Experts certified two years ago that Monte Verde in Chile is the oldest
       archaeological site in the Americas — and the story of humans in the
       New World was rewritten. Now Monte Verde faces a scientific
       challenge. Here is the challenge, responses to it, and comments on
       the debate.

       From the Editors of Scientific American Discovering Archaeology

       Monte Verde, near the southern tip of Chile, is arguably the most
       important archaeological site in the New World — a landmark
       excavation that shattered a paradigm that for 70 years had explained
       the peopling of the Americas.

       Conventional wisdom had been that the first humans to enter the
       Americas were hunters of the Clovis culture who crossed the then-dry
       Bering Strait into Alaska about 13,500 calendar years ago. They are
       named for the New Mexico site where their trademark fluted spear
       points were first found. Before them, the New World was untouched by
       humanity.

       But the ancient settlement that archaeologist Tom Dillehay found on
       the banks of Chinchihuapi Creek, more than 10,000 miles south of the
       Bering Strait, yielded radiocarbon dates about 1,000 years older than
       the oldest Clovis sites. He reported evidence of wood-framed,
       hide-covered structures, along with stone tools, hearths, wooden
       implements, butchered mastodon bones, knotted twine and cordage,
       and other artifacts.

       (Dates in archaeology typically are presented in radiocarbon-dated
       years before present — "rcbp." They can be calibrated to calendar
       years before the present, which are identified as "cal BP." Thus, the
       Clovis barrier is at 11,500 rcbp or 13,500 cal BP.)

       The question of who were the New World's first immigrants and when
       they arrived was thrown wide-open for the first time since 1927.

       But most scientists hate to walk away from a paradigm, particularly
       one that has served as long and as well as the formidable "Clovis
       Barrier." Those who would challenge such a paradigm face prolonged,
       meticulous examination and occasionally stubborn resistance. That is
       exactly what Dillehay, now of the University of Kentucky, met when he
       reported results of the Monte Verde excavations he began in 1977.

       But in 1997, a panel of 12 eminent experts in early American
       archaeology studied Dillehay's evidence and visited the site. They
       concluded Monte Verde was indeed a habitation site and that it
       predated the Clovis culture. The long debate was over, and the Clovis
       paradigm was shattered.

       But now the Monte Verde site is being challenged again — in
       considerable detail. Stuart J. Fiedel, an archaeologist with John Milner
       Associates who has published widely on the prehistory of the
       Americas, analyzed the two epic volumes in which Dillehay documented
       every aspect of his site. Fiedel's conclusion: Problems with Dillehay's
       documentation raise questions about the provenience (the location, in
       both space and time, from which it came) of virtually every
       "compelling" artifact Dillehay cites. Fiedel considers the alleged
       shortcomings crippling if not fatal to the Monte Verde site.

       Scientific American Discovering Archaeology is publishing, in this
       special section, the full text of Fiedel's report. Dillehay (and many of
       his colleagues) and Michael Collins, an important co-author with
       Dillehay on some Monte Verde reports, accepted our offers to write
       formal responses to Fiedel's paper. We also invited seven widely
       acknowledged experts to comment on the renewed debate. This is a
       highly unusual venue for the initial presentation of such a scientific
       disagreement, and we at Scientific American Discovering Archaeology
       did not take this step lightly. We acknowledge that publishing these
       papers bypasses the tradition of peer review, which is required for
       publication in scientific journals, and we accept that we may be
       criticized for doing so.

       However, after a great deal of discussion among our staff and after
       seeking the advice of trusted experts, we concluded the issue is of
       overwhelming importance to our understanding of the peopling of the
       Americas, and that rumors of the work inevitably would lead to informal
       and perhaps misguided discussions without input from all parties. Here
       are the arguments, the responses, and the discussions.

       Additionally, one of the most important conferences on New World
       prehistory in more than 50 years — the Clovis and Beyond symposium
       in Santa Fe October 28-31 — will assemble most specialists on the
       topic to discuss the state of knowledge about when and how the New
       World was settled. We felt it was extremely important that
       participants in that conference have this information available in its
       entirety.

       Scientific American Discovering Archaeology has absolutely no position
       on the issues raised in this special section, and publishing it in no way
       implies confidence or doubt about any opinions expressed. Our only
       purpose is to present this information accurately, fairly, and quickly.