) and X-ray spectrometry (XRS).
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