Tag Archives: comets

Still no Clovis Comet

Oh noes, my tusks are on fire. Source: wincustomize.com

I talked once before about the “Clovis Comet” theory, which suggested the widespread extinctions of megafauna in North America at the end of the last ice age was caused by a large comet impact.  At the same moment, the highly distinctive “Clovis” archaeological culture was terminated.  It was suggested this comet might have either airburst or struck the ice sheets, in either case not causing a visible crater.  However, abundant “nanodiamonds”, said to be highly diagnostic of an extraterrestrial impact, were found at a widespread boundary layer roughly associated with the end of Clovis – the start of the Younger Dryas cold period when the earth was suddenly thrust back into near-glacial conditions.

So, I said then and I’ll say again now: this theory didn’t pass the sniff test from the beginning because it is another example of “Clovis exceptionalism” – the skeptical leeway that the Clovis-First model of first peopling of the Americas has been afforded by segments of the archaeological community.  No Clovis model was so implausible that it wasn’t given much respectful beard-stroking by the usual silverbacks.

Anyway, subsequent studies of the nanodiamonds and associated evidence have failed utterly to reproduce the findings.  Now comes even more news that the comet theory is unsupported and that the original investigators may have mistaken nanodiamonds for, among other things . . .  [drumroll] . . .  “hardened faecal material from arthropods.”

Continue reading

Clovis Exceptionalism Craters

An impactor (top) may have produced magnetic spherules (lower right), but similar spherules (lower left) continually fall from space.

An impactor (top) may have produced magnetic spherules (lower right), but similar spherules (lower left) continually fall from space.

John Hawks has a good writeup about the latest news on the theory put forward a couple of years ago that a comet impacted the Laurentide ice Sheets, overkilling Clovis culture, megafauna, and instigating the Younger Dryas Event to boot.  The new paper by Todd Surovell et al. completely fails to replicate a key bit of support for the theory, namely that magnetic iron spherules, said to be the comet’s smoking gun, were associated with terminal Clovis stratigraphy across the Americas.   Other studies have chipped away at the theory as well. I’m not an expert and it’s hard to judge the state of debate — though as Hawks notes, the paper is unusually unequivocal in its conclusions of ‘no evidence”.

I have to say, I don’t mind seeing more theories of Clovis exceptionalism shot down — it is an unusual archaeological phenomenon to be sure, but it hardly takes white-hot fallout across the Americas to bring it down.  Let’s start looking at Clovis on a more human scale! Enough with the megafaunal overkill models, when the most ubiquitous fauna associated with Clovis are turtles and tortoises.  Enough with the ignoring of plant remains — the Clovis Policemen’s longstanding refusal to accept Monte Verde tells us everything we need to know about their knowledge of ethnobotany.  Enough with the phallocentric failure to look beyond the Clovis Point to see that the rest of lithic Clovis  is pretty much a standard Upper Palaeolithic toolkit.

Smoked mammoth.

Smoked mammoth.

Thinking about that the other day,  I realized that Clovis is (ironically, counter-intuitively) ripe for a post-processualist analysis. Not a critique – an analysis.  Why?  What makes Clovis different is style – widespread projectile point style as a sort of hyperkinetic effort to maintain social cohesion through semiotics, if you like.  When something is so unusual we have to posit its arrival in a river of blood through the parting of a white sea, and then see it off with a rain of fire from heaven, surely it is time to turn it over to the school of archaeology that deals with histories, not generalities.

Surovell TA, Holliday VT, Gingerich JAM, Ketron C, Haynes CV, Jr, Hilman I, Wagner DP, Johnson E, Claeys P. 2009. An independent evaluation of the Younger Dryas extraterrestrial impact hypothesis. Proc Nat Acad Sci USA (early) doi:10.1073/pnas.0907857106 (subscription required)