hancock defant
Dr. Marc Defant did a great thing this morning by announcing on Twitter and his blog that he had come around to support the Younger Dryas Impact Hypothesis. As I told Marc, my respect for his intellectual integrity soared when I saw his tweet:

Defant's reversal on the YDIH after his public skepticism is good science in action. Unlike politics, where people pick sides (and stick to them come what may), Marc clearly operates according to the best traditions and underpinnings of reason, where any position is subject to persuasion given sufficient data and appropriate interpretation.

In an admirable twist, Marc credits his reassessment of the Younger Dryas Impact Hypothesis to a recommendation from his Joe Rogan debate adversary, Graham Hancock, to read a recent book by James Laurence Powell. It's not surprising that Defant was persuaded by the book. Dr. Powell is also a former YDIH skeptic, and Deadly Voyager has become the essential read for the subject. (Unless you care to pick your way through every paper on The Bib.)

Good for Dr. Defant, good for the YDIH, and good for Science — the system works!

From Defant's blog "Enfold":
In my debate with Graham Hancock on the Joe Rogan Experience podcast (beginning at 2:03:43) and a critique of Graham's book I wrote for Skeptic magazine along with further details on my website, I found myself dealing with the veracity of the Younger Dryas Impact Hypothesis (YDIH). I was skeptical of the hypothesis but stated the following in my Skeptic paper:

"...the debate proceeds in the proper scientific manner (i.e., by publishing results in peer-reviewed scientific journals). As Malcolm LeCompte, one of the comet researchers, pointed out in our debate... there are four indicators at the YD boundary that may be due to an extraterrestrial origin: nanodiamonds, magnetic sphericals, melt glass, and the platinum group metals."

My major problem with the YDIH was the claim that the megafauna and Clovis culture went extinct as a result of the proposed comet strike. I noted in the Skeptic paper "Scientists have also been a bit incredulous that a comet strike could wipe out all the megafauna as far south as Patagonia, while leaving mammoths alive and well on St. Paul Island, Alaska until 3,700 years ago."

I recently had some correspondence with Graham, and he suggested I read a recent book by James Lawrence Powell entitled Deadly Voyager: The Ancient Comet Strike that Changed Earth and Human History (2020). It is a superb book and has absolutely convinced me there were comet airbursts at the Younger Dryas. And the airbursts probably killed the megafauna which in turn, caused the Clovis culture to cease existence (partly by diminishing human numbers but also because there was no need to have Clovis spearheads that could kill nonexistent megafauna). I have not been keeping up with the debate since 2017, and so I was thrilled to see the new evidence that has come to light and the lack of scientific merit in the studies that attempted to dismiss the hypothesis.

I recommend the book — it is a fascinating read. The evidence is overwhelming and nicely collected and summarized by Powell. It is clear that the Pt signature shows up precisely where it is expected about 12,900 years ago in all the sites, and high-pressure nanodiamonds, melt glass, carbon from forest fires, magnetic sphericals, etc. show up precisely where they are expected over 4 continents. I also have to admit the YDIH is an extremely good argument that the megafauna died out from the comet airbursts and the Clovis culture was impacted. The forest fires alone wreaked havoc across the continents. The mammoth existing on St. Paul Island seems to be a minor incidental when compared to the other evidence. And a crater is not required - no wonder they don't find shocked minerals — the airbursts would have kept earth materials out of the equation.

Finally, the Hiawatha crater that has recently been discovered below the Greenland Ice sheet may or may not be related to the YDIH. But it is not needed to explain the evidence.

Of course, all of this does not change my views of Graham's two most recent books. I enjoyed reading his latest entitled America Before (2019) because it is well written and his knowledge of archaeology is superb. But as I say in the Skeptic article: "To be clear, the [YDIH] debate is not over lost civilizations." So although I consider Graham a friend, I disagree with his lost civilizations scenario with all the respect he deserves."
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