Jun 01,2007 00:00
Jim Barlow & Douglas Kennett
Did a comet hit the Great Lakes region and fragment human
EUGENE, Oregon - Two University of Oregon researchers are on a multi-institutional 26-member team proposing a startling new theory: that an extraterrestrial impact, possibly a comet, set off a 1,000-year-long cold spell and wiped out or fragmented the prehistoric Clovis culture and a variety of animals across North America almost 13,000 years ago.
"Highest concentrations of extraterrestrial impact materials occur in the Great Lakes area and spread out from there," Kennett said. "It would have had major effects on humans. Immediate effects would have been to the north and east (of the impact site), producing shockwaves, heat, flooding, wildfires, and a reduction and fragmentation of the human population."
The carbon-rich layer contains metallic microspherules, iridium, carbon spherules, fullerenes, charcoal and soot. Some of these ingredients were found worldwide in soils dating to the K-T Boundary, a clearly visible demarcation in soil dating to 65.5 million years ago. This K-T layer, noted for its iridium content, marks the end of the Cretaceous Period and the beginning of the Tertiary Period, when numerous species were driven into extinction after a massive asteroid struck Mexico's Yucatan Peninsula and the Gulf of Mexico.
Missing in the new theory is a crater marking an impact, but researchers argue that a strike above or into the Laurentide ice sheet could have absorbed it since it was less intense than the K-T event.
Kennett said that 35 animal genera, which are groups of similar or closely related species, went extinct at the end of the Pleistocene Epoch, which ran from 1.8 million to 10,000 years ago; at least, 15 of these extinctions occurred at about 12,900 years ago.
The Clovis impact, he said, would have caused major ecological shifts, driving human survivors into isolated groups in search of food and warmth. There is evidence, he said, that pockets of Clovis people survived in refugia, localized areas that had survived environmental changes, especially in the western United States.
"This was a massive continental scale, if not global, event," Kennett said.
He and Erlandson are currently evaluating the existing Paleo-Indian archaeological datasets, which Kennett describes as "suggestive of significant population reduction and fragmentation, but additional work is necessary to test this hypothesis further." Earlier research efforts need to be re-evaluated using new technologies that can narrow radiocarbon date range. As funding becomes available, new sites can be located and studied, Erlandson said.
"As we have grown more confident in the theory," Erlandson said, "we've been letting some of it out in informal talks to gauge the response to see where we are headed and what the initial objections are, which will help us to maintain our own objectivity."
The interest in pursuing both old and new leads could ignite a major surge of interdisciplinary questioning and attract a new wave of interested students, Kennett and Erlandson said.