Homo neanderthalensis – The Neanderthals

Neanderthals co-existed with modern humans for long periods of time before eventually becoming extinct about 28,000 years ago. The unfortunate stereotype of these people as dim-witted and brutish cavemen still lingers in popular ideology but research has revealed a more nuanced picture.

Age

This species lived between 28,000 and 300,000 years ago

• early Homo neanderthalensis from about 300,000 years ago
• classic Homo neanderthalensis from about 130,000 years ago
• late Homo neanderthalensis from about 45,000 years ago.

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Important fossil discoveries

The first Neanderthal fossil was found in 1829, but it was not recognised as a possible human ancestor until more fossils were discovered during the second half of the 19th century. Since then, thousands of fossils representing the remains of many hundreds of Neanderthal individuals have been recovered from sites across Europe and the Middle East. These include babies, children and adults up to about 40 years of age. As a result, more is known about this human ancestor than about any other.

Key specimens:

• Le Moustier – a 45,000-year-old skull discovered in Le Moustier, France. The distinctive features of Neanderthals are already apparent in this adolescent individual. This shows that these characteristics were genetic and not developed during an individual’s lifetime.
• Shanidar 1 – upper jaw with teeth. The front teeth of Neanderthals often show heavy wear, a characteristic that is even found in young Neanderthals. It is probable that they used their teeth as a kind of vice to help them hold animal skins or other objects as they worked.
• La Ferrassie 1 – a 50,000-year-old skull discovered in 1909 in La Ferrassie, France. This skull of an elderly male has the features associated with ‘classic’ European Neanderthals.
• Amud 1 – a 45,000-year-old skull discovered in1961 by Hisashi Suzuki in Amud, Israel. This individual was more than 180 centimetres tall and had the largest brain of any fossil human (1740 cubic centimetres). Neanderthals probably migrated to the Middle East during times of harsh European winters. These individuals had less robust features than their European counterparts.
• Maba – a partial skull classifed as Homo sp. (species uncertain) and discovered in Maba, China. This partial skull, dated to about 120,000 – 140,000 years old, shows remarkable similarities to European Neanderthals and its discovery in southern China suggests the possibility that Neanderthals travelled further east than once thought. More fossil evidence from Asia is needed to understand the significance of this specimen.
• La Chapelle-aux-Saints – a 50,000-year-old skull discovered in 1908 in La Chapelle-aux-Saints, France. This male individual had lost most of his teeth and his skeleton showed evidence of major injuries and disease including a healed broken hip, and arthritis of the lower neck, back, hip and shoulders. He survived for quite some time with these complaints, which indicates that these people cared for the sick and elderly.
• Neanderthal 1 – a 45,000-year-old skullcap discovered in 1856 in Feldhofer Grotto, Neander Valley, Germany. This is the ‘type specimen’ or official representative of this species.
• Kebara 2 – 60,000-year-old partial skeleton discovered in 1983 in Kebara cave, Israel. This relatively complete skeleton belonged to an adult male. It was deliberately buried but as no grave goods were found it is difficult to infer any ritualistic behaviour.
• Lagar Velho – a 24,000-year-old skeleton of a Homo sapiens boy discovered in 1998 in Abrigo do Lagar Velho, central western Portugal. This specimen has been described by its discoverers (and particularly Eric Trinkhaus) as a Neanderthal-Homo sapiens hybrid. This interpretation was based on knee and leg proportions but as the head, pelvis and forearms are decidedly human it is more likely that the robustness is a climatic adaptation (see Tattersal and Schwartz). Comparisons to other humans of this period are difficult due to lack of knowledge on variations within child populations.

What the Neanderthal name means

Homo, is a Latin word meaning ‘human’ or ‘man’. The word neanderthalensis is based on the location where the first major specimen was discovered in 1856 – the Neander Valley in Germany. The German word for valley is ‘Tal’ although in the 1800s it was spelt ‘Thal’. Homo neanderthalensis therefore means ‘Human from the Neander Valley’.

Some people refer to this species as the Neandertals (with no 'h') to reflect the modern German spelling rather than the original spelling, Neanderthal, used to define the species.

Distribution

Remains of this species have been found scattered across Europe and the Middle East. The eastern-most occurrence of a Neanderthal may be represented by a fossil skull from China known as ‘Maba’.

A study published in 2009 confirms the presence of three separate sub-groups of Neanderthals, between which slight differences could be observed, and suggests the existence of a fourth group in western Asia. The study analysed the genetic variability, and modelled different scenarios, based on the genetic structure of the maternally transmitted mitochondrial DNA (mtDNA). The study was possible thanks to the publication, since 1997, of 15 mtDNA sequences from 12 Neanderthals. According to the study, the size of the Neanderthal population was not constant over time and a certain amount of migration occurred among the sub-groups.

Relationships with other species

While we are closely related to the Neanderthals, they are not our direct ancestors. Evidence from the fossil record and genetic data shows they are a distinct species that developed as a side branch in our family tree. Some European Homo heidelbergensis fossils were showing early Neanderthal-like features by about 300,000 years ago and it is likely that Neanderthals evolved in Europe from this species.

The name Homo sapiens neanderthalensis was once common when Neanderthals were considered to be members of our own species, Homo sapiens. This view and name are no-longer favoured.

Interbreeding with modern humans?

Groundbreaking analysis of the Neanderthal genome (nuclear DNA and genes) published in 2010 shows that modern humans and Neanderthals did interbreed, although on a very limited scale. Researchers compared the genomes of five modern humans with the Neanderthal, discovering that Europeans and Asians share about 1-4% of their DNA with Neanderthals and Africans none. This suggests that modern humans bred with Neanderthals after moderns left Africa but before they spread to Asia and Europe. The most likely location is the Levant, where both species co-existed for thousands of years at various times between 50-90,000 years ago. Interestingly, the data doesn't support wide-scale interbreeding between the species in Europe, where it would have been most likely given their close proximity. Researchers are now questioning why interbreeding occurred on such a low scale, given that it was biologically possible. The answer may lie in cultural differences.

Sharing Europe with the Denisovians?

Did the Neanderthals also live alongside another human species in Europe? An interesting case making headlines in 2010 was the discovery of a finger bone and tooth from Denisova cave in Russia. The bones were found in 2008 and date to about 30,000-50,000 years old. Mitochondrial DNA (mtDNA) was extracted from the remains, and then sequenced. The result was that the mtDNA did not match either modern human or Neanderthal mtDNA.

Little else could be gleaned from these studies so scientists started work on extracting nuclear DNA. This produced far more information. The 'Denisovians', as they have been nicknamed, were more closely related to Neanderthals than modern humans. This suggests the Neanderthals and 'Denisovans' shared a common ancestor after modern humans and Neanderthals split. Perhaps this ancestor left Africa half a million years ago with the Neanderthals spreading west to the Near East and Europe while the Denisovans headed east. However, this does not necessarily mean they are a 'new' species as they may be already known from fossils that have no DNA record to compare, such as Homo heidelbergensis or H. antecessor. (See Nature, December 2010)s

Neanderthals are recognisably human but have distinctive facial features and a stocky build that were evolutionary adaptations to cold, dry environments.

Body size and shape

• Neanderthals were generally shorter and had more robust skeletons and muscular bodies than modern humans
• males averaged about 168 centimetres in height while females were slightly shorter at 156 centimetres.

Brain

• brain size was larger than the average modern human brain and averaged 1500 cubic centimetres. This is expected, as Neanderthals were generally heavier and more muscular than modern humans. People that live in cold climates also tend to have larger brains than those living in warm climates.

Skull

• distinctive skull shape that was long and low, with a rounded brain case
• back of the skull had a bulge called the occipital bun and a depression (the suprainiac fossa) for the attachment of strong neck muscles
• thick but rounded brow ridge lay under a relatively flat and receding forehead
• mid-face region showed a characteristic forward projection (this resulted in a face that looked like it had been ‘pulled’ forward by the nose)
• orbits (eye sockets) were large and rounded
• nose was broad and very large

Jaws and teeth

• jaws were larger and more robust than those of modern humans and had a gap called the retromolar space, behind the third molars (wisdom teeth) at the back of the jaw.
• jaw lacked the projecting bony chin that is found in Homo sapiens.
• teeth were larger than those of modern humans.

Limbs and pelvis

• limb bones were thick and had large joints which indicates they had strongly muscled arms and legs
• shin bones and forearms tended to be shorter than those of modern humans. These proportions are typical for people living in cold climates.
• pelvis was wider from side to side than in modern humans and this may have slightly affected their posture

DNA and biomolecular studies

• Neanderthals are our only ancestors to have had studies performed on their DNA and other biomolecules. Although numerous studies have been undertaken since the first was published in 1997 (on mitochondrial DNA), the most significant is the publication in 2009 of the rough draft of the Neanderthal genome.
• Other key findings on from a variety of studies include the discovery of: a gene for red hair and fair skin (2007): the FOXP2 gene, related to language ability, that was the same as modern humans; type O blood in two males from Spain (2008)

Neanderthals Culture

Evidence shows that Neanderthals had a complex culture although they did not behave in the same ways as the early modern humans who lived at the same time. Scholars debate the degree of symbolic behaviour shown by Neanderthals as finds of art and adornment are rare, particularly when compared to their modern human contemporaries who were creating significant amounts of cave paintings, portable art and jewellery. Some researchers believe they lacked the cognitive skills to create art and symbols and, in fact, copied from or traded with modern humans rather than create their own artefacts. However, others suggest the scarcity may have been due to social and demographic factors.

Tools

The Neanderthals had a reasonably advanced tool kit classified as Mode 3 technology that was also used by early members of our own species, Homo sapiens. This was also known as the Mousterian, named after the site of Le Moustier. At the end of their long history in Europe, they began manufacturing a more refined toolkit (known as the Chatelperronian), similar to the blade tools of Homo sapiens. This occurred at about the same time as modern humans entered Europe. Many archaeologists think that the Neanderthals were attempting to copy the types of tools that they observed modern humans making. Alternatively, they may have obtained these tools by trading with the modern humans.

Fire, shelter and clothing

The Neanderthals built hearths and were able to control fire for warmth, cooking and protection. They were known to wear animal hides, especially in cooler areas. However, there is no physical evidence that Neanderthal clothing was sewed together, and it may have simply been wrapped around the body and tied.

Caves were often used as shelters but open air shelters were also constructed.

Art and decoration

Neanderthals left behind no known symbolic art and only limited evidence for body decoration. One of few decorative items found at a Neanderthal site is a pendant from Arcy-sur-Cure in France, found amongst bone tools and other artefacts that were attributed to a culture known as Chatelperronian (which most researchers consider Neanderthal). However, redating of the site's layers in 2010 suggest contamination occurred between layers and that the artefact may have been made by modern humans, as they also occupied this site in later times. There is only one other undisputed Chatelperronian site that has yielded personal ornaments, and even these may have been obtained by trade with modern humans (Homo sapiens), or been made in imitation of artefacts made by modern humans.

In 2010 researchers uncovered artefacts at two sites in Spain - Anton rock shelter and Aviones cave - that provide indirect evidence of symbolic art. The former held naturally-perforated scallop shells painted with orange pigments and the latter a cockleshell that may have been used as a paint container as it had residue of red and black pigments. The Avione finds date to between 45-50,000 years ago, which is before modern humans arrived in Europe so could not have been copied from them.

Burials

The dead were often buried, although there is no conclusive evidence for any ritualistic behaviour. However, at some sites, objects have been uncovered that may represent grave goods.

Environment and diet

This species occupied a range of environments across Europe and the Middle East and lived through a period of changing climatic conditions. Ice Ages in Europe were interspersed with warmer periods but by 110,000 years ago average temperatures were on the decline and full glacial conditions had appeared by 40,000 years ago.

There is evidence that the Neanderthals hunted big game and chemical analysis of their fossils shows that they ate significant amounts of meat supplemented with vegetation. Despite this mixed diet, nearly half of the Neanderthal skeletons studied show the effects of a diet deficient in nutrients.

Researchers have long debated whether Neanderthals also included human meat in their diets. It is not always easy to determine if cut marks on human bones are due to cannabilism, some other practice or even animal teeth, but in recent years new evidence has emerged that suggests some Neanderthals may indeed have been cannibals on occasions.

• At the site of Krapina Cave in Croatia, over 800 Neanderthal bones show evidence of cut marks and hammerstone fragments. The marrow-rich bones are missing and the marrow-poor bones are all in tact. Some argue that the evidence is inconclusive as the fragmentation of bones may have been caused by cave-ins and the bone cuts are different to the marks seen on reindeer bones. They claim the cut marks could be from secondary burial practises.
• Bones from Abri Moula in France show cut marks typical of butchery rather than simple ritual defleshing. The marks were also like those on the bones of roe deer, assumed to be food, found in the same shelter.
• The cave of El Sidron in Spain yielded hundreds of Neanderthal bones with cut marks, deliberate breaks for marrow extraction, and other signs that the bodies had been butchered for flesh in the same way as animals.

Neanderthals persisted for hundreds of thousands of years in extremely harsh conditions. They shared Europe for 10,000 years with Homo sapiens. Today they no longer exist. Beyond these facts the fate of Neanderthals has generated much debate.

Two main theories

Theory 1: They interbred with Homo sapiens sapiens on a relatively large scale. Followers of this theory believe that although Neanderthals as organisms no longer exist their genes were present in early modern Europeans and may still exist today. Interbreeding diluted Neanderthal DNA because there were significantly more Homo sapiens sapiens. Neanderthals were a sub-species of Homo sapiens rather than a separate species and hence their scientific name is Homo sapiens neanderthalensis.

Proponents of this theory cite the following as evidence:

• there are features of Neanderthals in some Cro-Magnon (Homo sapiens) populations. For instance the discoverers of the 24,000-year-old skeleton of a modern human boy from Lagar Velho in Portugal, argue that although the pelvis and facial morphology are sapien-like, the robusticity and limb proportions are more Neanderthal-like. As the age of the skeleton is later than the time of the last known Neanderthal, these features must represent significant interbreeding and transmission of DNA between modern humans and Neanderthals. Cro-magnon remains from Vogelherd in Germany and Mladec in the Czech Republic also exhibit a Neanderthal-like projection of the occipital bun at the back of the skull, more so than in later Homo sapiens.
• there are modern features in later Neanderthal populations. The Vindija Neanderthals look more modern than do other Neanderthals, which suggests that they may have interbred with incoming Homo sapiens.
• there are features of Neanderthals in modern Europeans. Some Europeans living today have a similar shaped mandibular foramen (nerve canal in lower jaw) to the Neanderthals and the distinct retromolar gap (typical of Neanderthals) appears in isolated modern European populations.

Theory 2: They were essentially replaced by Homo sapiens. In this case, Neanderthals are a separate species from Homo sapiens. This model does allow for peripheral interbreeding but no significant genetic input from Neanderthals to modern Europeans.

Proponents of this theory cite the following as evidence:

• studies of Neanderthal mitochondrial DNA (first extracted in 1997) show that it lies outside the range of modern human mtDNA. Neanderthal mtDNA is four times older than that of Homo sapiens, hence scientists postulate a Neanderthal split from the line leading to modern humans about 500-600,000 years ago. The studies also reveal that Neanderthal mtDNA is no closer to modern European mtDNA than moderns from any other part of the world.
• analysis of the draft Neanderthal genome (the nuclear DNA and genes), released in 2010, shows that modern human and Neanderthal lineages began to diverge about 600,000 years ago. It also indicates that there was small-scale interbreeding as non-Africans derive about 1-4% of their DNA from Neanderthals. These results challenge the simplest version of 'Out of Africa' (which claims no interbreeding in its model for modern human origins) but do support the view that the vast majority of genes of non-Africans came with the spread of modern humans that originated in Africa.
• studies of the facial growth patterns of young Neanderthals show they developed in distinct ways to Homo sapiens. The differences are therefore deeply genetic, contradicting the evidence of the Lagar Velho boy. The distinctive features include brow ridges, chins, forehead and facial protrusion.

Various reasons have been proposed for the ‘replacement’ of Neanderthals by modern humans. Today, most theories accept that Neanderthals displayed advanced behaviours and adaptive strategies and were not sluggish brutes that stood no chance against the vastly superior Homo sapiens. However,the incoming Homo sapiens were doing something that was different enough, and just that little bit more superior, to give them an edge under the circumstances. Exactly what was 'a little bit more superior' is debated. Of particular interest are a number of new studies that focus on the role of climate change and the subtle differences that behaviour and biology play in these conditions.

Perhaps their extinction was a combination of two or more of the following factors:

Biological

• Neanderthal reproductive success and survival rates appear poor compared to Homo sapiens. Most Neanderthal remains are of individuals rarely over 30 years old and over half are children. Slightly better rates of reproductive success and childhood survival over 10,000 years could be all it took for Homo sapiens to replace Neanderthals.
• Neanderthal metabolic rates appeared to be much higher than modern humans so would have required more food to survive. In situations of plenty this would make little difference, but in severe winters or unstable climatic conditions (see below), the dwindling resources would put pressure on populations that needed large amounts of energy from food.
• Claims that Neanderthals could not run as well as modern humans over long distances is supported by evidence from Neanderthal ankles. Their heal bones are longer than modern humans', resulting in a longer Achilles tendon. Shorter Achilles, as in modern humans, store more energy so are more efficient for running. Neanderthals generally didn't need to be good long-distance runners as they hunted in cooler regions using ambush tactics, but when conditions changed this could prove a huge disadvantage. Evidence suggests this happened 50,000 years ago as much of northern Europe changed from forest to tundra due to advancing ice sheets. Neanderthals were forced into isolated forest refuges in southern areas while modern humans adapted to hunting on the increasingly widespread tundra.

Social and behavioural

• Neanderthal culture lacks the depth of symbolic and progressive thought displayed by modern humans and this may have made competing difficult. Neanderthal culture remained relatively static whereas the contemporary Homo sapiens were steadily evolving a complex culture. By the time Homo sapiens arrived in Europe 40,000 years ago they had a highly developed cultural system. This is despite the fact that 100,000 years ago there is relatively no cultural difference between either species in the archaeological record.
• Neanderthals may have had limited speech and language capabilities compared to Homo sapiens and the extent of the differences may have played a role in their extinction. For instance, studies of the base of the skull suggest limited Neanderthal repertoire and the position of the tongue in the mouth and larynx is also different from Homo sapiens. (This is a highly contentious theory with scientists on both sides strongly arguing for or against).
• Neanderthals may have lacked the adaptive nature of modern humans who had complex social networks across wide areas. Smaller populations of Neanderthals that tended to stay in limited areas may have made them vulnerable to local extinctions.
• The survival techniques of Neanderthals were not as developed as Homo sapiens. For instance, studies on stress and build-up of tissue in Neanderthal bones indicate they may have lacked systematic and directional planning in procuring food. This Neanderthal predominance of ‘brawn over brain’ may also be reflected in the number of skeletal injuries seen in both sexes, probably from close range hunting. Other studies show that 40% of Neanderthal remains have hypoplasia, a condition caused by lack of nutrients in early childhood. This is supported by tests on Neanderthal bone collagen which indicate that meat was very significant in Neanderthal diets to the point that they may be lacking the nutrients from other sources used by Homo sapiens, especially fresh water products and vegetable matter.
• Neanderthals may not have used their brains they way modern humans do as their brains were shaped differently - modern human brains have expanded parietal and cerebellar regions. These regions develop in the first year of life (Neanderthal infants appear to miss this stage of development) and are linked to key functions like the ability to integrate sensory information and form abstract representations of surroundings.
• Possible violent interactions with modern humans.

Environment or climate

• New data on the glacial period that occurred from about 65,000 to 25,000 years ago (known as OIS-3) shows that it was a period of rapid, severe and abrupt climate changes with profound environmental impacts. Although Neanderthals were physically adapted to the cold, the severe changes in conditions (within individuals' lifetimes in many cases) allowed no time for populations to recover. Even small advantages in biology, behaviour or lifestyle, such as those mentioned above, would mean the difference between life and death. The archaeological record indicates that modern humans had a wider range of adaptations which would have helped in survival.
• There is another angle to the climate change theory. Evidence based on extensive surveys of sites in Europe suggests that Neanderthal replacement was not due to direct competition with modern humans. Instead, evidence suggests that the severe conditions made the continent inhospitable for all humans living in Europe - and all populations died out about 30-28,000 years ago. However, there were other modern human populations living in Africa that were able to recolonise Europe at a later date. As there were no Neanderthal populations elsewhere, they became extinct.