A quite perfectly delightful hypothesis holds that air bursts and perhaps direct impact on solid earth by a comet or comets 12,000-plus years ago triggered climatological spasm on Earth while pushing North American megafauna such as mammoths over the brink to extinction. Comet showers have surely happened. The animals did die as did the iconic big-spear-toting Clovis Culture that is the first human culture to have left a large archeological footprint in what is now the US and Canada. It’s a dramatic marriage of possibility and fact.
Since first presented in 2007 via a report at an American Geophysical Union meeting in Mexico and in the Proceedings of the National Academy of Sciences – the favored journal for the proponents of the theory – it has gotten repeated plays in the press and encountered doubt from many other authorities. But lately it can’t seem to get much of a media bounce. Perhaps, as stated again below, we can get some science journalists to share with us their thoughts why that is.
This week brought another opportunity, just three months after the last round (see Earlier Post, March 19). This today makes at least a dozen posts that ksjtracker has run on the idea’s news stories (whole list). The latest paper in PNAS is large, has 18 authors with the lead at the US Geological Survey and others at respected institutions. It doubles-down on the authors’ conviction that their science is robust. They report high-energy scars in the grains of sediments 12,900 years old from a broad range of sites around the world, shocked crystals, glassy melts, rare minerals found in meteorites and that form only at high temperatures – high enough to boil quartz – indications of major fires, and tiny particles that appear to have collided with one another violently.
The authors worked mainly under grants from the NSF. It doesn’t give money to just anybody. The key set of distinctive minerals and disturbed rock, it says, are easy to explain given the physical conditions in and near large impacts and atmospheric nuclear bomb tests but little else. The paper’s abstract declares emphatically that the evidence is “inconsistent with anthropogenic, volcanic, authigenic [formed during normal sedimentation/cp], and cosmic materials yet consistent with cosmic ejecta, supporting the hypothesis of extraterrestrial airbursts/impacts 12,900 years ago.” The wide distribution of distinctive impact-spewed spherules of that age around the world, but rare in sediments younger or older, “is consistent with multiple impactors.” UC Santa Barbara, where the man credited as the paper’s primary writer works, distributed a press release that calls the assembly “the latest to strongly support the controversial Younger Dryas Boundary hypothesis” of large impacts as driver of extinctions. That includes the period of rapid global cooling, called by geologists and paleoclimatologists The Younger Dryas, that delayed Earth’s emergence from the last ice age.
But coverage is scant, with just one major and mainstream media outlet included:
- Los Angeles Times – Thomas H. Maugh II: New evidence that extraterrestrial impact killed off the mammoths ; Maugh reports the controversy that has accompanied this hypothesis since its debut, but in his lede adds that this new paper’s results “appear to provide .. replication” that doubters have called for. It may have been even better replication had it not come from the same general group that has been reporting this scenario – and meeting head winds from some colleagues – all along.
- Daily Mail (UK) Meteorite storm ‘smashed the Earth 12,000 yaers ago and killed off a prehistoric people.” Looks mainly to be press release rewrite, with some colorful phrasings.
That’s about it other than very short renditions, blog posts, and relays of the original UCSF press release below in Grist.
A correspondent of mine, an author of the paper, has felt that over the years major media and their science journalists have failed to appreciate the importance of the evidence for the killer-comet idea. Coverage has faded dramatically since 2007. Or has he put it in an initial email:
The elites of your tribe are an embarrassment. They would dig graves for the living if given the chance.
He followed up with a more tempered email including:
Journalists should not wait to report good science until there is “enthusiasm” among scientists. People want to hear more about controversial discoveries, particularly those that are published by multi-disciplinary teams in top journals, and contradicted by same. Controversial stuff in top pubs should have brought critical mass in this case.What’s going on here is that journalists: 1) do not understand the fundamental implications to earth and human history, 2) are reluctant to delve into the implications for other more popular societal threats posed by political policies, and 3) think they and their researcher buddies, if not knowing it all, know enough to understand when nothing more “big” need be known, and this one of those cases.
Other Mammoth Extinction News: Nature Communications has a report that blames a concatenation of reasons for the megafauna extinctions that included mammoths.
- LIveScience – Charles Q. Choi: Mammoths Wiped Out By Multiple Killers ; The comet is not among the causes that the new study focusses upon. Choi mentions that idea however – and links to one of his previous stories detailing one flaw in the impact hypothesis.
Grist for the Mill (from different University of California campuses):
On Clovis, Comets and Collision as in PNAS: UC Santa Barbara Press Release ;
On slow-developing other reasons for Mammoth demise, as in Nature Communications: UCLA Press Release ;
– Charlie Petit
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