Neanderthal

The Neanderthals (English pronunciation /niˈændərˌθɔːlz/, /niˈændərˌtɔːlz/, /niˈændərˌtɑːlz/ or /neɪˈɑːndərˌtɑːlz/) are an extinct species or subspecies of the genus Homo which is closely related to modern humans. They are known from fossils, dating from the Pleistocene period, which have been found in Europe and parts of western and central Asia. The species is named after Neandertal ("Neander's Valley"), the location in Germany where it was first discovered. The species name is also sometimes spelled Neandertal, because that is the modern German spelling of the valley's name.

Neanderthals are classified either as a subspecies of Homo sapiens (Homo sapiens neanderthalensis) or as a separate species of the same genus (Homo neanderthalensis). The first humans with proto-Neanderthal traits are believed to have existed in Europe as early as 600,000–350,000 years ago.

When the Neanderthals went extinct is disputed. Fossils found in the Vindija Cave in Croatia have been dated to between 33,000 and 32,000 years old, and Neanderthal artefacts from Gorham's Cave in Gibraltar are believed to be less than 30,000 years ago, but a recent study has re-dated fossils at two Spanish sites as 45,000 years old, 10,000 years older than previously thought, and may cast doubt on recent dates at other sites. Cro-Magnon (early-modern-human) skeletal remains showing certain "Neanderthal traits" have been found in Lagar Velho (Portugal) and dated to 24,500 years ago, suggesting that there may have been an extensive admixture of the Cro-Magnon and Neanderthal populations in that region.

Several cultural assemblages have been linked to the Neanderthals in Europe. The earliest, the Mousterian stone tool culture, dates to about 300,000 years ago. Late Mousterian artifacts were found in Gorham's Cave on the south-facing coast of Gibraltar. Other tool cultures associated with the Neanderthals include the Châtelperronian, the Aurignacian, and the Gravettian; their tool assemblages appear to have developed gradually within their populations, rather than being introduced by new population groups arriving in the region.

Neanderthal cranial capacity is thought to have been as large as that of modern humans, perhaps larger, indicating that their brain size may have been comparable, or larger, as well. In 2008, a group of scientists created a study using three-dimensional computer-assisted reconstructions of Neanderthal infants based on fossils found in Russia and Syria. The study showed Neanderthal and modern human brains were the same size at birth, but by adulthood, the Neanderthal brain was larger than the modern human brain. They were much stronger than modern humans, having particularly strong arms and hands. Males stood 164–168 cm (65–66 in) and females about 152–156 cm (60–61 in) tall.

Genetic evidence published in 2010 suggests that Neanderthals contributed to the DNA of anatomically modern humans, probably through interbreeding between 80,000 and 50,000 years ago with the population of anatomically modern humans who had recently migrated from Africa. According to the study, by the time that population began dispersing across Eurasia, Neanderthals genes constituted as much as 1–4% of its genome.

Etymology

The species is named after the site of its first discovery, about 12 km (7.5 mi) east of Düsseldorf, Germany, in the Feldhofer Cave in the river Düssel's Neander valley named for Joachim Neander, a 17th-century German pastor and hymnist. Neander's own name was a Greek translation of the German Neumann (lit. "New man"). Thal is the older spelling of Tal (both with the same pronunciation), the German word for 'valley' (cognate with English dale).

Neanderthal 1 was known as the "Neanderthal skull" or "Neanderthal cranium" in anthropological literature, and the individual reconstructed on the basis of the skull was occasionally called "the Neanderthal man". The binomial name Homo neanderthalensis – extending the name "Neanderthal man" from the individual type specimen to the entire species – was first proposed by the Anglo-Irish geologist William King in 1864 and this had priority over the proposal put forward in 1866 by Ernst Haeckel, Homo stupidus. The practice of referring to "the Neanderthals" and "a Neanderthal" emerged in the popular literature of the 1920s.

The German pronunciation of Neanderthaler and Neandertaler is [neˈandɐˌtʰaːlɐ] in the International Phonetic Alphabet. In British English, "Neanderthal" is spoken with the hard German /t/ but different vowels (IPA: /niːˈændərtɑːl/). In layman's American English, "Neanderthal" is pronounced with a /θ/ (the voiceless th as in thin) and /ɔ/ instead of the longer British /aː/ (IPA: /niːˈændərθɔːl/), although scientists typically use the hard German /t/.

Discovery

Neanderthal skulls were first discovered in Engis Caves ( fr), in what is now Belgium (1829) by Philippe-Charles Schmerling and in Forbes' Quarry, Gibraltar, dubbed Gibraltar 1 (1848), both prior to the type specimen discovery in a limestone quarry of the Neander Valley in Erkrath near Düsseldorf in August 1856, three years before Charles Darwin's On the Origin of Species was published.

The type specimen, dubbed Neanderthal 1, consisted of a skull cap, two femora, three bones from the right arm, two from the left arm, part of the left ilium, fragments of a scapula, and ribs. The workers who recovered this material originally thought it to be the remains of a bear. They gave the material to amateur naturalist Johann Carl Fuhlrott, who turned the fossils over to anatomist Hermann Schaaffhausen. The discovery was jointly announced in 1857.

To date, the bones of over 400 Neanderthals have been found.

Classification

For some time, scientists have debated whether Neanderthals should be classified as Homo neanderthalensis or Homo sapiens neanderthalensis, the latter placing Neanderthals as a subspecies of H. sapiens. Some morphological studies support the view that H. neanderthalensis is a separate species and not a subspecies. Others, for example University of Cambridge Professor Paul Mellars, say "no evidence has been found of cultural interaction" and evidence from mitochondrial DNA studies have been interpreted as evidence Neanderthals were not a subspecies of H. sapiens. Since species can be defined by reproductive isolation, strong genomic evidence of interbreeding between the two races has led some scientists to incline toward classifying the Neanderthal as a subspecies of H. sapiens, but there are documented examples of fertile inter-specific hybridization and introgression, so this is not definitive.

Origin

Comparison of the DNA of Neanderthals and homo sapiens suggests that they diverged from a common ancestor between 350,000 and 400,000 years ago. This ancestor is not certain, but was probably Homo heidelbergensis (sometimes called homo rhodesiensis). Heidelbergensis originated between 800,000 and 1,300,000 years ago, and continued until about 200,000. It ranged over east and south Africa, Europe and west Asia. Between 350,000 and 400,000 years ago the African branch is thought to have started evolving towards modern humans and the European branch towards Neanderthals. Scientists do not agree when Neanderthals can first be recognised in the fossil record, with dates ranging 200,000 and 300,000 years BP.

Timeline

• 1829: Neanderthal skulls were discovered in Engis, in present-day Belgium.
• 1848: Neanderthal skull Gibraltar 1 found in Forbes' Quarry, Gibraltar. Called "an ancient human" at the time.
• 1856: Johann Karl Fuhlrott first recognized the fossil called "Neanderthal man", discovered in Neanderthal, a valley near Mettmann in what is now North Rhine-Westphalia, Germany.
• 1880: The mandible of a Neanderthal child was found in a secure context and associated with cultural debris, including hearths, Mousterian tools, and bones of extinct animals.
• 1886: Two nearly perfect skeletons of a man and woman were found at Spy, Belgium at the depth of 16 ft with numerous Mousterian-type implements.
• 1899: Hundreds of Neanderthal bones were described in stratigraphic position in association with cultural remains and extinct animal bones.
• 1899: Sand excavation workers found bone fragments on a hill in Krapina, Croatia called Hušnjakovo brdo. Local Franciscan friar Dominik Antolković requested Dragutin Gorjanović-Kramberger to study the remains of bones and teeth that were found there.
• 1905: During the excavation in Krapina more than 5 000 items were found, of which 874 residue of human origin, including bones of prehistoric man and animals, artifacts.
• 1908: A nearly complete Neanderthal skeleton was discovered in association with Mousterian tools and bones of extinct animals.
• 1925: Francis Turville-Petre finds the ' Galilee Man' or 'Galilee Skull' in the Zuttiyeh Cave in Wadi Amud in Palestine (now Israel).
• 1926 Skull fragments of Gibraltar 2, a four-year-old Neanderthal girl, discovered by Dorothy Garrod.
• 1953–1957: Ralph Solecki uncovered nine Neanderthal skeletons in Shanidar Cave in the Kurdistan region of northern Iraq.
• 1975: Erik Trinkaus' study of Neanderthal feet confirmed they walked like modern humans.
• 1987: Thermoluminescence results from Israeli fossils date Neanderthals at Kebara to 60,000 BP and humans at Qafzeh to 90,000 BP. These dates were confirmed by electron spin resonance (ESR) dates for Qafzeh (90,000 BP) and Es Skhul (80,000 BP).
• 1991: ESR dates showed the Tabun Neanderthal was contemporaneous with modern humans from Skhul and Qafzeh.
• 1993: A 127.000 years old DNA is found on the child of Sclayn, found in Scladina ( fr), Belgium.
• 1997: Matthias Krings et al. are the first to amplify Neanderthal mitochondrial DNA ( mtDNA) using a specimen from Feldhofer grotto in the Neander valley.
• 1998: A team led by pre-history archeologist João Zilhão discovered an early Upper Paleolithic human burial in Portugal, at Abrigo do Lagar Velho, which provided evidence of early modern humans from the west of the Iberian Peninsula. The remains, a largely complete skeleton of an approximately 4-year-old child, buried with pierced shell and red ochre, is dated to ca. 24,500 years BP. The cranium, mandible, dentition, and postcrania present a mosaic of European early modern human and Neanderthal features.
• 2000: Igor Ovchinnikov, Kirsten Liden, William Goodman et al. retrieved DNA from a Late Neanderthal (29,000 BP) infant from Mezmaiskaya Cave in the Caucasus.
• 2005: The Max Planck Institute for Evolutionary Anthropology launched a project to reconstruct the Neanderthal genome.
• 2006: The Max Planck Institute for Evolutionary Anthropology announced it planned to work with Connecticut-based 454 Life Sciences to reconstruct the Neanderthal genome.
• 2009: The Max Planck Institute for Evolutionary Anthropology announced the "first draft" of a complete Neanderthal genome is completed.
• 2010: Comparison of Neanderthal genome with modern humans from Africa and Eurasia shows that 1–4% of modern non-African human genome might come from the Neanderthals.
• 2010: Discovery of Neanderthal tools far away from the influence of H. sapiens indicate that the species might have been able to create and evolve tools on its own, and therefore be more intelligent than previously thought. Furthermore, it was proposed that the Neanderthals might be more closely related to Homo sapiens than previously thought and that may in fact be a sub species of it. Evidence has more recently emerged that these artifacts are probably of H. sapiens sapiens origin.
• 2012: Charcoal found next to six paintings of seals in Nerja caves, Malaga, Spain, has been dated to between 42,300 and 43,500 years old. The paintings themselves will be dated in 2013, and if their pigment matches the date of the charcoal, they would be the oldest known cave paintings. José Luis Sanchidrián at the University of Cordoba, Spain believes the paintings are more likely to have been painted by Neanderthals than early modern humans.

Habitat and range

Early Neanderthals lived in the Last glacial period for a span of about 100,000 years. Because of the damaging effects the glacial period had on the Neanderthal sites, not much is known about the early species. Countries where their remains are known include most of Europe south of the line of glaciation, roughly along the 50th parallel north, including most of Western Europe, including the south coast of Great Britain, Central Europe and the Balkans, some sites in Ukraine and in western Russia and east of Europe in Siberia to the Altai Mountains and south through the Levant to Indus River. It is estimated that the total Neanderthal population across this habitat range numbered at around 70,000 at its peak.

Neanderthal fossils have not been found to date in Africa, but there have been finds rather close to Africa, both on Gibraltar and in the Levant. At some Levantine sites, Neanderthal remains, in fact, date after the same sites were vacated by modern humans. Mammal fossils of the same time period show cold-adapted animals were present alongside these Neanderthals in this region of the Eastern Mediterranean. This implies Neanderthals were better adapted biologically to cold weather than modern humans and at times displaced them in parts of the Middle East when the climate got cold enough.

Homo sapiens sapiens appears to have been the only human type in the Nile River Valley during these periods, and Neanderthals are not known to have ever lived south-west of modern Israel. When further climate change caused warmer temperatures, the Neanderthal range likewise retreated to the north along with the cold-adapted species of mammals. Apparently these weather-induced population shifts took place before modern people secured competitive advantages over the Neanderthal, as these shifts in range took place well over ten thousand years before modern people totally replaced the Neanderthal, despite the recent evidence of some successful interbreeding.

There were separate developments in the human line, in other regions such as Southern Africa, that somewhat resembled the European and Western/Central Asian Neanderthals, but these people were not actually Neanderthals. One such example is Rhodesian Man ( Homo rhodesiensis) who existed long before any classic European Neanderthals, but had a more modern set of teeth, and arguably some H. rhodesiensis populations were on the road to modern H. sapiens sapiens. At any rate, the populations in Europe and West/Central Asia underwent more and more "Neanderthalization" as time went on. There is some argument that H. rhodesiensis in general was ancestral to both modern humans and Neanderthals, and that at some point the two populations went their separate ways, but this supposes that H. rhodesiensis goes back to around 600,000 years ago.

To date, no intimate connection has been found between these similar archaic people and the Western/Central Eurasian Neanderthals, at least during the same time as classic Eurasian Neanderthals, and H. rhodesiensis seems to have lived about 600,000 years ago, long before the time of classic Neanderthals. This said, some researchers think that H. rhodesiensis may have lived much later than this period, depending on the method used to date the fossils, leaving this issue open to debate. Some H. rhodesiensis features, like the huge brow ridge, may have been caused by convergent evolution. There is no evidence to date that Neanderthals knew how to construct boats or rafts, and the paucity of human fossils in North Africa west of the Nile Valley should be noted.

It appears incorrect, based on present research and known fossil finds, to refer to any fossils outside Europe or Western and Central Asia as true Neanderthals. They had a known range that possibly extended as far east as the Altai Mountains, but not farther to the east or south, and apparently not into Africa. At any rate, in North-East Africa the land immediately south of the Neanderthal range was possessed by modern humans Homo sapiens idaltu or Homo Sapiens, since at least 160,000 years before the present. 160,000 year old hominid fossils at Jebel Irhoud in Morocco were previously thought to be Neanderthal, but it is now clear that they are early modern humans.

Classic Neanderthal fossils have been found over a large area, from northern Germany to Israel and Mediterranean countries like Spain and Italy in the south and from England and Portugal in the west to Uzbekistan in the east. This area probably was not occupied all at the same time. The northern border of their range, in particular, would have contracted frequently with the onset of cold periods. On the other hand, the northern border of their range as represented by fossils may not be the real northern border of the area they occupied, since Middle Palaeolithic-looking artifacts have been found even further north, up to 60° N, on the Russian plain. Recent evidence has extended the Neanderthal range by about 1,250 miles (2,010 km) east into southern Siberia's Altai Mountains.

Anatomy

Neanderthal anatomy was more robust than anatomically modern humans and they had less neotenized skulls.

Behaviour

Neanderthals made advanced tools, had a language (the nature of which is debated) and lived in complex social groups. The Molodova archaeological site in eastern Ukraine suggests some Neanderthals built dwellings using animal bones. A building was made of mammoth skulls, jaws, tusks and leg bones, and had 25 hearths inside.

While largely carnivorous, and apex predators; new studies indicate Neanderthals had cooked vegetables in their diet. In 2010, a U.S. researcher reported finding cooked vegetable matter in the teeth of a Neanderthal skull, contradicting the earlier belief they were exclusively (or almost exclusively) carnivorous and apex predators.

Genome

Early investigations concentrated on mitochondrial DNA (mtDNA), which, owing to strictly matrilineal inheritance and subsequent vulnerability to genetic drift, is of limited value in evaluating the possibility of interbreeding of Neanderthals with Cro-Magnon people.

In 1997, geneticists were able to extract a short sequence of DNA from Neanderthal bones from 30,000 years ago. The extraction of mtDNA from a second specimen was reported in 2000, and showed no sign of modern human descent from Neanderthals.

In July 2006, the Max Planck Institute for Evolutionary Anthropology and 454 Life Sciences announced that they would sequence the Neanderthal genome over the next two years. This genome is expected to be roughly the size of the human genome, three-billion base pairs, and share most of its genes. It was hoped the comparison would expand understanding of Neanderthals, as well as the evolution of humans and human brains.

Svante Pääbo has tested more than 70 Neanderthal specimens. Preliminary DNA sequencing from a 38,000-year-old bone fragment of a femur found at Vindija Cave, Croatia, in 1980 showed Neanderthals and modern humans share about 99.5% of their DNA. From mtDNA analysis estimates, the two species shared a common ancestor about 500,000 years ago. An article appearing in the journal Nature has calculated the species diverged about 516,000 years ago, whereas fossil records show a time of about 400,000 years ago. A 2007 study pushes the point of divergence back to around 800,000 years ago.

Edward Rubin of the Lawrence Berkeley National Laboratory states recent genome testing of Neanderthals suggests human and Neanderthal DNA are some 99.5% to nearly 99.9% identical.

On 16 November 2006, Lawrence Berkeley National Laboratory issued a press release suggesting Neanderthals and ancient humans probably did not interbreed. Edward M. Rubin, director of the U.S. Department of Energy's Lawrence Berkeley National Laboratory and the Joint Genome Institute (JGI), sequenced a fraction (0.00002) of genomic nuclear DNA (nDNA) from a 38,000-year-old Vindia Neanderthal femur. They calculated the common ancestor to be about 353,000 years ago, and a complete separation of the ancestors of the species about 188,000 years ago.

Their results show the genomes of modern humans and Neanderthals are at least 99.5% identical, but despite this genetic similarity, and despite the two species having coexisted in the same geographic region for thousands of years, Rubin and his team did not find any evidence of any significant crossbreeding between the two. Rubin said, "While unable to definitively conclude that interbreeding between the two species of humans did not occur, analysis of the nuclear DNA from the Neanderthal suggests the low likelihood of it having occurred at any appreciable level."

In 2008 Richard E. Green et al. from Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany published the full sequence of Neanderthal mitochondrial DNA (mtDNA) and suggested "Neanderthals had a long-term effective population size smaller than that of modern humans." Writing in Nature about Green et al.'s findings, James Morgan asserted the mtDNA sequence contained clues that Neanderthals lived in "small and isolated populations, and probably did not interbreed with their human neighbours."

In the same publication, it was disclosed by Svante Pääbo that in the previous work at the Max Planck Institute that "Contamination was indeed an issue," and they eventually realized that 11% of their sample was modern human DNA. Since then, more of the preparation work has been done in clean areas and 4-base pair 'tags' have been added to the DNA as soon as it is extracted so the Neanderthal DNA can be identified.

With 3 billion nucleotides sequenced, analysis of about ⅓ showed no sign of admixture between modern humans and Neanderthals, according to Pääbo. This concurred with the work of Noonan from two years earlier. The variant of microcephalin common outside Africa, which was suggested to be of Neanderthal origin and responsible for rapid brain growth in humans, was not found in Neanderthals. Nor was the MAPT variant, a very old variant found primarily in Europeans.

However, an analysis of a first draft of the Neanderthal genome by the same team released in May 2010 indicates interbreeding may have occurred. "Those of us who live outside Africa carry a little Neanderthal DNA in us," said Pääbo, who led the study. "The proportion of Neanderthal-inherited genetic material is about 1 to 4 percent. It is a small but very real proportion of ancestry in non-Africans today," says Dr. David Reich of Harvard Medical School, who worked on the study. This research compared the genome of the Neanderthals to five modern humans from China, France, sub-Saharan Africa, and Papua New Guinea. The finding is that about 1 to 4 percent of the genes of the non-Africans came from Neanderthals, compared to the baseline defined by the two Africans.

This indicates a gene flow from Neanderthals to modern humans, i.e., interbreeding between the two populations. Since the three non-African genomes show a similar proportion of Neanderthal sequences, the interbreeding must have occurred early in the migration of modern humans out of Africa, perhaps in the Middle East. No evidence for gene flow in the direction from modern humans to Neanderthals was found. The latter result would not be unexpected if contact occurred between a small colonizing population of modern humans and a much larger resident population of Neanderthals. A very limited amount of interbreeding could explain the findings, if it occurred early enough in the colonization process.

While interbreeding is viewed as the most parsimonious interpretation of the genetic discoveries, the authors point out they cannot conclusively rule out an alternative scenario, in which the source population of non-African modern humans was already more closely related to Neanderthals than other Africans were, due to ancient genetic divisions within Africa.

Among the genes shown to differ between present-day humans and Neanderthals were RPTN, SPAG17, CAN15, TTF1 and PCD16.

Extinction hypotheses

Neanderthal fossils found in Vindija Cave in Croatia have been dated to between 32,000 and 33,000 years old, and what have been claimed as the last traces of Mousterian culture (Neanderthal artefacts but not bones) have been found in Gorham's Cave on the remote south-facing coast of Gibraltar, dated to less than 30,000 years ago. However, a recent re-examination of Neanderthal bones from two Spanish Neanderthal sites has suggested they were around 45,000 years old, 10,000 years older than previously thought. Clive Finlayson, who excavated Gorham's Cave, argues that the sites which have been re-dated are highland ones which would have been inhospitable in the approach to an ice age. However bone collagen degrades in the warmer lowland sites where Finlayson thinks Neanderthals would have survived longer, and it has yet to be determined whether the re-dating affects other Neanderthal sites with reported recent dates.

Possible scenarios for the extinction of the Neanderthals are:

1. Neanderthals were a separate species from modern humans, and became extinct (due to climate change or interaction with humans) and were replaced by modern humans moving into their habitat beginning around 80,000 years ago. Competition with humans probably contributed to Neanderthal extinction. Jared Diamond has suggested a scenario of violent conflict and displacement.
2. Neanderthals were a contemporary subspecies that bred with modern humans and disappeared through absorption ( interbreeding theory).
3. A Campanian ignimbrite volcanic super-eruption around 40,000 years ago, followed by a second one a few thousand years later, has been hypothesised as having contributed to the demise of the Neanderthal, based on evidence from Mezmaiskaya cave in the Caucasus Mountains of southern Russia Mitochondrial DNA (mtDNA) analysis of a specimen from Mezmaiskaya Cave is radiocarbon dated to be about 29,000 years BP and therefore from one of the latest living Neanderthal individuals. The sequence shows 3.48% divergence from the Feldhofer Neanderthal. Phylogenetic analysis places the two Neanderthals from the Caucasus and western Germany together in a clade that is distinct from modern humans, suggesting that their mtDNA types have not contributed to the modern human mtDNA pool.

As Paul Jordan notes: "A natural sympathy for the underdog and the disadvantaged lends a sad poignancy to the fate of the Neanderthal folk, however it came about." Jordan, though, does say that there was perhaps interbreeding to some extent, but that populations that remained totally Neanderthal were probably out-competed and marginalized to extinction by the Aurignacians.

Climate change

About 55,000 years ago, the weather began to fluctuate wildly from extreme cold conditions to mild cold and back in a matter of a few decades. Neanderthal bodies were well suited for survival in a cold climate—their barrel chests and stocky limbs stored body heat better than the Cro-Magnons. However, the rapid fluctuations of weather caused ecological changes to which the Neanderthals could not adapt; familiar plants and animals would be replaced by completely different ones within a lifetime. Neanderthals' ambush techniques would have failed as grasslands replaced trees. A large number of Neanderthals would have died during these fluctuations, which peaked about 30,000 years ago.

Studies on Neanderthal body structures have shown that they needed more energy to survive than any other species of hominid. Their energy needs were up to 100–350 calories more per day comparing to projected anatomically modern human males weighing 68.5 kg (151.0 lbs) and females 59.2 kg (130.5 lbs). When food became scarce, this difference may have played a major role in the Neanderthals' extinction.

Coexistence with H. sapiens sapiens

There is no longer certainty regarding the identity of the humans who produced the Aurignacian culture, even though the presumed westward spread of anatomically modern humans (AMHs) across Europe is still based on the controversial first dates of the Aurignacian. Currently, the oldest European anatomically modern Homo sapiens is represented by a robust modern-human mandible discovered at Peştera cu Oase (southwest Romania), dated to 34,000–36,000 years ago. Human skeletal remains from the German site of Vogelherd, so far regarded as the best association between anatomically modern Homo sapiens and Aurignacian culture, were revealed to represent intrusive Neolithic burials into the Aurignacian levels and subsequently all the key Vogelherd fossils are now dated to 3,900–5,000 years ago instead. As for now, the expansion of the first anatomically modern humans into Europe cannot be located by diagnostic and well-dated AMH fossils "west of the Iron Gates of the Danube" before 32,000 years ago.

Consequently, the exact nature of biological and cultural interaction between Neanderthals and other human groups between 50,000 and 30,000 years ago has been contested. A new proposal strives to resolve the issue by proposing the Gravettians rather than the Aurignacians as the anatomically modern humans who contributed to the Eurasian genetic pool after 30,000 years ago. Correspondingly, the human skull fragment found at the Elbe River bank at Hahnöfersand near Hamburg was once radiocarbon-dated to 36,000 years ago and seen as possible evidence for the intermixing of Neanderthals and anatomically modern humans. It is now dated to the more recent Mesolithic.

Interbreeding hypotheses

An alternative to extinction is that Neanderthals were absorbed into the Cro-Magnon population by interbreeding. This would be counter to strict versions of the Recent African Origin, since it would imply that at least part of the genome of Europeans would descend from Neanderthals.

The most vocal proponent of the hybridization hypothesis is Erik Trinkaus of Washington University. Trinkaus claims various fossils as products of hybridized populations, including the "child of Lagar Velho", a skeleton found at Lagar Velho in Portugal dated to about 24,000 years ago. In a 2006 publication co-authored by Trinkaus, the fossils found in 1952 in the cave of Peștera Muierii, Romania, are likewise claimed as descendants of previously hybridized populations.

Genetic research has confirmed that some admixture took place. The genomes of all non-Africans include portions that are of Neanderthal origin, due to interbreeding between Neanderthals and the ancestors of Eurasians in Northern Africa or the Middle East prior to their spread. Rather than absorption of the Neanderthal population, this gene flow appears to have been of limited duration and limited extent. An estimated 1 to 4 percent of the DNA in Europeans and Asians (French, Chinese and Papua probands) is non-modern, and shared with ancient Neanderthal DNA rather than with Sub-Saharan Africans (Yoruba and San probands). Nonetheless, more recent genetic studies seem to suggest that modern humans may have mated with "at least two groups" of ancient humans: Neanderthals and Denisovans.

While modern humans share some nuclear DNA with the extinct Neanderthals, the two species do not share any mitochondrial DNA, which in primates is always maternally transmitted. This observation has prompted the hypothesis that whereas female humans interbreeding with male Neanderthals were able to generate fertile offspring, the progeny of female Neanderthals who mated with male humans were either rare, absent or sterile.

Specimens

• Neanderthal 1: Initial Neanderthal specimen found during an archaeological dig in August 1856. Discovered in a limestone quarry at the Feldhofer grotto in Neanderthal, Germany. The find consisted of a skull cap, two femora, the three right arm bones, two of the left arm bones, ilium, and fragments of a scapula and ribs.

• La Chapelle-aux-Saints 1: Called the Old Man, a fossilized skull discovered in La Chapelle-aux-Saints, France, by A. and J. Bouyssonie, and L. Bardon in 1908. Characteristics include a low vaulted cranium and large browridge typical of Neanderthals. Estimated to be about 60,000 years old, the specimen was severely arthritic and had lost all his teeth, with evidence of healing. For him to have lived on would have required that someone process his food for him, one of the earliest examples of Neanderthal altruism (similar to Shanidar I.)

• La Ferrassie 1: A fossilized skull discovered in La Ferrassie, France, by R. Capitan in 1909. It is estimated to be 70,000 years old. Its characteristics include a large occipital bun, low-vaulted cranium and heavily worn teeth.

• Le Moustier: A fossilized skull, discovered in 1909, at the archaeological site in Peyzac-le-Moustier, Dordogne, France. The Mousterian tool culture is named after Le Moustier. The skull, estimated to be less than 45,000 years old, includes a large nasal cavity and a somewhat less developed brow ridge and occipital bun as might be expected in a juvenile.

• Shanidar 1: Found in the Zagros Mountains in northern Iraq; a total of nine skeletons found believed to have lived in the Middle Paleolithic. One of the nine remains was missing part of its right arm; theorized to have been broken off or amputated. The find is also significant because it shows that stone tools were present among this tribe's culture. One was buried with flowers, showing that some type of burial ceremony may have occurred.

Chronology

Bones with Neanderthal traits in chronological order. (Sorted by time)

Mixed with H. heidelbergensis traits

• > 350 ka: Sima de los Huesos c. 500:350  ka ago
• 350–200 ka: Pontnewydd 225 ka ago.
• 200–135 ka: Atapuerca, Vértesszőlős, Ehringsdorf, Casal de'Pazzi, Biache, La Chaise, Montmaurin, Prince, Lazaret, Fontéchevade

Typical H. neanderthalensis traits

• 135–45 ka: Krapina, Saccopastore skulls, Malarnaud, Altamura, Gánovce, Denisova, Okladnikov Altai, Pech de l'Azé, Tabun 120 ka – 100±5 ka, Qafzeh9 100, Shanidar 1 to 9 80–60 ka, La Ferrassie 1 70 ka, Kebara 60 ka, Régourdou, Mt. Circeo, Combe Grenal, Erd 50 ka, La Chapelle-aux Saints 1 60 ka, Amud I 53±8 ka, Teshik-Tash.
• 45–35 ka: Le Moustier 45 ka, Feldhofer 42 ka, La Quina, l'Horus, Hortus, Kulna, Šipka, Saint Césaire, Bacho Kiro, El Castillo, Bñnolas, Arcy-sur-Cure.
• < 35 ka: Chătelperron, Figueria Brava, Zafaraya 30 ka, Vogelherd 3?, Vindija 32,400 ± 800 14C B.P. (Vi-208 31,390 ± 220, Vi-207 32,400 ± 1,800 14C B.P.), Velika Pećina,

Homo sapiens with some neanderthal-like archaic traits

• < 35 Pestera cu Oase 35 ka, Mladeč 31 ka, Pestera Muierii 30 ka (n/s), Lapedo Child 24.5 ka.

Neanderthal reconstructions

Early artistic reconstructions mostly presented Neanderthals as beastly creatures, emphasizing hairiness and rough, dark complexion.

More recent reconstructions acknowledge that due to the lineage evolution in European latitude there is reason to believe that Neanderthals were fair-skinned and probably with no more facial hair than modern man. Also, archaeological evidence exists indicating that they may have communicated by speech, used tools and engaged in artistic endeavours. Reconstructions of Neanderthal men, women and children have become much more intelligent-looking and pleasing to the modern eye.

Popular culture

Neanderthals have been portrayed in popular culture including appearances in literature, visual media and comedy, often in unflattering and inaccurate light.