A Sea of Younger Dryas Woo

by Brian Dunning
July 16, 2024

The Younger Dryas event, a 1200-year period of unusual cooling at the end of the last ice age, is said by some to have been inexplicable according to conventional climatology. And so, some believe, it must have had an exotic cause, perhaps a barrage of meteors that wrapped the Earth in a shadowy blanket of cold. They believe this period was so uniquely destructive that it could only have been the cause for the destruction of Atlantis. Today we're going to find out whether this is what scientists and historians believe, or whether it's the realm of — well, other types of thinkers.

First, a brief explanation of what the Younger Dryas period was, as it very much was a real thing. The most recent ice age, often called the Last Glacial Period, is generally considered to have lasted from 115,000 years ago until 11,700 years ago. That's a long time, and during the ice age there were a lot of minor climatic events where it would get a little warmer or a little cooler for a few centuries — in all, climatologists have identified about 25 major climatic events since the start of the ice age, with rapid beginnings and endings on the order of decades or centuries. But about 18,000 years ago, temperatures began trending upward for good, signaling a final end to the ice age. It warmed and it warmed; but then, about 12,900 years ago, that warming paused and we had another twelve cooler centuries, which lasted until 11,700 years ago, when the warming resumed. Those twelve cooler centuries during the overall warming are what's called the Younger Dryas event. Then, by eight or nine thousand years ago, temperatures got close to where they remained until this past century.

So that's the Younger Dryas period in a nutshell. Its end is what we consider the official end of the ice age, and the beginning of the Holocene epoch. The ending of an ice age was a major climate event that also brought the extinction of many famous species of prehistoric megafauna — giant sloths, short-faced bears, woolly mammoths and mastodons, saber-toothed cats, dire wolves — in all, about 70% of all the world's species of megafauna failed to survive the warming end of the Pleistocene.

But we should also be clear that while Younger Dryas was a period of cooler temperatures, these were only in the northern hemisphere. The southern hemisphere, conversely, was warmer during that same period. It was a complex event, as were all such events. So it's best to think of Younger Dryas as a climate disruption, rather than strictly as a cooler period.

So this is all pretty cut and dried science. We have huge amounts of evidence for the Younger Dryas period, as we have for all of those 25 or so climate events since the beginning of the ice age. We have ice core data. We have lake and marine sediments. Pollen. Speleothems. Glacial geology. Marine microfossils. Dendrochronology, and more. So you might be wondering if the science is this solid, where is there room for any woo (more properly called, in this case, misinformation)?

Nearly all of it comes from the world of pseudoarchaeology. Pseudoarchaeology is the decidedly unscientific field in which people with little or no education in real archaeology come up with alternate Earth histories based upon their own notions, or upon YouTube videos made by people who prognosticated the content from their own notions. Consequently, these ideas are generally in direct opposition to knowledge held by the people who actually are archaeologists and have learned the field and done the work. The basic plot is that the Younger Dryas is believed to have been so uniquely catastrophic that it caused a global cataclysm, destroying ancient civilizations like Atlantis and wiping out all manner of advanced peoples who lived here before us. And thus, as a sudden global catastrophe, it must have had a sudden trigger, like a worldwide barrage of meteors or massive supervolcanoes or an explosion of radiation from the sun or deep space.

We'll talk about some of these alternative conjectures in a moment, but one thing that's important to note is they all treat the Younger Dryas as if it was a unique event requiring some kind of exotic explanation. It was not unique, or even very different from many other similar events. For example, the two similar cool periods before it were the Older Dryas and the Oldest Dryas, these were only the most recent of all these 25 or so such events. (Incidentally, the Dryas periods get their name from the eight-petaled dryad flower, because sediments from that era are rich with dryad fossils.)

We'll get started on our alternate theories of Younger Dryas with the one that's best to have as a foundation, and that's the real science:

The real cause

Cooling periods during the past ice age, including the three Dryas events, all have a lot in common. The most significant of these has to do with a major Atlantic current called the AMOC, the Atlantic Meridional Overturning Circulation. This is the most important current in the Atlantic. Think of it as a great underwater conveyor belt, its top layer moving northward, bringing warm southern waters into the northern hemisphere; and its bottom layer making the return trip, moving the deep, colder, saltier water southward. This deeper southward current is called the NADW (North Atlantic Deep Water) and it collects cold water from a complex of several northern currents. The AMOC is hugely influential on climate.

When the AMOC weakens, less heat is brought from the south to the north. The north cools, the south warms. This is exactly what happened during the Dryas periods and other cooling periods before them. Scientific support for the weakening of the AMOC as the primary cause of the Younger Dryas and other such periods is practically universal. But where opinion spreads out a bit is on the triggering events that caused the weakening. Here's where we come to a very important point: the fact that there are differing opinions on the triggering events doesn't mean nobody has a clue and the alternative conjectures are equally likely. It means the trigger was multifactorial and it's very hard to know how much influence each of the factors had. Scientists almost all agree on what the primary triggers were. They are:

1. An enormous influx of freshwater into the North Atlantic, from the collapse of ice dams in North America.
2. Complex feedback mechanisms worldwide, combining things like reflectivity from snow cover and the impacts of sea ice and vegetation.
3. Extreme volcanic activity could add cooling dust into the atmosphere.
4. The fierce complexity of global climate and how massive scale patterns interact with one another.

Between those, we're covered. We know those triggers all happened to some degree, and between them they are sufficient to explain the cooling periods. But nobody has a complete picture of exactly how influential each was during each cooling period, and that's basically the scope of the uncertainty that exists.

And so, seizing upon that uncertainty and magnifying it into a straw man that nobody knows anything and therefore any random conjecture is equally valid, alternative historians of all stripes have proposed these bizarro world scenarios:

Younger Dryas destroyed Atlantis/Lemuria/etc.

We've talked about both Atlantis and Lemuria in previous Skeptoid episodes, and obviously, neither actually existed and so of course was unharmed by Younger Dryas. But pseudoarchaeology authors like Graham Hancock and Andrew Collins continue to make this claim. In the episode on the Göbekli Tepe archaeological site in Turkey, we discussed how both authors (via different mechanisms) credited Younger Dryas with the destruction of Earth's earlier advanced civilization, prompting the few dumb human survivors to build a megalithic structure.

This is also often raised in the context of something being found that seems strange, like an out-of-place artifact, that could be a relic of lost advanced technology from some ancient race. Hancock makes this claim explicitly about Göbekli Tepe, falsely asserting that its layout or measurements are too precise for mere humans.

Such alternative historians fail to convincingly explain why the Younger Dryas would have had such a catastrophic impact on their advanced ancient civilizations, when they seem to have weathered all the earlier similar periods without a problem.

Younger Dryas was caused by a barrage of comets or meteors

It's called the Younger Dryas impact hypothesis, and it's what both Hancock and Collins believe happened. The idea of large impacts about that time in Earth's history does have a small amount of academic support, but as the evidence is scarce, it remains a fringe idea; and there's almost no support for the pseudoscientific belief that such impacts could have a 1200-year effect. It's also not clear why Hancock, et al. feel that only the Younger Dryas event required such an exotic trigger, since they don't seem to have any issue with the science-based explanations for all the other events.

Younger Dryas was caused by extreme solar activity

Most famously espoused by geologist Robert Schoch, who keeps one foot in the world of real science and the other firmly in pseudoscience, this idea is that an intense solar event like solar flares or coronal mass ejections triggered Younger Dryas. Now, it is true that the most extreme of such events can have minor influences on weather, there's no underlying theory for how it could possibly cause such a fundamental 1200-year shift in Earth's climate. Schoch does not propose this for the other Dryas periods or the preceding cooling periods, only Younger Dryas; which seems odd.

Younger Dryas was God's tool for creating the Flood

Graham Hancock is also among a number of authors who have proposed that massive flooding during the Younger Dryas period was a likely cause for the Biblical Flood; if not literally, then at least those floods could be the source of stories that later made it into the Bible. The only problem with this is that there is no reason to think Younger Dryas would have caused floods in the Holy Land or anywhere in its vicinity.

Younger Dryas brought about a profound change in human consciousness

The overall shift in temperatures from the ice age to the Holocene took about 10,000 years, during which humans had ample time to gradually migrate as they saw fit. And of course they lost much of whatever megafauna they may have hunted, so there were also gradual changes to their diet. But to characterize this as some kind of profound, cosmic shift in consciousness is hard to defend. Yet you'll find it in the writings of Hancock, Schoch, Rand Flem-Ath, and others.

To me, Younger Dryas is the perfect candidate for a topic that draws pseudoscience like flies. Pseudoscientists like Graham Hancock know that it has a sciencey-sounding name, so invoking it adds credibility to whatever wild conjecture he's pitching that day; he knows few people have any idea what it is or how it worked, so he can pretty much say whatever he likes; and yet it's a real thing that has real scientific evidence behind it, so any fact checking tends to lend him even more unearned credibility.

And that, my friends, is why we will probably always have currents of pseudoscience running through a sea of Younger Dryas woo.

By Brian Dunning
Follow @BrianDunning