Nexus - 0505 - New Times Magazine-pages

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ing from theory to fact, then throwing out the facts that don't fit, Cynthia Irwin-Williams wrote: "These [bifacial] tools surely were not in use at Valsequillo more than 200,000 years before the date generally accepted for development of analogous tools in the Old World, nor indeed more than 150,000 years before the appearance of Homo sapiens." Privately, she referred to those of us involved with dating the site as "the lunatic fringe".'* She ceased all communication with us from that time forward. “> Seinen —iiteinaneneenaneaeannanenenaea. iams wrote: Fortunately, the scientists working in Africa had faced a similar Cynthia Irwin-Will problem to ours and had come up with several radiometric dating "These [bifacial] tools surely were not in use at Valsequillo methods besides the unsuitable “C method. And most of those more than 200,000 years before the date generally accepted for methods required volcanic ash! development of analogous tools in the Old World, nor indeed In 1973, early sites in Africa were commonly dated radiometri- = more than 150,000 years before the appearance of Homo cally using materials from overlying volcanic layers. The potassi- —_ sapiens.""* um-argon method was popular, but it required lava flows and/or Privately, she referred to those of us involved with dating the potassium-rich mineral crystals. We had neither at Hueyatlaco. site as "the lunatic fringe".'* She ceased all communication with But we did have tiny zircon crystals (very tiny, about the size of _—_us from that time forward. a grain of sugar) in the tephra samples. This meant we could use the zircon fission-track dating method on the younger volcanic PUBLICATION WOES ash and pumice layers exposed in the archaeologic trenches. If this were a perfect world, the Valsequillo players would have Dates for these sat down at the same tephra units would table and debated give a minimum age . , * the issues publicly until the truth came out. But it isn't. And we didn't. Cynthia Irwin- Williams was an establishment anthropologist with degrees from presti- gious schools and influential friends in the east. Iwasa geologist with a PhD from a small western for the underlying, older artifact beds. In 1973 Chuck Naeser, another geo- chemist with the USGS, offered to run the zircons for us. We didn't ask him for precise data at the time, as that would have required weeks of hard labour. We only fe: : wanted "the big pic- Qyerview of the Hueyatlaco site in 1973 during excavation to expose the sedimentary layers and to WNiversity and my ture": to know if his collect samples for zircon fission-track dating. The artifact-bearing beds appear at lower left; the dad was a meat cut- zircon dates would volcanic ash and pumice layers occur in the overlying (younger) sediment cap, visible at middle ter. Her friends, fall closer to and upper right. (Photo by Hal Malde) especially her men- Barney's "impossible" 250,000-year uranium-series dates or to tor H. Marie Wormington, advised her to ignore me and the whole Cynthia's "politically correct" 22,000-year date. geological thing and preach the 22,000-year date for all her sites. The dates came back with two sigma numbers—meaning that And she did." statistically there is a 95 per cent possibility that the actual mea- Meanwhile, we geologists were having a hard time getting our sured date falls within the stated range. Even with a large plus or _ old dates for the sites into print. We started out well with an minus value, Chuck's dates agreed with Barney's: 600,000 + exciting news release in the fall of 1973. The story was picked up 340,000 years for zircons from an overlying pumice-rich mudflow by the wire services and quickly circled the globe. But then, layer; 370,000 + 200,000 years from an overlying air-fall ash when it came to the critical research paper, it was one delay after layer.” Cynthia's wishful-thinking date of 22,000 years was out —_ another. of the running. From 1975 to 1979 we I was elated! Several = waited for the paper to be lines of geologic evidence, rinted in a scientific book. including six radiometric After four years, the third dates, placed big-game editor decided not to pub- hunters in Mexico a quar- ish the book at all. The ter-million years ago. As manuscript was returned. far as I was concerned, it In 1980 I submitted the was an open-and-shut case. paper to the editor of a pop- How naive I was! ular science magazine who ad requested it. After sev- eral months' delay, he regretted that "the manu- script had fallen down ehind the file cabinet and had been lost". It was ESTABLISHMENT DENIAL It was the geologists ver- sus the anthropologists; fact versus theory. Geologic evidence said the returned. Valsequillo sites were old. By 1980 my career as a Entrenched theory said the Representative artifacts from Hueyatlaco. : research geologist was suf- sites were young. Left: edge-retouched tool. Right: bifacial tool. The edge-retouched tool is older. fering. My professional In a classic case of argu- (Photos by H. 8. Rice: Inwin-Williams estate) correspondence, both 58 + NEXUS ELATION OVER ZIRCON FISSION-TRACK DATES AUGUST - SEPTEMBER 1998