From TERRESTRIAL EVIDENCE OF A NUCLEAR CATASTROPHE IN PALEOINDIAN TIMES :
The Paleoindian occupation of North America, theoretically the point of entry of the first people to the Americas, is traditionally assumed to have occurred within a short time span beginning at about 12,000 yr B.P. This is inconsistent with much older South American dates of around 32,000 yr B.P. and the similarity of the Paleoindian toolkit to Mousterian traditions that disappeared about 30,000 years ago. A pattern of unusually young radiocarbon dates in the Northeast has been noted by Bonnichsen and Will. Our research indicates that the entire Great Lakes region (and beyond) was subjected to particle bombardment and a catastrophic nuclear irradiation that produced secondary thermal neutrons from cosmic ray interactions. The neutrons produced unusually large quantities of 239 Pu and substantially altered the natural uranium abundance ratios ( 235 U/238 U) in artifacts and in other exposed materials including cherts, sediments, and the entire landscape. These neutrons necessarily transmuted residual nitrogen ( 14 N) in the dated charcoals to radiocarbon, thus explaining anomalous dates.The theory is that something rather nasty and radiological happened about 12,500 years ago, and that's the reason the paleo-Indian artefacts appear so "young".
If a large cosmic-ray bombardment impacted the earth and irradiated the prehistoric landscape with thermal neutrons, the 235 U/238 U ratio would be changed; 239 Pu would be produced from neutron capture on 238 U, followed by the decay of 239 U. Neutrons colliding with nitrogen (1.83 barns) would create 14 C in exactly the same way 14 C is normally produced in the upper atmosphere, necessarily resetting the radiocarbon dates of any organic materials lying near the surface on the North American prehistoric landscape—including charcoals at Paleoindian sites—to younger values. 239 Pu produced during the bombardment will also be partly destroyed by thermal neutrons with 1017 barn cross section. Assuming 239 Pu doesn’t mobilize, it will decay back to 235 U (half-life 24,110 yr), partially restoring the normal abundance.Emphasis on the "Depleted Uranium" bit is in the original. A high incidenmce of Depleted Uranium means things have been irradiated, simple as that. One way that the anomalous dates could be explained would be if the whole of the Great Lakes region had been hit by "thermal" neutrons. Slow moving ones. The most dangerous kind. A lot of them. How bad would it have been (and how bad would it be if it happened again?)
Paleoindian artifacts from Gainey, Leavitt, and Butler, and two later-period artifacts from the same geographic area of Michigan were analyzed for 235 U content by gamma-ray counting at the Phoenix Memorial Laboratory, University of Michigan. They were compared with identical chert types representative of the source materials for the artifacts. Control samples were extracted from the inner core of the purest chert known to be utilized by prehistoric people. The Paleoindian artifacts contained about 78 percent as much 235 U as the controls and later-period artifacts, suggesting substantial depletion. Depletion of 235 U necessarily indicates that thermal neutrons impacted these artifacts and the surrounding prehistoric landscape.
The Paleoindian catastrophe was large by standards of all suspected cosmic occurrences. Normal geomagnetic conditions would focus cosmic rays towards the magnetic poles, concentrating their severity in those regions. However, low magnetic field intensity during a geomagnetic excursion may have allowed excessive cosmic rays to strike northeastern North America. (Whether the geomagnetic excursion admitted cosmic radiation, or the radiation caused the excursion, is uncertain. Given our present state of knowledge, cause and effect in this instance are unclear.) The presence of a nearby small and dense interstellar cloud may explain the origin of the particle bombardment. The size of the initial catastrophe may be too large for a solar flare, but a sufficiently powerful nearby supernova or cosmic ray jet could account for it. It appears that the catastrophe initiated a sequence of events that may have included solar flares, impacts, and secondary cosmic ray bombardments.Oops. This doesn't sound good...
The enormous energy released by the catastrophe at 12,500 yr B.P. could have heated the atmosphere to over 1000C over Michigan, and the neutron flux at more northern locations would have melted considerable glacial ice. Radiation effects on plants and animals exposed to the cosmic rays would have been lethal, comparable to being irradiated in a 5-megawatt reactor more than 100 seconds.Ah. Oh-Kay. That's pretty Bad. About the same as a million multi-megaton Neutron bombs being let off in the upper atmosphere. Yes, that's pretty bad alright. SPF factor 1 million sunscreen wouldn't help, it's the thermal neutrons that would be the real killer, the temperatures hot enough to melt steel and glass would just be the icing on the cake.
The overall pattern of the catastrophe matches the pattern of mass extinction before Holocene times. The Western Hemisphere was more affected than the Eastern, North America more than South America, and eastern North America more than western North America. Extinction in the Great Lakes area was more rapid and pronounced than elsewhere. Larger animals were more affected than smaller ones, a pattern that conforms to the expectation that radiation exposure affects large bodies more than smaller ones. Sharp fluctuations of 14 C in the Icelandic marine sediments at each geomagnetic excursion are interesting; because global carbon deposits in the ocean sediments at a rate of only about 0.0005 percent a year, a sudden increase in sediment 14 C may reflect the rapid die-off of organisms that incorporated radiocarbon shortly after bombardment.So the plants and wildlife in North America are basically mutants who survived something far worse than the greatest Global Thermonuclear War ever conceived. And the native peoples are those who migrated to the newly emptied land afterwards, and re-colonised it. Of course, the impact of such a catastrophe wouldn't be confined to just the immediate area : there would be evidence all over the place, if you knew what to look for. Like consistent C14 dating curves that don't accord with theory - which they don't.
Massive radiation would be expected to cause major mutations in plant life. Maize probably evolved by macro-mutation at that time, and plant domestication of possibly mutated forms appears worldwide after the Late Glacial period. For example, there was a rapid transition from wild to domesticated grains in the Near East after the catastrophe.
There may be a more prosaic explanation. But follow-up data has tended to increase, rather than decrease, the probability that this explanation is correct.
Decisively, at the Lewisville, Texas, Paleo-Indian site there is in fact a perfectly reliable radiocarbon date of ~ 26,600 bp rcy obtained in 1985. It is common knowledge in the archaeological community that Paleo-Indian artifacts are distinctive, and cultural markers of a "window in time." Since the Lewisville site is "at least" 26,000 years old, younger Paleo-Indian radiocarbon dates cannot possibly be correct, and the construct that maintains Paleo-Indian is confined to ~ 12,000 years therefore also must be incorrect, and should be discarded immediately. Using common sense, if prehistoric peoples arrived in North America first and then migrated to Central and South America, 14C dates at lower latitudes "must be" younger. In fact, South American radiocarbon dates approach ~ 30,000 bp rcy. Lewisville "fits" while younger Paleo-Indian dates in North America do not, and therefore all must be incorrect (for some reason).Interesting, No? But don't worry, if it had happened, it would be an unusally severe event for its kind. And the world survived. It probably wouldn't happen again, or at least, not as badly. The only ones who would have to worry anyway would be those living above 50 North latitude, or below 50 South latitude, and the latter is almost unpopulated. The former of course includes Canada, Russia, and the Northernmost states of the USA.
Radiocarbon dating works "perfectly well." However, it derives dates from the amount of 14C present. But, there definitely are anomalies by latitude/longitude/depth in sediments that authoritative archaeologists have noted for many years. It is clear that both communities are correct, and interdisciplinary collaboration in the pursuit of scientific truth stongly is encouraged. Additionally, this short piece hopefully will serve as a reminder to all, both avocational and otherwise, to be more "open-minded" in the pursuit of patterns to factual scientific data rather than adherence to "dogma," and for everyone to consider data within the broader framework of a holistic (rather than "particularist/reductionist") point of view.
I'm starting to really appreciate Australia as a nice place to live.