These ancient hominids, who disappeared 40,000 years ago, were once thought to be brutish. But recent discoveries have hinted they were more like us than we thought.
When limestone quarry workers in Germany’s Neander Valley discovered fossilized bones in 1856, they thought they’d uncovered the remains of a bear. In fact, they’d stumbled upon something that would change history: evidence of an extinct species of ancient human predecessors who walked the Earth between at least 400,000 and 40,000 years ago.
Researchers soon realized that they had already encountered these human relatives in earlier fossils that had been found, and misidentified, throughout the early 19th century. The discovery galvanized scientists eager to explore new theories of evolution, sparking a worldwide fossil hunt and tantalizing the public with the possibility of a mysterious sister species that once dominated Europe.
Now known as Neanderthals—so named by geologist William King—Homo neanderthalensis are humans’ closest known relatives. Here’s what to know about our human ancestors, including how they lived and why they died out.
What is a Neanderthal?
At first glance, fossilized Neanderthal bones seem human-like. But a closer look reveals the characteristics that differentiate our ancient ancestors from modern Homo sapiens.
Neanderthals looked similar to humans but had more prominent brows, protruding faces, and rib cages that were shorter, deeper, and wider. In addition, their eye sockets were much larger, though it is unclear if their vision differed from ours. Researchers believe that Neanderthal brains were roughly the same size as ours, although they were more elongated. Though debates on the size and structures of Neanderthal brains still rage today, researchers agree that the average male Neanderthal was about 5 foot 4 inches tall, while females stood at about 5 feet.
(You may have more Neanderthal DNA than you think.)
These hominids once lived throughout Eurasia. Researchers believe that due to the species’ adaptation to the region’s cold climates, Neanderthals had compact, massive musculature and would have required up to 4,480 calories a day to survive.
Megafauna like mammoths, elephants, and woolly rhinoceros made hunting an important facet of Neanderthal life. Living and traveling in small groups, they used tools like spears to satiate their meat-heavy diet. They also ate plants—which MIT geobiologist Ainara Sistiaga has said is evidence that Neanderthals “probably ate what was available in different situations, seasons and climates.”
Sometimes, this included eating their own: In 2016, scientists studying Neanderthal remains from a cave in what is now Belgium found “unambiguous evidence of Neanderthal cannibalism in Northern Europe.”
Were Neanderthals intelligent?
Researchers initially assumed Neanderthals were brutish, hairy thugs capable only of crude thought and bloody hunting. But some scientists have changed their tune as evidence has accumulated of some surprisingly human-like characteristics among these human ancestors.
Neanderthals used tools in domestic and hunting contexts, flaking rocks to create weapons, scrapers, and axes. Woodworking was also common—they cut and whittled sticks they used to dig or form spears.
Neanderthals used materials such as flint to make tools that they used as weapons, axes, and more. This specimen is from the Pinilla del Valle site, in the Lozoya Valley, near Madrid, Spain. Several Neanderthal fossils have been found here since excavations begin in the early 2000s.
Despite their assumed ability to withstand the cold, Neanderthals are also thought to have processed animal hides and crafted clothing that could cover up to 80 percent of their bodies. Like humans, they are thought to have covered their feet and other sensitive body parts, but since the clothing has long since disintegrated, researchers can only infer how Neanderthals may have dressed.
Another breakthrough was the discovery that Neanderthals may have been capable of symbolic thought. A few archaeological sites have yielded decorated eagle talons and objects thought to have been used in burial rituals—evidence, some say, of advanced thought and tradition. Then, in 2018, researchers announced they’d discovered evidence of cave paintings from 65,000 years ago—the oldest artworks of their kind. But the abstract nature of this art continues to fuel debates among scientists about how complex their mental capacities truly were.
When and why did Neanderthals go extinct?
Whatever their cognitive abilities, Neanderthals were ultimately doomed. However, their extinction is just as contentious as other facets of their lives, and scientists still debate what caused them to disappear around 40,000 years ago.
Human origins
Over millions of years, Africa incubated a dazzling array of ancient human relatives.
Today, only one branch of the family tree remains: us.
Long lower legs were adapted to walking and running; smaller teeth and larger brains in later H. erectus could indicate they hunted and ate more meat.
New research identifies interbreeding between Denisovans and Neanderthals around 90,000 years ago.
This suggests mixing between early hominin groups may have been common.
Early species were adapted to climbing as well as bipedalism; later species had more specialized diets of tough, fibrous food.
Researchers know that in at least some cases, Neanderthals coexisted and even mated with Homo sapiens, which emerged in Africa about 300,000 years ago. But Homo sapiens eventually won out genetically, and the vast majority of modern humans’ genes come from our African ancestors. Some surmise that competition from humans for food and shelter, or evolution that selected for more successful human traits, contributed to the Neanderthals’ extinction. Others think that because Neanderthals lived in such small groups, they simply became outnumbered by humans.
Another hypothesis involves climate change: Scientists have documented a thousand-year-long cold snap in central Europe that coincided with the Neanderthals’ extinction about 40,000 years ago and that could have depopulated the species. Cooling is thought to have been less severe in areas populated by Homo sapiens, and those who embrace this theory believe that once Neanderthal populations declined, humans moved in and eventually became the dominant species worldwide.
Modern humans and Neanderthal DNA
Despite their species’ demise, fascinating remnants of Neanderthals can be found in the genetic material of some modern humans. Up to 4 percent of the DNA of humans living outside of Africa, the cradle of Homo sapiens, can be traced back to Neanderthals. That overlap shows that Neanderthals did interbreed with humans.
(How do Neanderthal genes affect your health?)
“Ironically,” write prehistory experts Peter C. Kjærgaard, Mark Maslin, and Trine Kellberg Nielsen, “with a current world population of about 8 billion people, this means that there has never been more Neanderthal DNA on Earth.”
Given how long it’s been since Neanderthals roamed Eurasia, it’s impossible to truly reconstruct how they lived and died. But the mystery of these human ancestors—and tantalizing hints that they were much like us—continues to drive research, and controversy, to this day.
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The climate and early human societies were changing quickly during the fall of our closest evolutionary relative—and are big clues to the causes of their demise.
February 28, 2025 NATIONAL GEOGRAPHIC
Neanderthals (Homo neanderthalensis), are the human species that has attracted the most attention as our closest evolutionary relatives. The first fossils related to Neanderthals weren’t recognized as such until 1863, although they were discovered decades earlier. The ongoing intrigue should come as no surprise because, for a long time, Neanderthals were the model for the missing link between our own species, Homo sapiens, and the first apelike pre-human ancestors—but then they disappeared. This is the story of an extinction.
In the past, Neanderthals were thought to be a European species that had disappeared without a trace. It was believed that their physical, intellectual, and technological “inferiority” had driven them to extinction, and that they were then replaced by the Cro-Magnons, early H. sapiens, who were also genuinely European. This progression fit in with 20th-century ideas about evolution, which was seen as an ascending process with H. sapiens at the peak. We were considered the species that had successfully completed the evolutionary process initiated millions of years ago.
(What were Neanderthals really like—and why did they go extinct?)
Today we know that human evolution was much more complex. Advances in research have overturned much of the old pejorative view of Neanderthals and undermined the idea that Europe was key to human evolution. We know now that modern humans and Neanderthals shared a common African ancestor less than 500,000 years ago (which, in evolutionary terms is the blink of an eye). Some have proposed Homo antecessor as that common ancestor of humans and Neanderthals, but this is far from generally accepted.
For much of Homo sapiens’ existence, there were negligible physical differences between them and Neanderthals, and the cultural differences are archaeologically imperceptible. We have found that our distant cousins were as cognitively complex as we are. For a time we even interbred, successfully reproducing and giving rise to hybrid individuals that, in turn, reproduced as well.
(You may have more Neanderthal DNA than you think.)
Migration wave of Homo sapiens out of Africa ~60,000 years ago
The existence of so many similarities and the ability to hybridize have sparked debates for decades. Some researchers argue that H. sapiens and Neanderthals were actually members of a single species, which taxonomy—the classification of living beings—defines as a set of natural populations that are capable of interbreeding and producing fertile offspring. From this point of view, the Neanderthals would be a subspecies that evolved in Europe before being reabsorbed by the populations that arrived from Africa at the end of the Pleistocene (the long period of almost two million years that concluded when the last period of glaciation ended). Other scholars argue that the physical and genetic differences between the classic Neanderthals (those who lived from 200,000 years ago until their extinction) and the H. sapiens of the same period are still sufficient to keep each species in its own taxonomic box.
But there’s something about the history of Neanderthals that continues to fascinate us: They became extinct. Neanderthals disappeared without a trace and were completely replaced by H. sapiens in every location they had inhabited for hundreds of thousands of years.
Similarities and differences
A natural process
Extinction is a natural part of biological evolution. It is estimated that 99.9 percent of all species that have ever existed have disappeared. So we must view the extinction of the Neanderthals as a natural historical process and not as an exception or a rarity.
Many different factors are involved in natural extinction, the most common being competition between species and changes to ecosystems. These may be determining factors in the extinction of taxa or species when their populations face demographic and genetic problems, or they may not affect them at all when populations are in good health.
Figures are difficult to come by when discussing human evolution, but here is an estimate: The Neanderthals became extinct around 40,000 to 37,000 years ago. According to the data currently available, we can safely say that there is no solid evidence that they lasted beyond this threshold. Now that we have a certainty, let’s move on to the nuances.
To find out when an individual or a Neanderthal population lived and, therefore, when it disappeared, we use radiocarbon dating whenever possible. As a result of improvements in these techniques, some Neanderthals previously dated rather recently—such as those from Vindija (Croatia) at 28,000 years, or those from Spy (Belgium) at 30,000 years—are now dated more in accordance with the 40,000 to 37,000-year cutoff. However, some isolated populations were able to survive several millennia longer in certain regions. Ultimately, the very nature of radiometric dating will never give us a firm date for the extinction of Neanderthals but only a range of probability.
From the viewpoint of biology and ecology, a species is considered extinct when its last individual dies. The popular image of the Neanderthals’ demise is a sequence in which a wandering, melancholic individual exhales his last breath in a mountain crevice while remembering his fellows who died before him. For a species to become extinct there obviously has to be a last individual, but nature works in a much more complex way. The affinity between Neanderthals and H. sapiens may have caused the last individuals to mix so that, rather than disappearing, the Neanderthals would have been diluted among the new African migrants.
Before a taxon or species becomes extinct, it may be eradicated or pushed out of one of its natural ranges (e.g., because of changes in climate), thus greatly reducing the territory in which it can be found. Species may even be in a state of functional extinction, in which populations are not viable in the long term becuase of their small size. Recent analysis of DNA from a Neanderthal fossil found in the Mandrin Cave in France’s Rhône Valley reveals that the individual belonged to a hitherto unknown Neanderthal lineage, a tiny community that had remained in genetic isolation from other Neanderthals for some 50,000 years. The ability of these populations to survive isolated for so long shows how extraordinarily resilient they were.
A symbolic culture of their own
Before their final extinction, their populations were probably pushed out of most of their ranges, and they must have become isolated in separate groups with no gene flow between them.
Genomic studies of Neanderthals from the caves of El Sidrón (Asturias, Spain), Vindija (Croatia), Mezmaiskaya (Caucasus), and Altai (Siberia) show that the last populations had very low genetic diversity. That means that they were small and very closed groups with cases of inbreeding. So, although some individuals may have interbred with other human species, by the end, most Neanderthal populations and subpopulations were physically and genetically isolated, and therefore functionally extinct. It is estimated that this process could have taken up to five millennia, between 42,000 and 37,000 years ago.
Retirement in the Mediterranean
Although Neanderthals were once thought to have been exclusively European, their fossils have been found as far east as the Chagyrskaya and Denisova Caves in Altai (Siberia) and in the Bawa Yawan shelter in the Zagros Mountains (Iran).
Certain stone tools allow us to conjecture that Neanderthals may have extended into East Asia and were very common in Central Asia. Therefore, it would be more correct to speak of a Eurasian taxon.
(How a molar, jawbone, and pinkie are rewriting human history.)
However, the last Neanderthal fossils or Mousterian archaeological sites, as the typical Neanderthal culture is called, come from the southern half of Europe. The Iberian Peninsula plays a fundamental role here. It is clear that Neanderthals spent their final centuries in sunny Andalusia, but when exactly they went extinct is a matter of debate. Studies carried out at Boquete de Zafarraya Cave (Málaga, Spain) in 2003 and Gorham’s Cave (Gibraltar) in 2006 yielded very recent dates, ranging between 33,000 and 28,000 years ago. These findings have since been questioned. It cannot be stated with certainty that these sites are less than 40,000 years old.
Other Iberian sites south of the Ebro River—such as Cueva Antón and Sima de las Palomas (Murcia, Spain), Gruta da Oliveira (Portugal), and some levels of Gorham’s Cave—continue to provide relevant data to argue that if the Iberian Peninsula was not the last place where Neanderthals survived, it was the last in western Europe. However, it would not be strange if, in the near future, we found other populations like those in the Iberian Peninsula in Siberia and even farther east.
Tracing Denny’s Neanderthal roots
Climate change and chaos
One of the most important questions in paleoanthropology is why the Neanderthals became extinct. The reality is that we do not know for sure, but there are several hypotheses. A vast amount of time elapsed from the emergence of Neanderthals to their extinction. During the 350,000 or so years of this human species’ existence, the climate changed drastically dozens of times and did so on a global scale. This means that during the more than 13,000 generations of Neanderthals, places like the British Isles went from having sunny summers and mild winters to being buried under tons of ice.
We know that Neanderthals lived through at least 10 major climatic oscillations known as interglacial and glacial periods with stadial (secondary advance of glaciers) and interstadial (recession or standstill of glaciers) periods. Local research indicates that southern Europe, not only the Mediterranean peninsulas but also the northern shore of the Black Sea and the Caucasus, were unaffected by extreme conditions at the coldest times. These areas acted as refuges to which flora and fauna had retreated before the advance of the ice. Once the ice receded, they returned to colonize their former ranges in renewed abundance.
(Neanderthal teeth reveal intimate details of daily life.)
Part of the sixth extinction?
Neanderthals were just pieces on the great ecosystem chessboard, and their range expanded and contracted in step with climate changes.
If Neanderthals had adapted to more or less harsh climate periods dozens of times, did an unpredictable climate make them disappear? Perhaps not by itself. However, it is believed that climate was one of the main factors that pushed this species toward extinction.
The climate was not only chaotic during oscillations; there were also successive tremendously cold pulses caused by the Heinrich and Dansgaard-Oeschger climatic events—a massive iceberg discharge and abrupt warming then a slow cooling of the Earth, respectively. As far as we know, these hominins did not develop technology that would enable them to survive in Arctic biomes; there was never evidence resembling adaptability like that of the Inuit. This feature may be of vital importance in understanding Neanderthal extinction in the context of those times of extreme cold.
While different Neanderthal populations adapted to Mediterranean ecosystems— where it seems they diversified their diet to include an important contribution of vegetables; small animals, such as birds, rabbits, and turtles; and even marine resources—in northern Europe a much more austere way of life prevailed.
There they depended on large herbivores, which were diminishing with the glacial cycles. Often, especially in cold periods, the Neanderthals of the European plains depended heavily on the meat of one or two main prey, such as bison in Mauran or reindeer in the Jonzac rock-shelter (both in France). The animal remains consumed at the sites do not indicate there were famines or shortages in these areas during the latest occupation. However, the more specialized a predator is—and the Neanderthals were exactly that—the easier it is to slide down the slope of extinction when the climatic situation worsens and the number of possible prey decreases.
The middle of the Marine Isotope Stage 3 interglacial (about 45,000 years ago) produced an erratic climate that worsened from time to time. Neanderthal populations divided into small isolated groups, while a new human lineage of more recent African origin was timidly beginning to establish itself in the lower Danube Basin, coming from Africa or Asia.
It was not the first time that Neanderthals and H. sapiens coexisted, as between 100,000 and 55,000 years ago both species had lived alongside one another without apparent conflict in the Near East.
Many researchers argue that competition for resources and territory between the ancient settlers of Europe and the newcomers was the key element in tipping the balance against the Neanderthals.
Although archaeologists do not see too many differences between Neanderthals and H. sapiens in terms of technology, diet, or how they occupied the territory, the first migrant H. sapiens who arrived in Europe brought Upper Paleolithic cultures with them. These included aspects that may have been of great importance in adapting to a world in crisis: needles for sewing elaborate clothing, harpoons for fishing and hunting aquatic animals, spear-throwers for long-distance hunting, and, above all, an impressive panoply of ornaments that indicate the existence of complex networks for long-distance exchange between groups.
Coexistence has been documented through hybrid fossils. These include Oase 1 from the Pestera cu Oase (Romania), a jaw with a mixture of traits from H. sapiens and Neanderthals; and fossils from Bacho Kiro Cave (Bulgaria), which had one grandparent from each species just six to 10 generations before their birth. It has also been proposed that the transitional cultures between the Middle and Upper Paleolithic, such as the Châtelperronian, may have been the product of an exchange of ideas between the two human groups, which coexisted for at least three millennia in most of Europe.
(World’s oldest cave art found—and Neanderthals made it.)
Carved about 13,000 years ago, during the Magdalenian culture, these bone and antler tools are characteristic of the Upper Paleolithic cultures, the work of 
Markings are visable on an imperial eagle claw, worked into an ornament 40,000 years ago.What seems to be ruled out is aggressive confrontation: There is not a shred of evidence that H. sapiens deliberately “exterminated” Neanderthals. This is not a dichotomy between two homogeneous and differentiated human species. Both groups were diverse culturally and (most likely) phenotypically (that is, in their external appearance.)
Caring and sharing in small communities
In some places and in some populations, they must not have differed too much. Nevertheless, contact between the two populations in Europe was likely sporadic. The extinction process of the European Neanderthals happened over an extended period of more than 5,000 years. The structure of Neanderthal populations (small, highly inbred groups), their reproductive strategies, their place in ecosystems, climate chaos, and the reduction in their main prey all created a discouraging panorama. Even large volcanic eruptions and meteorite impacts have been proposed as events that complicated matters for them.
Perhaps if H. sapiens had not been expanding out of Africa, Neanderthal populations would have recolonized all of Eurasia in the following interglacial period for the umpteenth time from their refuges in southern Europe. Maybe they would have lasted many millennia longer. We will never know.
If, after 160 years of studying Neanderthals, we still do not have a definitive answer about their extinction, the path to understanding the disappearance of other human species appears equally long, and no less fascinating.
