A response to Napier and Howard and the Younger Dryas impact hypothesis

As I have indicated in an earlier blog, I wrote an article about the conjectures Graham Hancock makes in his book entitled Magicians of the Gods for Skeptic magazine (Conjuring Up a Lost Civilization: An Analysis of the Claims Made by Graham Hancock in Magicians of the Gods).   I also appeared on the Joe Rogan Experience (JRE) as a guest of Michael Shermer to debate Graham Hancock and Randal Carlson.    I never realized just how popular Hancock was and is until I read some of the downright hostile and vitriolic comments directed at Michael Shermer and me after we were on the JRE.  I posted some of them on my Facebook page to amuse my friends and family.  I should point out that although I don’t like being the brunt of hate speech, I firmly believe in their freedom of expression.  Having said this, I did take seriously a comment made by Bill Napier, an astronomer who is a honorary professor of astrobiology in the Center for Astrobiology at Cardiff University.  Napier has published several articles on the Younger Dryas Impact Hypothesis (YDIH).  He submitted a letter to a website called the Cosmic Tusk which is owned by George Howard.  Howard is one of the co-authors on the Firestone et al.[1] paper – the first article which postulated a comet impact about 13,000 years ago.  It would appear that I ruffled both Howard and Napier’s feathers in questioning the scientific validity of the comet strike on the JRE.  The article is entitled Open Letter: Napier on Defant and the Joe Rogan Podcast.  Of course, Hancock, who has an article presented on the site, wasted no time in referencing the comments by Howard and the letter by Napier to support the validity of his position.

Let me repeat what I stated in my Skeptic article.  Although I remain open minded about the possibility of a comet strike 12,900 years ago, I am extremely skeptical that it had an impact on the Clovis culture or the megafauna of North and South America.  I also applaud the scientists who are proponents of the comet strike for their handling of the YDIH by publishing results in refereed scientific journals.  Because Hancock has latched onto the hypothesis to explain supposedly how Atlantis was destroyed, I had to get into the details of the scientific debate on the YDIH.   My position is that there is still a great amount of controversy in the literature surrounding the hypothesis, and I don’t wish to become an advocate for either side until the debate has played itself out in the literature.  This is how science works.  But there is little doubt in my mind and apparently in Napier’s mind based on his comments, that the comet strike (if there was one) had nothing to do with lost civilizations.

The most important point I want to address is Napier’s claim that I incorrectly described how comets break up when I was on the JRE.  He states: “Marc Defant told us that “the comet guys are getting hit pretty hard,” but alas, he backed this up with a blatantly wrong description of comet evolution.”  I did not specifically talk about comet evolution nor did I try to show “the comet guys” were wrong.  I simply suggested that there were problems with some of the postulates including how comets break up.  I stated: “It [Comet Shoemaker-Levy 9] broke up because of the gravitation of Jupiter.  You would not expect them [comets] to break up entering into the [earth] atmosphere… and then separate.”   In other words, it is difficult to explain with physics how a comet entering the atmosphere would disperse after it breaks up through a proposed airburst so that megafauna and the Clovis culture would be affected over two continents.  Napier claims that “Marc and Michael seem to have been misled by unrefereed nonsense from a few people with no expertise or track record in cometary dynamics, and ignorant of its extensive, long-running literature.”  Perhaps Napier misunderstood what I was saying.  I carefully read the YDIH literature prior to the paper I wrote for Skeptic and my appearance on the JRE.  The comments above were specifically taken directly from a paper published in a refereed scientific journal (J. of Quaternary Science) by Holliday et al.[2] – some of the scientific opponents of Napier and Howard.  I quote from the Holliday paper: “No physical mechanism is known to produce an airburst [an exploding comet]  that would affect the entire continent… They [referencing Wittke et al.[3] who propose a model for the breakup of a comet] state that the impactor probably broke apart in solar orbit before encountering Earth, as do most comets ‘including Comet Shoemaker-Levy 9’.  However SL9 was orbiting Jupiter, not the sun, when it broke apart, and, moreover, most comets do not break up in solar orbit.  The reason that all the fragments of SL9 collided with Jupiter is because they were in orbit around Jupiter.  The processes that led to the multiple impacts on Jupiter do not apply to comets in solar orbit or for approaches to Earth… Moreover, a spontaneous breakup in solar orbit, such as Comet 73P/Schwassmann-Wachmann would have had to be exquisitely timed in order for an expanding cloud of debris to strike the Earth.  Dispersed impacts of multiple fragments would be at least 1000 times less frequent (probable) than the impact of a single nucleus, which is already an extraordinarily rare impact”.

main-qimg-1e3b60f1af94711de6ed99830fc9e33a-cDark areas on Jupiter where Comet Shoemaker-Levy 9 hit.

It is true that I am not an expert on comet dynamics, but I know how to read and understand the scientific literature.  I am going to presume that Napier misunderstood my position and that although he may disagree with Holliday et al., my statements were based on their refereed scientific article.  In fact, Holliday et al. challenge Napier et al.[4] in their paper for suggesting that “passage through a cluster of fragments from a broken comet would probably ‘yield several impactors with energies up to 5,000 megatons, fully adequate for surface melting’… However, cometary impactors of this energy would be about 1 km in diameter and there is no physical mechanism to prevent them from striking the ground and forming 10-km diameter craters.”  Of course, I also addressed the lack of craters at the YD boundary when I was on the JRE.  I would only add that Napier might be better served by addressing Holliday et al. and other scientists directly involved with the YDIH in the scientific literature as opposed to publishing letters in the Cosmic Tusk – a site that clearly appeals to a nonscientific audience interested in the speculative and supernatural.

It does not appear that Napier had a hidden agenda in criticizing me, but I wish I could say the same for Howard.  His comments are characteristic of some of the vitriol I received from the general public for simply disagreeing with Hancock – not the kind of professionalism one might expect from a person who lauds himself as a scientist (and skeptic of all things).  I honestly think it is unbefitting of me to address ad hominem and sarcastic attacks like “Defant showed zero humility and spoke of comets with the familiarity of a volcanologist.”  However, I do think it is instructive for my students to see that “scientists” are human and sometimes resort to personal attacks rather than addressing the details of the science.   Basically Howard is engaging in silly turf wars where credentials and opinion of behavior become more important than the scientific rigor of what is being said.  As far as I can tell, Howard has a BA degree in political science from the University of North Carolina so I am not sure he should be throwing rocks from his proverbial glass house.  One wonders how he can make the claim that “He may or may not know it, but Defant’s received wisdom… is 1960’s [sic] grade school comet science [sic]” (I refer the reader to my discussion above in refutation of the few actual scientific criticisms Howard makes – basically a repeat of what Napier says).

Walter Alvarez, a structural geologist, and his father Luis Alvarez, a physicist (passed), were responsible for discovering the impact of a 10 km meteorite that hit earth 66 million years ago and led to the eventual extinction of the dinosaurs.  I wonder if Howard dismisses their discovery because they were not astronomers?  Two geochemists also participated in the discovery which is my specialty (I am a professor of geochemistry and my PhD is specifically in that field) – I apply geochemistry to volcanic rocks to understand processes within the earth.  Had Howard taken the time to research my background before he made his attacks, he would have found my book Voyage of Discovery: From the Big Bang to the Ice Age (about the history of the universe, earth and life), my general science course entitled Origins, my video lectures particularly on astronomy (including comets), and my Tedx talk on Why We are Alone in the Galaxy as some evidence that I might know a bit more about the subject than “grade school comet science”.  I note that Howard’s contention in the Firestone et al.[5] paper that the formation of the Carolina Bays (his claimed area of research) by comet strikes 12,900 years ago has been thoroughly debunked based on new dating[6].  It would be unprofessional on my part to attribute his incorrect interpretation of the Carolina Bays to a lack of understanding because he is a political scientist, so I won’t.

I find it ironic that Howard claims to be a skeptic and yet publishes (and links) to a paper by Hancock who, among other things, touts his lost civilization: Hancock on the Younger Dryas Impact Hypothesis since 2007.  Let’s not forget that Hancock claims that we are in mortal danger until 2040 from another comet strike based on interpretations he makes from so-called asterisms at Glöbekli Tepe.  Apparently Hancock, a self-described reporter with an undergraduate degree in sociology (see the JRE starting at about 2:12:47 where we are discussing the Mayan calendar – he claims to be just a reporter) has more bonafides than a “volcanologist” in Howard’s mind.  Hancock’s credentials notwithstanding, I hardly think Howard can consider himself a skeptic when he allows someone to tout fantastic unsupported stories about lost civilizations on his website.  I presume the Cosmic Tusk is more interested in giving a voice to people who agree with Howard, regardless of their far-fetched notions about the supernatual, than scientists interested in physical reality.


[1] Firestone, R. B., et al., 2007. Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. Proc. Natl. Acad. Sci., v. 104, 16016-16021.

[2] Holliday, V. T., et la., 2014. The Younger Dryas impact hypothesis: a cosmic catastrophe. J. Quaternary Sci., v. 29, 515-530.

[3] Wittke, J. H., et al., 2013, Evidence for deposition of 10 million tonnes of impact spherules across four continents 12,800 years ago: Proc. Natl. Acad. Sci., v. 110, p. E2088-E2097

[4] Napier, W.A., et al., 2013, Reply to Boslough et al.: Decades of comet research counter their claims: Proc. Natl. Acad. Sci., v. 110, p. E4171.

[5] Firestone et al., 2007,  op cit.

[6] For example, Meltzer, D. J. et al., 2014, Chronological evidence fails to support claims for an isochronus widespread layer of cosmic impact indicators dated to 12,800 years ago: Proc. Natl. Acad. Sci., v. 111, p. E2162-E2171.

3 replies
  1. Dwaine
    Dwaine says:

    To add to George’s very detailed and well put criticism, it would have served you better had you actually read Firestone’s paper. Just by skimming through and then making comments on misread points is pointless and it makes me think how on earth did you get through the university???

    Firestone et al NEVER suggested that the Carolina Bays were a byproduct of the cosmic impact. They only said that they had a look at it, they did find the mat layer but in some, not all fo the Bays, and they recognised the previously performed dating of the Bays, which was not in sync with the impact dates. Firestone et al made it perfectly clear that they were not convinced that the Bays are impact craters, nor that they were made at teh onset of the Younger Dryas mini icae age.

    If you want to participate in this debate, do us all, yourself included, a favour and familiarise yourself with the results and the claims of the parties you wish to debate with. You may discover that your opinion may meet with less resistance and more productive discussion.

  2. Glyptodon
    Glyptodon says:

    First, concerning the lack of a crater, even if there might be a possible explanation for the lack of a crater, it still does not absolve a person from having to provide some sort of convincing evidence that some sort of impact occurred. Regardless of the reason, lack of evidence is still lack of evidence. However, unlike Dr. Zamora, at least you seem to agree that Michael Davias’s “Saginaw Impact Crater “is a completely imaginary entity.

    Second, in reference to the “…scouring effects of flood waters in Washington and Montana…” in which “solid bedrock has been thoroughly eroded…” there is an abundance of evidence including bounding unconformities within flood deposits; the presence of paleosols, including interglacial calcretes associated with these unconformities; terrestrial trace fossils also associated with these unconformities; magnetostratigraphy, radiocarbon dates, optically stimulated luminescence (OSL) dates, terrestrial in situ cosmogenic nuclide dates, offshore turbidites, and unconformity truncated clastic dikes that provide well documented proof of innumerable and multiple megafloods over at least the last 1.5 to 2 million years. Recent cosmogenic dating of boulders moved by the Missoula Floods demonstrate that the largest boulders were last moved by Missoula megaflooding about 18,200 years ago and the last of the megafloods from Glacial Lake Missoula occurred between 14,000 to 14,400 years. For some of the details, go see:

    Balbas et al., 2017, 10Be dating of late Pleistocene megafloods and Cordilleran Ice Sheet retreat in the northwestern United States: Geology, doi:10.1130/G38956.1.

    Third, you also wrote about “Thousands of mammoths and other fauna have been unearthed in Siberia; most show evidence of traumatic physical injuries and sudden death…”

    Extensive research has been conducted on these remains have indeed shown that there are indeed the bones of thousands of mammoths and other fauna and the remains and of a few dozen mummified remains of them to be found in Siberia. However, there is deafening lack of reliable sources that provide any credible evidence of simultaneous, widespread traumatic physical injuries and sudden death among the Siberian megafauna that are part of a single regional event. Such claims are the result of the repetition and recycling of bad data and largely fictional “alternative facts” without any vetting of their validity by biblical creationists, a wide variety of catastrophists such as Ivan T. Sanderson, Charles Hapgood, Randall Carlson, and I. Velikovsky, and the writers of popular lay books such as David Childress and Graham Hancock.

    Fourth, some catastrophists are completely lost in time and space as there now exists overwhelming evidence provided by numerous radiocarbon dates, OSL dates, stratigraphic relationships, and other observations that the “thousands of mammoths and other fauna” that Mr. George write about died either singularly, at best a few possibly as part of as herd, over a period of hundreds of thousands of years to over a million years and, thus, cannot possibly be the result of a single catastrophe. For example, the Beresovka mammoth that Randal Carlson discusses at length in Joe Rogan Experience 501 died circa 44,000 years ago and, thus, definitely cannot be associated with a hypothetical Younger Dryas catastrophe. Similarly, the Hot Springs (South Dakota) that Randal Carlson has talked about also on podcasts greatly predate Younger Dryas and similarly cannot be connected to the start of it.

    For a detail discussion of the facts related to the “thousands of mammoths and other fauna” that
    were previously written about above, go see:

    Bishop, S., no date. Woolly Mammoths: Evidence of Catastrophe? Talk.origins Archive

    Colavito, J., 2016, Flash-Frozen Mammoths and Their Buttercups: Yet Another Case of Repetition and Recycling of Bad Data, jasoncolavito.com, blog.

    Farrand, W.R., 1961. Frozen mammoths and modern geology. Science 133: 729-735.

    Guthrie, R.D., 1990. Frozen Fauna of the Mammoth Steppe, 1990, University of Chicago Press, Chicago, Ill.

    Thorson, R.M. and Guthrie, R.D., 1992. Stratigraphy of the Colorado Creek mammoth locality, Alaska, Quaternary Research 37:214–228. (see page 21)

    Ukraintseva, V.V., 1993. Vegetation Cover and Environment of the” mammoth Epoch” in Siberia. Mammoth Site of Hot Springs.

    Fifth, both Randal Carlson and Graham Hancock have also overlooked other essential and basic research. For example in case, in terms of the “haystack boulders,” e.g. Yeager Rock, of Boulder Park National Natural Landmark, Washington (state), Graham and Randal pontificate in the book about them having been moved by massive catastrophic flooding. However, they completely ignore the absence of sediments or landforms associated with megaflooding and the presence of glacial till as a ground moraine underlying the haystack rocks and well defined glacial landforms. It is quite obvious that the haystack rocks are readily explained as having been moved by a glacier, not megaflooding. These boulders and associated glacial erratics were dumped by the retreat of the Okanogan ice lobe and, thus, cannot possibly be associated with a Younger Dryas megaflood.

    Finally, in Graham’s latest book, Randall Carlson talks about the Palouse Loess as having dropped from the sky as muddy rain as the result of a Younger Dryas Impact. In the book, there is no mention of published, well-documented evidence that completely contradicts such an origin. This includes radiocarbon dates, OSL dates, interglacial paleosols (calcretes), abundant trace fossils of plants and insects, textural trends, mineralogical analyses (trends) and so forth. Concordant radiocarbon, OSL dates, and dated volcanic ash beds demonstrate that the uppermost layer of Palouse loess accumulated episodically between about 77,000 and 15,000 years ago long before the start of the Younger Dryas.

    Obviously, there is still a bunch of objective evidence about Quaternary geology that both Graham and Carlson have overlooked and need to read about and explain. (For example, they need to explain how a Clovis Site can be found on top of a Missoula megaflood megabar near Wenatchee, Washington, if their chronology is correct.)

    By the way, PDFs of papers about the thermoluminescence and Optically Stimulated Luminescence dating of Egyptian and other monuments can be found at https://www.researchgate.net/profile/Asimina_Vafiadou

  3. George
    George says:

    I suggest that the discussion would have been better served had you not approached it with the intention of smearing those you disagree with.

    First, your repeated use of reference to “peer review” as a bludgeon is disingenuous. As you are no doubt aware, peer review has been thoroughly discredited as a control and review mechanism in science. This is due to the rampant fraud, misrepresentation and “pal review” which has infested all of science. Consequently, no reputable scientist relies on peer review as a qualifier on any research. Certainly, no reputable scientist uses “peer reviewed” as evidence regarding the legitimacy of a position. However, it is commonly used as a political club in the battle of egos in an attempt to discredit opponents.

    Second: while I defer to the experts regarding the fragmentation dynamics of comets, I draw your attention to the foundation of the impact theory. That is, the earth passes through the comet debris twice a year. This being the case, it is possible that several fragments can be on a similar trajectory and impact the earth. Multiple impact theory does not require the fragmentation of a single entity.

    Third: granted, no impact crater has yet been found on the North American continent. This is hardly surprising since current theory stipulates that the points of impact would have been covered with up to two miles of ice. This would have been more than sufficient to absorb the impact, and provide the melt water. If any impact effects did reach the underlying ground surface, the dissipating melt water would scour away any evidence of this impact. Take note of the scouring effects of flood waters in Washington and Montana; solid bedrock has been thoroughly eroded.

    Fourth: the impact effect on the mega fauna is self evident. Thousands of mammoths and other fauna have been unearthed in Siberia; most show evidence of traumatic physical injuries and sudden death. Given both the geographical extent of the dead animals, and their sheer numbers, it is indisputable that they were killed by a sudden catastrophic event. To suggest that these circumstances were precipitated by humans is ludicrous.

    The above points are just a few that relate to the impact hypothesis. The cumulative effect of multiple streams of evidence from multiple sources gives the impact hypothesis a high level of credibility. What is required is that all interested parties stand back and take an objective view of the evidence; something that is currently lacking as the wagons circle. If, as a consequence, objective evidence is presented that nullifies the impact hypothesis, then good. That is science. The current clash of egos serves no-one.

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