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Comment by rfwhyte | Hacker News Reader

The only hypothesis I can come up with that lets me square the archaeological evidence (the numerous sites with pre-clovis dates) and the genetic evidence (almost all current North American indigenous population genetics derives from a single population that split off 17Kya) is that there's been multiple waves of people that have migrated into the Americas, and that either the events precluding or surrounding the Younger Dryas period contributed to a severe depopulating of the continent at that time, or that the most recent wave of immigrants almost entirely wiped out the previous population, as had they absorbed them I would assume we'd see more genetic evidence of that.

Personally I think the preponderance of archaeological evidence is strongly suggesting that there were absolutely people in the Americas pre-clovis, but the really interesting question from here then is who were they and what happened to them?

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The comet strike of 12,800 years ago neatly wiped out north American camels, horses, giant sloths, mammoths, mastodons, saber-tooth cats, dire wolves, the biggest bear and bison, cheetahs, and numerous other species, and neatly terminated all Clovis production. It would not be a stretch to guess it also wiped out most of the people making the Clovis points.

People living in southeast Asia 70,000 years ago were certainly sailing out of sight of land, because they reached and colonized Australia. It beggars belief to suggest they did not also go to other places in equally easy reach, and then others from there.

The article disgracefully trots out, once again, the "construction equipment" claim about the Cerutti mastodon site, despite its thorough refutation.

The article further vindicates Graham Hancock's complaints of vicious mis-representation. His projections are certainly wrong in myriad details, but he is totally sincere in advancing them. He has predicted, correctly, embarrassingly many recent developments historians laughably insisted were impossible; I would not be surprised at more. When you feel you need to lie about your opponent to discredit him, it tells us more about you than about him.

Genetic evidence, and notions of a more-or-less constant rate of accumulation of mutations, are on much shakier ground than the author suggests. That unreliability is unfortunate for people obliged to rely on it. We can still learn a great deal from it about the order of migrations, but not so much their dates relative to geological events.

Comet strike?

There's a theory that the Younger Dryas was caused by an impact of a bolide on a North American glacier, usually of one that fragmented considerably on entry.

There was certainly a bolide strike roughly coincident with the beginning of the 1300-year Younger Dryas cold spell.

Whether the strike caused the Younger Dryas cold spell is a matter of speculation. We can anyway be confident that the cold spell did not cause the bolide strike.

> There was certainly a bolide strike.

There was not certainly a bolide strike. No one has identified an unambiguous sign of such a strike; a purported impact crater was identified in Greenland a few years ago, but it is not yet confirmed as an impact crater, nor is it well-constrained to occur around the Younger Dryas. (There's apparently a paper suggesting that it's off a tad, maybe 50 million years too early).

The ice core record is unambiguous, corroborated by soil samples from literally dozens of sites as far away as Syria, South Africa, and southern Chile. South African lake sediment identifies an exact year.

The smoking gun is the layer of massively enriched platinum dust without the excess sulfur an eruption would emit, and melt spherules. Anyone doubting a bolide strike needs to account for it all in some other way, a tall order.

A crater would be convenient, but is not necessary: we know about airbursts now. E.g., there is no Tunguska crater. Demanding a crater is not scrupulous.

What's the citation for the ice core stuff? I found two papers that investigated this and neither found evidence to support the impact theory, so it seems ambiguous to me, but this isn't my field so obviously I might just be failing to find a more recent result.

If you wanna read em:

Paquay, François S., et al. “Absence of Geochemical Evidence for an Impact Event at the Bølling-Allerød/Younger Dryas Transition.” Proceedings of the National Academy of Sciences of the United States of America, vol. 106, no. 51, 2009, pp. 21505–10

Surovell, Todd A., et al. “An Independent Evaluation of the Younger Dryas Extraterrestrial Impact Hypothesis.” Proceedings of the National Academy of Sciences of the United States of America, vol. 106, no. 43, 2009, pp. 18155–58.

Update: Found (some?) ice core evidence, it is indeed more recent, but I'm hopelessly out of my wheelhouse at this point so I'll just cite it for anyone also interested and suggest that these more recent publications do seem pretty confident in their conclusion that the impact did happen. So it seems user moloch-hai is correct:

Petaev, Michail I., et al. “Large Pt Anomaly in the Greenland Ice Core Points to a Cataclysm at the Onset of Younger Dryas.” Proceedings of the National Academy of Sciences of the United States of America, vol. 110, no. 32, 2013, pp. 12917–20.

Pretty cool stuff, thanks for sharing and prompting me to learn more about it.

Those are both from 2009, ten years before the smoking gun cited.

They are studiously silent now. [Edit: Thank you for Petaev. I had not seen it.]

> Those are both from 2009, ten years before the smoking gun cited.

Just so you're aware, you haven't actually cited the study yet in this thread.

(Kjær, Kurt H., et al. "A large impact crater beneath Hiawatha Glacier in northwest Greenland." Science advances 4.11 (2018) is the citation, for future reference)

(FWIW, Kenny, Gavin G., et al. "A Late Paleocene age for Greenland’s Hiawatha impact structure." Science advances 8.10 (2022) disputes the age given for that impact crater.)

As already noted, any connection to Hiawatha crater was only ever conjecture. Evidence that Hiawatha was not coincident with the YDB obviously tells us nothing at all about YDB events.

A recent survey article is Sweatman,

The Younger Dryas impact hypothesis: Review of the impact evidence

https://www.sciencedirect.com/science/article/abs/pii/S00128...

The remaining controversy is how much the strike contributed to the Younger Dryas development and other coincident events, particularly extinctions. To me, it is ludicrous to blame those on Clovis people, or on a climate hiccup smaller than they had weathered easily many times before. Now that we know people had already been there for 10+ millennia, the sudden wipeout idea gets much sillier.

The idea that the strike triggered the YD is appealing, but the record shows several other such cooling periods with very similar profile and duration in the past 100ky. It seems unlikely they were all triggered by comet strikes. But they could have been: we now know our records of comet strikes are woefully incomplete, having detected a very recent one only by enormous effort.

See also Wendy S. Wolbach et al.

Extraordinary Biomass-Burning Episode and Impact Winter Triggered by the Younger Dryas Cosmic Impact ∼12,800 Years Ago.

https://www.journals.uchicago.edu/doi/10.1086/695703

Adding: it is disgraceful how sloppy and unscrupulous most opponents of the cosmic impact model have been. They should be ashamed. There is nothing wrong with demanding a high standard of evidence. Failing to maintain even the most basic standards for your own work is, especially in context, inexcusable.

They are righteous defenders of what amounts to the current creation myth of scientism. Nothing to see here when The Science is understood to be a religion.

Wikipedia seems to suggest that evidence for such a bolide strike is disputed. Some claim that the iridium layer, glass sphericals, etc have other explanations.

https://en.wikipedia.org/wiki/Younger_Dryas_impact_hypothesi...

Yes, Wikipedia is notably unreliable in numerous areas. It's supposed to be good for maths, anyway.

Fixing errors and omissions has become difficult.

If wikipedia says something is controversial, then that something is controversial if for no other reason than because there is controversy on wikipedia about it.

This is different than claiming "wikipedia says it's [right/wrong], so it must be [right/wrong]" Demonstrating that an idea is controversial is much easier than proving that idea right or wrong.

Certain individuals are very diligent at scrubbing out whatever they disagree with. The YDIH page is "curated" by a retired professor who insists it lead with a 19th-century speculation, and no doubt will be for a few years more.

Wikipedia "controversies" often carry on for many years after the pros have settled down, until retirees with an axe to grind move on.

Be that as it may, that still makes the subject controversial.

FWIW, I do tend to think the bolide hypothesis seems right. But I wasn't there so I don't really know.

Wikipedia does not define what is controversial. Often it just blows smoke, pretending to fire.

If somebody is blowing smoke about a subject, that's controversy. Controversy doesn't mean "wrong", "debunked" or anything conclusive like that.

Your threshold for "controversy" is way below anybody else's.

Is it controversial whether the Earth is flat? Whether people walked on the moon? Whether they found alien spacecraft there? Whether viruses are involved in AIDS and cancers?

This trivializes the meaning of "controversial" in the context of science, at least, and at the same time places Wikipedia on a level of authority I'm unconvinced is justified. I'm sure there are Wikipedia articles suggesting that climate change is "controversial", too: that doesn't mean it is.

You have it wrong. There is substantial controversy about climate change, but that doesn't mean climate change is wrong (it isn't.)

There isn't any scientific controversy about climate change. There is made-up politically motivated obfuscation in service of certain industries, which is controversial.

The Younger Dryas Impact Event theory - there's some evidence that a disintegrating comet impacted North America ~ 12800 years ago and caused widespread forest fires and the equivalent of a nuclear winter.

Professor Robert Schoch, geologist and writer (2013 book Forgotten Civilization: The Role of Solar Outbursts in Our Past and Future) on this topic has came to the conclusion that it was a Sun outburst which caused this. https://www.robertschoch.com/plasma_iceage.html

Robert Schoch rides his hobby-horse hard. Solar flares and ejections of course occur, and some even hit Earth, but we don't blame them for mass extinctions. (The recent Carrington Event was a small example.) There would be too many mass extinctions.

It's very compelling and I believe it should be researched much more.

For those interested, here is a podcast with Robert where he talks about it. https://youtu.be/uavVGruCUyc

Anything the sun spits out hits, if anything, the entire hemisphere. You don't get to pick out a specific rock for it to melt, but not the next one over.

>People living in southeast Asia 70,000 years ago were certainly sailing out of sight of land, because they reached and colonized Australia. It beggars belief to suggest they did not also go to other places in equally easy reach, and then others from there.

My understanding is that those who reached Australia did not go further, because they forgot how to build ocean-worthy vessels.

There was nowhere further to go, unless you count New Zealand. We don't know if they reached New Zealand. But Australia/New Guinea/Tasmania (called Sahul) was plenty of territory, by itself.

The people who sailed to Australia were of a culture that could sail in any direction, and would have. You would need to come up with a reason for them not to.

And reaching Australia from Asia by island-hopping is much easier than reaching NZ from Australia.

> The article further vindicates Graham Hancock's complaints of vicious mis-representation. His projections are certainly wrong in myriad details, but he is totally sincere in advancing them.

I’ll +1 some of this - the evidence is mounting that standing theories re. the end of the last ice age, impact hypothesis, development of civilization, at the least deserve another look and not quite so much dogma. More underwater archaeology is needed off the coasts, and under the Amazon and probably Sahara. These are all tough places to investigate but who knows, maybe we need to push our civilizational history back a few thousand years.

Graham really can’t clutch his pearls too much though. His early stuff was just kooky and he still has a tendency to weave way too much of the metaphysical and flat-out conjecture into his ideas. It turns academics off (putting it mildly), exactly the people who’s credibility and attention he craves. It’s tough for me to tell when Graham has actually done some interesting research and is calling out something real vs Graham when he’s nine oh-what-if-they? levels deep into conjecture.

If Graham would put his head down, eat a great big ice cream scoop of skepticism chocolate, and then go do investigative work and let the facts lead him - full stop - he’d probably make a ton more progress with his ideas than he has.

Hancock is equipped neither by training nor temperament to be a scientist. He does not pretend to be one. Trying, he would fail. Judging him as one is deeply silly. He calls himself a journalist. He is a storyteller, and invents engaging stories.

What he attempts is very different from science. He openly speculates about where the evidence might lead. His failure to understand some of the evidence, and what is possible, sometimes leads him to howlers. But remarkably often he has predicted finds that historians foolishly insisted were impossible.

His appeal is in actually engaging with evidence historians and archaeologists try to conceal or downplay. He takes us to actual sites, and shows us evidence historians refuse to discuss, or as often openly lie about. His speculations are fluff. But taking us around to see things, and inviting us to speculate along with him, is engaging in ways nothing allowed to scientists can.

Scientists could draw huge benefit from engaging with the evidence he exposes, instead of demonizing him. Their complaints fall flat because he is, simply, not a scientist, even a bad one, and should not be treated like one. He inspires with what might be, which is a good thing, and that he would do better with better help.

(Uniquely, Scientists Against Myths, on YT, does more engagement than anybody else, but in a way that is badly off-putting. They forget that they are addressing the audience, not their perceived myth-maker enemies.)

He would still be often wrong, but more interestingly wrong. And sometimes, still, he would turn out to be right. There is nothing wrong with that.

There is I think a little bit of chronological confusion that I will try to clear up. My understanding of the consensus rough chronology is as follows:

* Populations move into Beringia maybe 20-25kya. (My knowledge of this date is particularly hazy).

* Populations start moving from Beringia into the Americas. This date is highly contested, but it's accepted that this occurred at least 15kya.

* Clovis culture starts up around 13kya, ends around 11.5kya.

* Younger Dryas starts up 12.8kya, ends around 11.5kya.

So genetic evidence suggesting that peopling starts from around 17kya isn't inconsistent with mainstream dates for peopling of Americas, although it would mean being suspicious of sites much older than 17kya.

> but the really interesting question from here then is who were they and what happened to them?

My interpretation of the evidence... they became Clovis culture.

The lakebed footprints securely scotch that timeline, and Cerutti blasts it to smithereens. The most that could be left of it is that these late migrations somehow wholly supplanted earlier populations.

Either the earlier pop. died out before the later crew arrived, or ... well, genocide is a demonstrated human behavior. It is hard to carry out continent-wide without microbial assistance, but they could have had that.

It’s cool to be excited about this - who wouldn’t be? - but you’re using very definitive language for highly speculative. The article outlines a timeline which, as with the post you’re replying to, is compatible with the White Sands lake footprints.

The Cerutti site _could_ completely upset that theory but it’s far from proven that it’s not a misunderstanding, or that it was Homo sapiens and not another hominid. That would be exciting in its own right, but until there’s more confirmation we should be careful not to describe these as facts or highly-probable.

There seems no possibility of an upset to Cerutti. Bone fragments in the rock faces, greenstick fracturing, adjacent placement of stones and hip-joint ends.

The only plausible complaint I have heard of is lack of stone-knife flakes, but the site is still being excavated.

That it might have been H. e. is exciting. They did get around!

Yes, multiple waves is suggested near the very end of the article, and that this is a focus of current data collection:

> Another possibility ties together evidence of Population Y and potential archaeological evidence at sites like White Sands. Could there have been multiple migrations into the Americas, with one pre-LGM migration consisting of Population Y individuals (and perhaps Unsampled Population A or other groups we have yet to identify), and one post-LGM migration? This would reconcile the archaeological evidence of early traces of humans in the Americas (if they are indeed legitimate, which has yet to be demonstrated to everyone’s satisfaction) and the genetic data.

> Archaeologists sceptical of White Sands’ early dates are dubious of the second scenario, and it is admittedly speculative. We need a great deal more data, both genomic and archaeological, to test it. But, as a field, we are actively engaged in collecting that data, even as I type these words.

The 16-17ka date is the divergence between Northern and southern native american groups, both related to the later (~13ka) clovis culture. Indigenous americans as a whole diverged from Eurasians sometime before 20ka. That initial population eventually split into multiple lineages (Unsampled Population A, Ancient Beringians, Clovis ancestors) that entered the Americas, although it's not clear what order those events occurred in.

We know that there was also later admixture between Alaskan and Eurasian populations across the bering strait and groups like the paleoinuit likely originated (partially) on the siberian side of the straight, but the vast majority of indigenous ancestry across the Americas as a whole derives to the ancestors of the clovis complex. It's not clear how preclovis people relate genetically to those clovis ancestors in the absence of genetic data for them.

There were multiple out of Africa waves, and this seems like the simplest plausible explanation. Occam.

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