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 World's End. Story by Charles E. Reineke.


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MacLeod goes on to describe how the core sample from Leg 207 shows a complete deposition; that is, an uninterrupted record of sediment deposits, during the time that the alternative hypothesis says multi-impacts should have occurred. No interruptions, he says, means no place to "lose" or "hide" evidence of other impacts. There is, on the other hand, clear evidence of a colossal event where the single impact hypothesis predicts one should be. "Here is a unique layer in these sections; here is the first few thousand years after that impact," MacLeod says, once again tracing his fingers along lines in the core. "Now, going on up, we see there is no other evidence for impacts, but we have wholesale extinction right at the level of the one impact deposit in this section."

Might this be enough to convince the doubters? Initial indications are no. In a Reuters story following publication of the journal article by MacLeod's team, Gerta Keller called their findings "hyper-inflated," saying they "do not withstand close examination."

MacLeod says he's not bothered by the statement, particularly since it has not been backed by any scholarly refutation. He says he has met Keller at conferences, and finds her to be "plenty nice, a very intelligent arguer."

In an e-mail last January, one of MacLeod's coauthors, Christian Koeberl of the University of Vienna, was less sanguine. "Let me just reiterate that the 'single impact theory' story is the consensus of the scientific community after three decades of research; the only ones who are sniping are Keller and her co-workers. In the 1980s, Keller did not believe in any impact. In the 1990s, she said Chicxulub is not an impact crater. Wrong on both counts. And now she wants multiple impacts, for which there is no evidence in the stratigraphic record."

For his part, MacLeod seems content to let the boundary experts have their say, though he acknowledges he's entered something of an academic minefield.

"I guess you could say passions run pretty high," MacLeod says with a shrug. "But so far, thankfully, I haven't gotten any envelopes with white powder in them."

End of story.
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©2007 Curators of the University of Missouri. Click here to contact the editor.