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Around 50,000 years ago, Mandrin Cave was a lonely place.
Hollowed out of a limestone cliff, the cave overlooked the Rhône Valley in southern France. The valley, now a lush, rolling landscape of vineyards and orchards, was then cold and bleak.
A small band of Neanderthals, numbering no more than 30, eked out a harsh life in Mandrin Cave.
They were an isolated group. So isolated that it might be hard for us sapiens to imagine.
Genetic evidence tells us that it had been about 55,000 years since they’d had children with Neanderthals from other communities.
55,000 years! For all that time, they’d had children only with each other. Now they were one big family. Inbreeding had stripped away their genetic diversity. It had left them painfully vulnerable to harmful genetic mutations. It had made it easier to get sick, and harder to have children.
Life was difficult in other ways. The skeleton of one Neanderthal man recovered in Mandrin Cave suggests a life of grueling work.
The man’s front teeth are thoroughly worn, indicating that they were used as tools for gripping and pulling hides, for example. Enlarged fingertips and the bent of his thumb hint at repetitive, strenuous labor with simple tools.
In the frigid but unstable world of the late Pleistocene, small Neanderthal groups survived for timespans that may be hard for us to fathom. Somehow, for thousands of years, they endured, teetering on the edge of disaster.
But in the end, the Pleistocene may have been too much to handle.
The community at Mandrin Cave struggled on for at most 8,000 more years. By around 40,000 years ago, every last Neanderthal was gone.
Welcome back to The Climate Chronicles. In this episode, we’ll explore what could be the ultimate climate change disaster.
We’ll consider the extinction of intelligent, sapient life on Earth – our species excepted, of course.
We’ll focus on Neanderthals. Other than sapiens, Neanderthals may have been the most intelligent creatures in the history of life on Earth. Their behaviors, their cultures, in some respects resembled our own.
Yet unlike us, they didn’t escape the Pleistocene.
In this episode, we’ll sift through diverse evidence, from computer models to ancient DNA, to see if we can’t pin down an explanation for the disappearance of humanity’s Neanderthal cousins.
We’ll investigate whether Neanderthal communities disappeared for the same reasons that seem to have doomed other megafauna – a combination of human hunters and climate change.
We’ll try to figure out how these threats, and others, may have snuffed out one group of Neanderthals after another.
And we’ll consider how much of an advantage intelligence really confers in the struggle for life on a changing planet.
Big histories – interdisciplinary accounts of the past that tell the human story on the grandest possible scale – are usually stories of emergence and expansion.
Hominins evolve, they learn new things, they begin to control their environments, and finally the smartest hominin – sapiens – puts everything together. Agriculture, cities, empires, writing, science, industry: every breakthrough unfolds in a grand narrative of progress. If you’ve ever played the videogame Civilization, you’ll know what I’m talking about.
There are exceptions. Sapiens, a bestselling book written by Yuval Noah Harari, portrays agriculture as a disaster that, for millennia, worsened lives for most people. The Dawn of Everything, an anarchist reimagining of history by David Graeber and David Wengrow, views the emergence of the hierarchical state as the real regression.
Both books cherry pick historical case studies to attempt to revise our understanding of the past. Both, however, ultimately focus on the growth and development of humanity. And until this episode, it’s fair to say that our podcast has done the same thing.
It’s just hard not to when the dominant trend line of our species has pointed up. Since the late Pleistocene, the global sapien population has steadily grown larger and more connected. Now, of course, we dominate the Earth.
But the hominin story writ large is overwhelmingly one of failure.
Every hominin species except ours went extinct. No hominin species has survived even as long as the average animal species. And every hominin species but ours seems to have had a pathetically small population alive at any one time – smaller than that of many other big predatory mammals.
For example, coyotes and Homo erectus both evolved around two million years ago. Yet the coyote population always seems to have been at least ten times bigger than that of the erectus population.
So why was the coyote, of all animals, apparently more successful than one of the most adaptive, ingenious creatures in the history of life on our planet?
The answer is simple: big brains have a lot of disadvantages.
First, they require enormous amounts of energy to run. Just think of how much harder it is to keep a supercomputer going than a digital watch. A big-brained animal needs a lot of good, nutritious food, every day, or it’ll die.
It was hard for hominin populations to grow very big, because it was hard for nomadic or semi-nomadic gatherers and hunters to find enough food to sustain large populations in most Pleistocene ecosystems.
What’s more, because big brains require a lot of protein, some hominin groups hunted very big and dangerous animals. Many Neanderthals in Europe, for example, obtained much of their protein by ambushing giant beasts with spears.
Battered Neanderthal skeletons reveal that they routinely suffered traumatic injuries in these encounters, and not all of them survived. Osteology – the study of bones – therefore reveals a second limit to hominin population size: the danger of obtaining enough fuel for big brains.
Those brains obviously need big skulls. But bipedalism, which might have encouraged brain growth by freeing up hands for tool use, limited the size of hominin pelvises.
It was hard for babies with big brains to fit through hominin birth canals. You probably already know that human babies actually have to rotate during birth.
The upshot is that childbirth was much riskier for hominins than it was for other species. In the era before modern medicine, many women died in childbirth. Many babies died, too. That imposed a third limit to population size.
Hominin babies also took a long time to grow up. That goes back to those small birth canals. The brain of a human infant is big compared to that of other baby animals, but it’s as small as possible for how big it’ll become.
Babies and young children are helpless – my five-year-old has an accident every week, so I know from experience – and sadly, that also constrained population sizes in hominins. Families were vulnerable, and many children died. A fourth limit.
Given these colossal disadvantages, there really had to be a powerful return on the big brain investment for hominins to survive in the first place, let alone to thrive.
The advantages of great intelligence – including the capacity to adapt to climate change – only barely outweighed the disadvantages in every hominin species until we sapiens had our cognitive leaps and cultural transitions in the late Pleistocene.
This all goes back to that first possibility I mentioned in the conclusion of episode six, our season 1 finale.
Admittedly, measuring intelligence is extremely hard. Even ranking intelligence in humans turns out to be nearly impossible. It’s that much harder to compare the intelligence of whole species.
But given this caveat, I think we can speculate, based on the hominin histories we’ve already explored, that very high levels of intelligence might not be as effective an adaptation to environmental change as it may seem.
It may be that only when intelligence crossed a very high threshold did it become a uniquely powerful evolutionary adaptation. Only then did it unlock the capacity for cultural transformations that could begin to loosen some of the limits on hominin population size.
It’s plausible – though, as we’ll see, by no means certain – that only sapiens ever reached that threshold. And it certainly appears that there was nothing inevitable about the emergence of a hominin that could get there. Given the small and precarious populations of our hominin ancestors, the evolution of intelligence on our planet could easily have stopped in its tracks before we ever showed up.
Even now, there may be something maladaptive about our intelligence. Today, it seems distressingly possible that we’ll end up destroying ourselves. It appears that we’re constantly finding new ways to do it.
If we pull it off, then big brains really are an evolutionary dead end.
As I prepared this episode, researchers published a brand-new study that evaluated changes over time in the diversity of the bony labyrinth – meaning, the inner ear structure – of late Pleistocene Neanderthals.
This strikes me as a really cool example of the creative detective work with which we can illuminate previously hidden aspects of the past. That’s because little differences in the bony labyrinth between individuals appear to reveal that a hominin species is genetically diverse. And genetic diversity is a strong indicator of population size.
So, it seems that when Neanderthal inner ears had a lot of variation, the total global Neanderthal population was relatively big, but when inner ears grew less diverse, then the population had declined. Ancient DNA could also reveal these trends, but geneticists haven’t yet uncovered a lot of Neanderthal DNA that’s more than 100,000 years old.
Ears, of all things, appear to tell us that the Neanderthal population was not stable over time. In particular, it seems to have grown around 130,000 years ago, then collapsed some 10,000 years later. You may remember that this period coincides with the Eemian interglacial, a warm, wet, but relatively short stretch of the Pleistocene that preceded the epoch’s final glacial cycle.
The Eemian ended around 115,000 years ago. Thereafter, global temperatures generally cooled, ecosystems dried up, ice sheets expanded dramatically, and sea levels plummeted.
It’s tempting to conclude that Neanderthal communities across Eurasia boomed when warmer, wetter conditions nourished more diverse and productive ecosystems. Forests expanded, for example, replacing barren tundra at high latitudes, while inhospitable deserts transitioned into watery grasslands.
It’s hard to pin down an exact number, but it seems reasonable to conclude that in this golden age, the global population of Neanderthals reached about 250,000.
For millennia, Neanderthals had plenty of animals to hunt. But renewed cooling and drying destroyed or fragmented the ecosystems that had sustained large Neanderthal populations.
Many communities disappeared, or retreated into environments that remained habitable: refugia in the Caucasus, for example, between the Black and Caspian Seas, or Iberia – or southern France.
Neanderthal communities, such as the one in Mandrin Cave, were increasingly isolated from one another. Inbreeding grew more common. Genetic diversity slumped.
Of course, as we discussed in our last episode, it’s hard to prove that climate changes caused such shifts in population size and distribution. Once again, researchers have a correlation, they have a probable mechanism to explain the correlation, but they can’t definitively establish causation.
Obviously, they can’t travel back in time to observe whether cooling and drying trends forced Neanderthals to migrate away from advancing ice sheets and deserts.
We should therefore admit that climate changes might not have been responsible for the rise and fall of Neanderthal populations around 130,000 years ago. We don’t know for sure, because we fundamentally can’t know for sure.
With that said, the bigger or more abrupt the climate change, the more direct and profound its impact was likely to be on human, and hominin, populations.
Now, as I say these words, the world has warmed by almost one and a half degree Celsius, on average, since the late nineteenth century. Our best bet is that it’ll warm at least one more degree by the end of this century.
A total warming of two and a half or – God forbid – three degrees Celsius, relative to that late nineteenth-century average, will create a new, and for humans, much less habitable Earth.
That’s because, although these variations in temperature may seem small, their impacts are vast. One reason is that they exponentially increase the likelihood of extreme weather events.
Climate models simulate that a world three degrees Celsius hotter than it was in the late nineteenth century is also a world in which deadly, once-a-decade heatwaves are nearly fourteen times more likely to occur.
So, imagine. In the 100,000 or so years from the height of the Eemian to the nadir of the Last Glacial Maximum, Earth’s average temperature cooled by perhaps eight degrees Celsius in total.
At high latitudes – in the far north and south – the temperature swing may have been around 20 degrees Celsius! And as we’ve seen, the decline happened in fits and starts, making it harder for Neanderthals and other hominins to adjust.
Yes, it’s true that we should be cautious about assuming causation based on correlations and hypothetical mechanisms. But at the same time, we should acknowledge that when climate changes are big enough, and mechanisms are clear enough, then climate can become far and away the most likely explanation for a historical change.
That certainly seems to be the case for the collapse of the world’s Neanderthal population during the early stages of the Last Glacial Period.
After the collapse, Neanderthals never recovered. In fact, quite the opposite. Diverse evidence, including ancient DNA, tells us that although the Neanderthal population decline slowed for a while, it continued.
Then, beginning around 70,000 years ago, Neanderthal populations seem to have plummeted again, with the onset of an even colder, drier phase of the Last Glacial Period. Small Neanderthal groups retreated further into shrinking refugia, and became even more isolated.
By about 50,000 years ago, when we met our group in Mandrin Cave, Neanderthals were in truly dire straits. The population of the species might have declined by about two-thirds or even three-quarters since its peak in the Eemian, some 80,000 years earlier.
Now, perhaps 70,000 Neanderthals remained. Lonely, inbred bands of about twenty to thirty individuals were scattered across a huge territory from western Europe to central Asia. Imagine the population of an ordinary town sprinkled over a continent, and you’ll get a sense of just how isolated these little bands were.
Still, the species was far from doomed. Today, the total population of Nile crocodiles is also about 70,000, but the species is classified as being of “least concern,” meaning it’s in no danger of extinction.
The Neanderthals, by contrast, only had about 10,000 years left to live. Why did they disappear? Did it all come down to one final spasm of Pleistocene climate change?
Or was there something else at work?
What was a Neanderthal?
We’ve talked about their bodies, their brains, and their population. But what was it like to be a Neanderthal? How did Neanderthals think? Did they have a culture, or perhaps many cultures?
Of course, the common stereotype is that they were lumbering, ape-like brutes, clumsy and obviously less developed than sapiens. If you want to insult somebody’s intelligence, you might call them a Neanderthal.
That stereotype actually has more to do with human than Neanderthal stupidity.
Paleoanthropologists, who focus on the study of hominin remains, and archaeologists, who concentrate on artifacts, now understand that the cognitive abilities of Neanderthals were actually remarkably similar to our own. Recent discoveries have established that Neanderthals self-medicated with plants; cooked and mixed complex adhesives to forge multi-part tools; and twisted fibers into cords and ropes.
Neanderthals also seem to have cared for one another. Recently, researchers extracted a 50,000-year-old Neanderthal skeleton from a cave in Iraqi Kurdistan. Analysis of the battered skeleton revealed this Neanderthal must have been partly blind from a crushing skull injury. He had a withered and amputated right arm, a crippled leg, and bone growths that must have made it all but impossible for him to hear. Still, he lived into old age – his 40s – with what must have been a lot of help from his friends.
Neanderthal remains found in shallow depressions moreover suggest that Neanderthals buried their dead. Pollen found with one body – again from that cave in Iraq – may even provide evidence of a burial, hinting at spiritual beliefs among at least one Neanderthal population that were previously thought to be unique to sapiens.
Collectively, these remarkable new glimpses of Neanderthal intelligence are one reason that some scientists view Neanderthals as a subspecies of Homo sapiens. It does seem that Neanderthal brains were wired more for visual processing at the expense of social memory – but as we’ve discussed, those brains might have been bigger, on average, than ours.
It’s entirely reasonable to conclude that the cognitive abilities of Neanderthals were similar to our own.
In my view, however, there’s still plenty of evidence that sapiens had subtle but, collectively, decisive advantages over Neanderthals. For example, it doesn’t seem like Neanderthal populations quite matched the pace of technological and social innovations that were beginning to sweep through sapien groups by about 100,000 years ago.
It’s also hard to deny that sapien communities were more interconnected, more networked, and overall larger than those of Neanderthals, which may may have aided the invention and spread of new ideas. And again, neurons in those sapien brains were denser in the frontal cortex than they were in Neanderthal brains, which may have given sapiens an edge in creativity and social cognition.
Most importantly, the sapiens spread across the world, including huge regions never inhabited by Neanderthals, just as the Neanderthals retreated. And where both species came into contact, Neanderthals eventually disappeared.
Could it be that networked sapien communities were more resilient in the face of climate change than isolated Neanderthal bands? Is that why sapiens thrived as Neanderthals withered away?
Well, in the critical period between about 45,000 and 40,000 years ago, when the last Neanderthal communities disappeared, isotopes in ice cores tell us that Dansgaard–Oeschger events repeatedly and abruptly warmed, then cooled, climates across huge stretches of the northern hemisphere.
At high latitudes, as we’ve seen, these climatic shocks could warm or cool climates by more than ten degrees Celsius in just a few decades!
So, at first glance, it does seem like Neanderthals went extinct during an extraordinary period of climate volatility that sapiens were, apparently, better equipped to handle.
Remember, however, that Neanderthals had already retreated into refugia: regional environments that had remained stable and habitable when hemispheric or global climates changed. Scientists have studied stalagmites, the rocky formations in caves that look like upside-down icicles, and used their isotopes to establish that precipitation in Neanderthal refugia around the Mediterranean probably didn’t change much during D-O events.
It seems that climate change can help us understand why Neanderthals had been pushed to the fringes of the vast territories they once occupied. It can probably help us explain why the overall Neanderthal population was much lower than it had been, and why Neanderthal communities were increasingly isolated from one another.
In other words, climate change seems to explain why Neanderthals had grown more vulnerable to further decline. Vulnerability is a key word in climate change scholarship. So is risk. In the case of the Neanderthals, vulnerability increased the risk that something horrible would happen – such as extinction.
But climate change doesn’t seem to have been a direct cause of the disappearance of Neanderthals around 40,000 years ago. Again, climate probably set the stage for that disappearance, but didn’t itself make it happen.
Something else must have delivered the killing blow.
In our last episode, we saw that sapien migration out of Africa – and at times, back into Africa – really took off by around 65,000 years ago.
Eventually, sapien settlers arrived in Neanderthal refugia. After all, these were some of the best places left to hunt big animals – and to gather seeds, fruits, nuts, tubers, and other structures that plants used to store starches, fats, and protein.
In Europe, sapiens appear to have rubbed shoulders with Neanderthals for a few thousand years, at most, before Neanderthals went extinct. When you consider the vast timeframes of the Pleistocene, a few millennia seem like the blink of an eye.
From one perspective there is, therefore, a suspicious correlation between the arrival of sapiens and the disappearance of Neanderthals. We might even lump Neanderthals in with other predatory megafauna that disappeared when sapiens hunted too many big herbivores.
Now, several years ago, researchers ran a supercomputer simulation to reconstruct what might have happened when sapien settlers arrived in Neanderthal hunting grounds. The simulation accounted for all the information that archaeologists, geneticists, paleoanthropologists, and paleoclimatologists have accumulated about hominin behavior and regional environmental conditions.
The simulation suggested that the only realistic explanation for the extinction of Neanderthals was a decisive disadvantage, relative to the sapien newcomers.
It may be that the sapiens were better hunters, owing perhaps to superior intelligence. Archaeologists have uncovered evidence that, in Europe, early sapien settlers used bows and arrows, a projectile weapon that Neanderthals apparently hadn’t invented. Technology therefore could have allowed sapiens to kill more animals, more safely, than their Neanderthal competitors.
In any case, the computer simulation suggests that sapiens multiplied more quickly than Neanderthals, and consumed the animals that Neanderthals had hunted. If that was indeed the case, Neanderthals really were just another megafaunal predator that had been stressed by climate change when sapiens overhunted its prey, and doomed it to extinction.
Other computer models, however, seem to tell us that this picture is a bit too simplistic. They indicate that when sapien settlers arrived, Neanderthals quickly disappeared only from ecosystems in which the animals they’d hunted were rare, or in which the number of those animals fluctuated a lot from year to year.
That’s one problem with computer models that simulate hominin behavior. It’s hard – perhaps impossible – to plug in and properly weigh every factor that mattered for past environments and peoples. That’s partly why different models can tell us different things. And we probably still don’t know about some factors.
In any case, more productive ecosystems with larger and more dependable animal populations permitted longer coexistence. And here we should remember that a few thousand years is a really long time to live side-by-side.
Entire millennia can seem like the blink of an eye when we zoom out to consider vast timescales, which we often do in Pleistocene research. But things that happen in the same millennium are not necessarily related.
After all, my decision to make The Climate Chronicles didn’t have much to do with the Norman conquest of England, about a thousand years ago.
Explanations for the Neanderthal extinction that help explain the lag between the arrival of sapiens and the disappearance of Neanderthals can therefore be especially intriguing. And once again, we can use models – imperfect though they may be – to test different possibilities.
Now, it seems that Neanderthal and sapien populations evolved separately for tens, perhaps hundreds of thousands of years. In that time, each population would have co-evolved with a different collection of bacteria, viruses, and parasites.
It may be that, when sapien groups left Africa around 130,000 years ago, at the start of the Eemian, they encountered fairly large Neanderthal populations with unfamiliar diseases, diseases to which sapiens had no immunity or resistance. Neanderthals meanwhile found that sapiens had diseases that they hadn’t seen before.
The mutual “disease burden,” as it’s called, created a kind of stalemate. Too many sapiens died for them to press deeper into Neanderthal territory. And the sapien migration fizzled.
By the time the big wave of sapien migrants left Africa about 70,000 years later, however, Neanderthals had retreated into their refugia. When sapiens finally rubbed shoulders with them in Europe, around 42,000 years ago, genetic evidence reveals that some sapiens had children with Neanderthals.
It may be that this interbreeding helped break the stalemate. Now, both populations exchanged protective immune alleles – genes involved in the immune system. Over time, sapiens developed immunity to Neanderthal diseases.
But there were more sapiens, and they came from tropical environments teeming with animal species that act as reservoirs for pathogens – the microorganisms that cause disease. Sapiens may have had more diseases, and Neanderthals, being less genetically diverse, had less capable immune systems.
The result may have been that sapiens were now more protected from Neanderthal diseases than Neanderthals were protected from sapien diseases. And perhaps the alleles that sapiens had acquired from Neanderthals kept disease from interfering with other sapien advantages, such as a superior ability to hunt.
So, sapiens flourished, while Neanderthals went extinct.
It’s a strange and striking possibility. If the story is true, it that bears some resemblance to what happened 40,000 years later, between the fifteenth and eighteenth centuries, when European settlers arrived in environments previously isolated from Eurasia and Africa. We’ll cover the genocide that followed, and its possible climatic repercussions, in a later episode.
The story also suggests that it was acts of interspecies lust – or love – that unleashed the big forces responsible for driving an intelligent species to extinction.
Imagine a Pleistocene Romeo and Juliet . . . on an epic scale.
I like the disease doom story, but there isn’t a lot of proof for it. The real cause for the disappearance of our Neanderthal cousins may have been much more mundane.
Now, one thing I’ve slowly come to appreciate while working on climate is the extent to which things can change with no external – or, to use another word, exogenous – intervention.
Complex systems can really have a life of their own. A million random fluctuations so small as to escape notice can together interact in ways that cause profound change, or even collapse.
Climate, for example, tends to undergo random variations with no external forcing, such as a volcanic eruption or a polluting primate.
And animal populations can also fluctuate of their own accord.
Yet another study using computer models found that inbreeding in tiny, isolated populations would have eventually hobbled the reproductive fitness of Neanderthals as a whole. With the overall Neanderthal population already very low, it got harder and harder to have kids.
Meanwhile, each Neanderthal community was ultimately so small and alone that random demographic variations – the loss of a few hunters to an angry mammoth, for example, or the loss of several mothers in childbirth – could have doomed that community.
Models simulate that these realities were together sufficient to lead Neanderthals to extinction. If sapien settlers contributed at all, it might have been in subtle ways – by further fragmenting and isolating Neanderthal populations, for instance, worsening the inbreeding that lowered reproductive fitness.
If this theory is right, then from one perspective there was nothing particularly remarkable about the disappearance of Neanderthals. Once the Neanderthal population grew sufficiently small and fragmented, extinction was always the most likely outcome.
But from another perspective, the theory, if correct, would mean that climate change probably did destroy the Neanderthals.
After about 115,000 years ago, a population collapse, likely driven by climatic cooling and drying, meant that Neanderthals were a dead species walking. It took millennia before they disappeared, but in a frigid, unstable climate, the final decline was all but inevitable after the collapse.
Of course, the other explanations for the final disappearance of our Neanderthal cousins also involve climate change – albeit indirectly. After all, it seems that the sapiens who hunted more effectively or carried deadlier diseases would never have reached Neanderthal refugia without climate changes that broke the desert barriers surrounding Africa.
In all likelihood, the extinction of the smartest hominin that ever lived – with the possible exception of ourselves – was probably multicausal. It probably involved a combination of the pressures we’ve discussed.
But in any scenario, the most important influence was probably climate change.
In a way, Neanderthals live on.
If your distant ancestors migrated out of Africa after about 65,000 years ago, one to four percent of your genetic code is actually Neanderthal.
Your body may therefore preserve something of the legacy, the identity, of the last truly intelligent species with which we shared our planet.
If you have them, Neanderthal genes probably strengthen your immune system. They may bolster your defenses against RNA viruses, such as West Nile and hepatitis C.
But a stronger immune system can also raise our susceptibility to autoimmune disorders. Neanderthal genes makes us more vulnerable to Crohn’s Disease and Lupus, for example.
Neanderthal genes also seem to fortify our skin and hair for life in cold climates. They helps us store fat, a helpful adaptation in frigid environments, but a contributor to type 2 diabetes today.
Similarly, Neanderthal genes may alter our pain sensitivity and help our blood clot – again, useful adaptations to a harsh Pleistocene life, but today a source of increased risk of heart disease.
It even seems that Neanderthal genes are correlated with much higher susceptibility to severe COVID-19 symptoms, and perhaps a slightly increased risk of depression and anxiety.
An echo, maybe, of the last days of a doomed species.
But there’s one more thing that Neanderthal genes can give us. They mark our genetic code with a haunting reminder. A warning that dates back some 40,000 years.
Climate change can kill any species. Even one as smart as ours.
It’s a warning we’d be wise to heed, before it’s too late.
For Students and Teachers
Review Questions:
- What were some disadvantages of intelligence for hominins?
- What were Neanderthals like?
- Why were Neanderthals relatively vulnerable to extinction by about 50,000 years ago?
- Which theory for the extinction of Neanderthals do you find most persuasive?
Key Publications:
Columbu, Andrea, Veronica Chiarini, Christoph Spötl, Stefano Benazzi, John Hellstrom, Hai Cheng, and Jo De Waele. “Speleothem record attests to stable environmental conditions during Neanderthal–modern human turnover in southern Italy.” Nature Ecology & Evolution 4:9 (2020): 1188-1195.
Devièse, Thibaut, Grégory Abrams, Mateja Hajdinjak, Stéphane Pirson, Isabelle De Groote, Kévin Di Modica, Michel Toussaint et al. “Reevaluating the timing of Neanderthal disappearance in Northwest Europe.” Proceedings of the National Academy of Sciences 118:12 (2021): e2022466118.
Graeber, David, and David Wengrow. The Dawn of Everything: A New History of Humanity. New York: Farrar, Straus and Giroux, 2021.
Greenbaum, Gili, Wayne M. Getz, Noah A. Rosenberg, Marcus W. Feldman, Erella Hovers, and Oren Kolodny. “Disease transmission and introgression can explain the long-lasting contact zone of modern humans and Neanderthals.” Nature communications 10, no. 1 (2019): 1-12.
Platt, Alexander, Daniel N. Harris, and Sarah A. Tishkoff. 2026. “Interbreeding between Neanderthals and Modern Humans Was Strongly Sex Biased.” Science 391:6788 (February 26, 2026): 922–925.
Slimak, Ludovic, Tharsika Vimala, Andaine Seguin-Orlando, Laure Metz, Clément Zanolli, Renaud Joannes-Boyau, Marine Frouin et al. “Long genetic and social isolation in Neanderthals before their extinction.” Cell genomics 4:9 (2024).
Timmermann, Axel. “Quantifying the potential causes of Neanderthal extinction: Abrupt climate change versus competition and interbreeding.” Quaternary Science Reviews 238 (2020): 106331.
Urciuoli, Alessandro, Ignacio Martínez, Rolf Quam, Juan Luis Arsuaga, Brian A. Keeling, Julia Diez-Valero, and Mercedes Conde-Valverde. “Semicircular canals shed light on bottleneck events in the evolution of the Neanderthal clade.” Nature Communications 16:1 (2025): 972.
Vaesen, Krist, Fulco Scherjon, Lia Hemerik, and Alexander Verpoorte. “Inbreeding, Allee effects and stochasticity might be sufficient to account for Neanderthal extinction.” PLoS One 14:11 (2019): e0225117.
Vidal-Cordasco, Marco, Gabriele Terlato, David Ocio, and Ana B. Marín-Arroyo. “Neanderthal coexistence with Homo sapiens in Europe was affected by herbivore carrying capacity.” Science Advances 9:38 (2023): eadi4099.
Video and Audio Credits:
Audio Tools: AIVA, Runway.
Video Tools: Runway, Sora.
Funding provided by Georgetown University’s Earth Commons.
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