Neanderthal (updated)

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Neanderthal Temporal range: Middle–Late Pleistocene 0.43/0.25–0.04 Ma PreЄ Є O S D C P T J K Pg N ↓
Late Neanderthal skull (La Chapelle-aux-Saints 1)
An approximate reconstruction of a Neanderthal skeleton. The central rib cage, including the sternum, and parts of the pelvis are from modern humans.
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Haplorhini
Infraorder:	Simiiformes
Family:	Hominidae
Subfamily:	Homininae
Tribe:	Hominini
Genus:	Homo
Species:	†H. neanderthalensis
Binomial name
†Homo neanderthalensis King, 1864
Known Neanderthal range in Europe (blue), Southwest Asia (orange), Uzbekistan (green), and the Altai mountains (violet).
Synonyms
Homo stupidus (Haeckel 1866) Homo mousteriensis (Klaatsch 1909) Palaeoanthropus neanderthalensis

Neanderthals, Homo neanderthalensis or Homo sapiens neanderthalensis) are an extinct species or subspecies of archaic humans in the genus Homo, who lived within Eurasia from circa 400,000 until 40,000 years ago.

Currently the earliest fossils of Neanderthals in Europe are dated between 450,000 and 430,000 years ago, and thereafter Neanderthals expanded into Southwest and Central Asia. They are known from numerous fossils, as well as stone tool assemblages. Almost all assemblages younger than 160,000 years are of the so-called Mousterian techno-complex, which is characterised by tools made out of stone flakes. The type specimen is Neanderthal 1, found in Neander Valley in the German Rhineland, in 1856.

Compared to modern humans, Neanderthals were stockier, with shorter legs and bigger bodies. In conformance with Bergmann's rule, as well as Allen's rule, this was likely was an adaptation to preserve heat in cold climates. Male and female Neanderthals had cranial capacities averaging 1,600 cm³ (98 cu in) and 1,300 cm³ (79 cu in), respectively, within the range of the values for anatomically modern humans. Average males stood around 164 to 168 cm (65 to 66 in) and females 152 to 156 cm (60 to 61 in) tall.

There has been growing evidence for admixture between Neanderthals and anatomically modern humans, reflected in the genomes of all modern non-African populations but not in the genomes of most sub-Saharan Africans. This suggests that interbreeding between Neanderthals and anatomically modern humans took place after the recent "out of Africa" migration, around 70,000 years ago. Recent admixture analyses have added to the complexity, finding that Eastern Neanderthals derived up to 2% of their ancestry from anatomically modern humans who left Africa some 100,000 years ago.

Name and classification

Neanderthals are named after one of the first sites where their fossils were discovered in the mid-19th century in the Neander Valley, just east of Düsseldorf, at the time in the Rhine Province of the Kingdom of Prussia (now in Northrhine-Westphalia, Germany). The valley itself was named for Joachim Neander, Neander being the graecicized form of the surname Neumann ("new man"). The German spelling of Thal "Valley" was current in the 19th century (contemporary German Tal).

Neanderthal 1 was known as the "Neanderthal cranium" or "Neanderthal skull" 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 group—was first proposed by the Anglo-Irish geologist William King in a paper read to the British Association in 1863, although in the following year he stated that the specimen was not human and rejected the name. King's name had priority over the proposal put forward in 1866 by Ernst Haeckel, Homo stupidus. Popular English usage of "Neanderthal" as shorthand for "Neanderthal man", as in "the Neanderthals" or "a Neanderthal", emerged in the popular literature of the 1920s.

Since the historical spelling -th- in German represents the phoneme /t/ or /tʰ/, not the fricative /θ/, standard British pronunciation of "Neanderthal" is with /t/ (IPA: /niːˈændərtɑːl/). Because of the usual sound represented by digraph ⟨th⟩ in English, "Neanderthal" is also pronounced with the voiceless fricative /θ/, at least in "layman's American English" (as /niːˈændərθɔːl/).

The spelling Neandertal is occasionally seen in English, even in scientific publications. Since "Neanderthal", or "Neandertal", is a common name, there is no authoritative prescription on its spelling, unlike the spelling of the binominal name H. neanderthalensis, which is predicated by King 1864. The common name in German is always invariably Neandertaler (lit. "of the valley of Neander"), not Neandertal, but the spelling of the name of the Neander Valley itself (Neandertal vs. Neanderthal) has been affected by the species name, the names of the Neanderthal Museum and of Neanderthal station persisting with pre-1900 orthography.

Ever since the discovery of the Neanderthal fossils, expert opinion has been divided as to whether Neanderthals should be considered a separate species (Homo neanderthalensis) or a subspecies (Homo sapiens neanderthalensis) relative to modern humans. Pääbo (2014) described such "taxonomic wars" as unresolveable in principle, "since there is no definition of species perfectly describing the case." The question depends on the definition of Homo sapiens as a chronospecies, which has also been in flux throughout the 20th century. Authorities preferring classification of Neanderthals as subspecies have introduced the subspecies name Homo sapiens sapiens for the anatomically modern Cro-Magnon population which lived in Europe at the same time as Neanderthals, while authorities preferring classification as separate species use Homo sapiens as equivalent to "anatomically modern humans".

During the early 20th century, a prevailing view of Neanderthals as "simian", influenced by Arthur Keith and Marcellin Boule, tended to exaggerate the anatomical differences between Neanderthals and Cro Magnon. Beginning in the 1930s, revised reconstructions of Neanderthals increasingly emphasized the similarity rather than differences from modern humans. From the 1940s throughout the 1970s, it was increasingly common to use the subspecies classification of Homo sapiens neanderthalensis vs. Homo sapiens sapiens. The hypothesis of "multiregional origin" of modern man was formulated in the 1980s on such grounds, arguing for the presence of an unbroken succession of fossil sites in both Europe and Asia. Hybridization between Neanderthals and Cro Magnon had been suggested on skeletal and craniological grounds since the early 20th century, and found increasing support in the later 20th century, until Neanderthal admixture was found to be present in modern populations genetics in the 2010s.

Evolution

Stage 1: Early pre-Neanderthal, possibly Homo erectus, (Tautavel Man, 450 ka)

 

Stage 2: Archaic Neanderthal (Miguelón, 430 ka)

 

Stage 3: Intermediate Neanderthal (Saccopastore I, 130 ka)

 

Stage 4: Classic European Neanderthal (La Chapelle-aux-Saints 1, 50 ka)

 

The evolution of Neanderthals according to the accretion model.

Both Neanderthals and anatomically modern humans were initially thought to have evolved from Homo erectus between 300,000 and 200,000 years ago. H. erectus had emerged around 1.8 million years ago, and had long been present, in various subspecies throughout Eurasia.

The divergence time between the Neanderthal and archaic Homo sapiens lineages is estimated to be between 800,000 and 400,000 years ago. The more recent time depth has been suggested by Endicott et al. (2010) and Rieux et al. (2014).

The time of divergence between archaic Homo sapiens and ancestors of Neanderthals and Denisovans caused by a population bottleneck of the latter was dated at 744,000 years ago, combined with repeated early admixture events and Denisovans diverging from Neanderthals 300 generations after their split from Homo sapiens, was calculated by Rogers et al. (2017).

Homo heidelbergensis, dated 600,000 to 300,000 years ago, has long been thought to be a likely candidate for the last common ancestor of the Neanderthal and modern human lineages. However, genetic evidence from the Sima de los Huesos fossils published in 2016 seems to suggest that H. heidelbergensis in its entirety should be included in the Neanderthal lineage, as "pre-Neanderthal" or "early Neanderthal", while the divergence time between the Neanderthal and modern lineages has been pushed back to before the emergence of H. heidelbergensis, to about 600,000 to 800,000 years ago, the approximate age of Homo antecessor.

The taxonomic distinctions between H. heidelbergensis and Neanderthals is mostly due to a fossil gap in Europe between 300,000 and 243,000 years ago (MIS 8). "Neanderthals", by conventions, are fossils which date to after this gap. The quality of the fossil record greatly increases from 130,000 years ago onwards. Specimens younger than this date make up the bulk of known Neanderthal skeletons and were the first whose anatomy was comprehensively studied. In morphological studies, the term "classic Neanderthal" may be used in a narrower sense for Neanderthals younger than 71,000 years old (MIS 4 and 3).

Microbiome

Neanderthals lived along-side humans until their extinction between 40,000-30,000 years ago, and share a common ancestor which could tell us more about how our microbiome evolved. Using dental calculus, calcified bone that traps microorganism, researchers have been able to look into how ancient human microbiomes may have existed. Based on a 16s shotgun sequence of dental calculus found in neanderthal specimens, researchers have found a large portion of neanderthal oral microbiome contains Actinobacteria, Firmicutes, Bacteroidetes, Proteobacteria, much like modern humans; however, neanderthals also had, Euryarchaeota, fungi and some oral pathogens that modern humans lack.

Diet of neanderthals depend on the environment they live in. Neanderthal remains recovered from Spy Cave, Belgium and examined them using dental calculus which indicated neanderthals in this area had meat based diet, including woolly rhinoceros and wild sheep. This is compared to neanderthal remains found in Spain. In El Sidrón Cave, Spain, they examined remains indicating a large amount of plant material such as nuts and moss, as well as mushrooms. Researchers determined that the difference in diets contributed to the neanderthal microbiota, and meat based diet caused the most variation. According to fecal biomarkers, neanderthals were able to convert cholesterol to coprostanol at a high rate, much like modern humans, because of the bacteria present in their gut.

Habitat and range

Approximate Neanderthal range; pre-Neanderthal and early Neanderthal range shown in magenta, late Neanderthal range in blue.

 

Sites where "classic Neanderthal" fossils (70–40 ka) have been found. Ice sheets of the last glacial maximum are indicated (partly ice-free during the Eemian interglacial)

 

Early Neanderthals, living before the Eemian interglacial (130 ka), are poorly known and come mostly from European sites. From 130 ka onwards, the quality of the fossil record increases dramatically. From then on, Neanderthal remains are found in Western, Central, Eastern, and Mediterranean Europe, as well as Southwest, Central, and Northern Asia up to the Altai Mountains in Siberia. No Neanderthal has ever been found outside Central to Western Eurasia, namely neither to the south of 30°N (Shuqba, Levant), nor east of 85°E (Denisova, Siberia).

The limit of their northern range appears to have been south of 53°N (Bontnewydd, Wales), although it is difficult to assess because glacial advances destroy most human remains, the Bontnewydd tooth being exceptional. Middle Palaeolithic artefacts have been found up to 60°N on the Russian plains.

Total Neanderthal effective population size has been estimated at close to 15,000 individuals (corresponding to a total population of roughly 150,000 individuals), living in small, isolated, inbred groups.

Anatomy

Anatomical comparison of skulls of Homo sapiens (Oase 1, left) and Homo neanderthalensis (right)
(Cleveland Museum of Natural History).

Features compared are the braincase shape, forehead, browridge, nasal bone projection, cheek bone angulation, chin and occipital contour.

 

Comparison of faces of early European Homo sapiens (left) and Homo neanderthalensis (right) based on forensic facial reconstructions exhibited at the Neanderthal Museum.

 

Neanderthal anatomy differed from modern humans in that they had a more robust build and distinctive morphological features, especially on the cranium, which gradually accumulated more derived aspects as it was described by Marcellin Boule, particularly in certain isolated geographic regions. These include shorter limb proportions, a wider, barrel-shaped rib cage, a reduced chin, sloping forehead, and a large nose, being at the modern human higher end in both width and length, and started somewhat higher on the face than in modern humans. The Neanderthal skull is typically more elongated and less globular than that of anatomically modern humans, and features a notable occipital bun. Inherited Neanderthal DNA variants may subtly influence the skull shape of living people.

Neanderthals were much stronger than modern humans, with particularly strong arms and hands, while they were comparable in height; based on 45 long bones from 14 males and 7 females, three different methods of estimating height produced averages for Neanderthal males from 164 to 168 cm (65 to 66 in) and 152 to 156 cm (60 to 61 in) for females. Samples of 26 specimens found an average weight of 77.6 kg (171 lb) for males and 66.4 kg (146 lb) for females.

Neanderthals are known for their large cranial capacity, which at 1,600 cm³ (98 cu in) is larger on average than that of modern humans. One study has found that drainage of the dural venous sinuses (low pressure blood vessels that run between the meninges and skull leading down through the skull) in the occipital lobe region of Neanderthal brains appears more asymmetric than other hominid brains. Three-dimensional computer-assisted reconstructions of Neanderthal infants based on fossils from Russia and Syria indicated that Neanderthal and modern human brains were the same size at birth, but that by adulthood, the Neanderthal brain was larger than the modern human brain. They had almost the same degree of encephalisation (i.e. brain-to-body-size ratio) as modern humans.

Three-dimensional reconstructions of nasal cavities and computational fluid dynamics techniques have found that Neanderthals and modern humans both adapted their noses (independently and in a convergent way) to help breathe in cold and dry conditions. The large nose seen in Neanderthals, as well as Homo heidelbergensis, affected the shape of the skull and the muscle attachments, and gave them a weaker bite force than in modern humans. Larger eye sockets and larger areas of the brain devoted to vision suggest that their eyesight may have been better than that of modern humans. Dental remains from two Italian sites indicate that Neanderthal dental features had evolved by around 450,000 years ago during the Middle Pleistocene epoch.

Two Neanderthal specimens from Italy and Spain were found to have an allele of the melanocortin 1 receptor (MC1R) with reduced activity. This receptor plays a role in mammalian pigmentation, and the activity of the novel allele in Neanderthals was found to be reduced sufficiently to allow for visibly lighter pigment expression. Although not found in the small European sample studied by Lalueza et al., a larger study found that the derived variant was present at 70% frequency in Taiwanese Aborigines, 50% frequency in Cheyenne Native Americans, 30% frequency in Han Chinese, and 5% frequency in Europeans.  It is therefore unclear whether this loss-of-function variant is responsible for any other traits other than lightening the skin (such as red or blonde hair). This allele was not found in the Croatian or Altai Neanderthal specimens subjected to whole-genome sequencing, nor have the MC1R variants known to cause red hair in modern humans, though the Altai specimen was polymorphic for another variant MC1R allele of unknown effect. Genomic analysis of three Croatian specimens for the alleles of numerous genes that affect pigment in modern humans showed the Neanderthals to have more dark-pigment-producing alleles than those producing reduced pigmentation. Based on this they concluded these Neanderthals had darker hair, skin and eye coloration than modern Europeans. Skin pigmentation prediction for archaic humans is a controversial field, as there are no living samples to confirm or identify novel SNPs.

 

The overall shorter limbs and in general more stout body proportions of Neanderthals may have been an adaptation to colder climates. In comparison to modern humans, Neanderthals were more suited for sprinting and pouncing activities rather than endurance running, which would have been adaptive in the forests and woodlands that seem to have been their preferred environment. Genomic evidence possibly points to a higher proportion of fast-twitch muscle fiber in the Neanderthal. Evidence suggests that Neanderthals walked upright much like modern humans.

Behaviour

Levallois point – Beuzeville, France

Neanderthals made stone tools, used fire, and were hunters. This is the extent of the consensus on their behaviour. It had long been debated whether Neanderthals were hunters or scavengers, but the discovery of the pre-Neanderthal Schöningen wooden spears in Germany helped settle the debate in favour of hunting. A Levallois point embedded in the vertebrae of a wild ass indicated that a javelin had been thrown with a parabolic trajectory to disable the animal. Most available evidence suggests they were apex predators, and fed on red deer, reindeer, ibex, wild boar, aurochs and on occasion mammoth, straight-tusked elephant and rhinoceros. They appear to have occasionally used vegetables as fall-back food, revealed by isotope analysis of their teeth and study of their coprolites (fossilised faeces). Dental analysis of specimens from Spy, Belgium and El Sidrón, Spain suggested that these Neanderthals had a wide-ranging diet, with no evidence at all that the El Sidrón Neanderthals were carnivorous, instead living on "a mixture of forest moss, pine nuts and a mushroom known as split gill". Nonetheless, isotope studies of Neanderthals from two French sites showed similar profiles to other carnivores, suggesting that these populations may have eaten meat. The Neanderthal skeleton suggests they consumed 100 to 350 kcal (420 to 1,460 kJ) more per day than modern male humans of 68.5 kg (151 lb) and females of 59.2 kg (131 lb).

The size and distribution of Neanderthal sites, along with genetic evidence, suggests Neanderthals lived in much smaller and more sparsely distributed groups than anatomically-modern Homo sapiens. The bones of twelve Neanderthals were discovered at El Sidrón cave in northwestern Spain. They are thought to have been a group killed and butchered about 50,000 years ago. Analysis of the mtDNA showed that the three adult males belonged to the same maternal lineage, while the three adult females belonged to different ones. This suggests a social structure where males remained in the same social group and females "married out".

The bones of the El Sidrón group show signs of defleshing, suggesting that they were victims of cannibalism. The St. Césaire 1 skeleton from La Roche à Pierrot, France, showed a healed fracture on top of the skull apparently caused by a deep blade wound, suggesting interpersonal violence. Shanidar 3, an adult male dated to the late middle Paleolithic, was found to have a rib lesion characteristic of projectile weapon injuries, which some anthropologists consider evidence for interspecies conflict.

Neanderthals suffered a high rate of traumatic injury, with by some estimates 79% of specimens showing evidence of healed major trauma. It was thus theorized that Neanderthals employed a riskier and possibly less sophisticated hunting strategy. However, rates of cranial trauma are not significantly different between Neanderthal and middle paleolithic Anatomically Modern Human samples. Both populations evidently cared for the injured and had some degree of medical knowledge. 

Claims that Neanderthals deliberately buried their dead, and if they did, whether such burials had any symbolic meaning, are heavily contested. The debate on deliberate Neanderthal burials has been active since the 1908 discovery of the well-preserved Chapelle-aux-Saints 1 skeleton in a small hole in a cave in southwestern France. In this controversy's most recent installment, a team of French researchers reinvestigated the Chapelle-aux-Saints cave and in January 2014 reasserted the century-old claim that the 1908 Neanderthal specimen had been deliberately buried, and this has in turn been heavily criticised.

According to archaeologist John F. Hoffecker:

Neanderthal sites show no evidence of tools for making tailored clothing. There are only hide scrapers, which might have been used to make blankets or ponchos. This is in contrast to Upper Paleolithic (modern human) sites, which have an abundance of eyed bone needles and bone awls. Moreover, microwear analysis of Neanderthal hide scrapers shows that they were used only for the initial phases of hide preparation, and not for the more advanced phases of clothing production.

— John F. Hoffecker, The Spread of Modern Humans in Europe

Culture

Whether Neanderthals created art and used adornments, which would indicate a capability for complex symbolic thought, remains unresolved. A 2010 paper on radiocarbon dates cast doubt on the association of Châtelperronian beads with Neanderthals, and Paul Mellars considered the evidence for symbolic behaviour to have been refuted. This conclusion, however, is controversial, and others such as Jean-Jacques Hublin and colleagues have re-dated material associated with the Châtelperronian artifacts and used proteomic evidence to restate the challenged association with Neanderthals.

Artist's reconstruction of a Neanderthal man with child

 

A large number of other claims of Neanderthal art, adornment, and structures have been made. These are often taken by the media as showing Neanderthals were capable of symbolic thought, or were "mental equals" to anatomically modern humans. As evidence of symbolism, none of them are widely accepted, although the same is true for Middle Palaeolithic anatomically modern humans. Among many others:

• Flower pollen on the body of pre-Neanderthal Shanidar 4, Iraq, had in 1975 been argued to be a flower burial. Once popular, this theory is no longer accepted.
• Bird bones were argued to show evidence for feather plucking in a 2012 study examining 1,699 ancient sites across Eurasia, which the authors controversially took to mean Neanderthals wore bird feathers as personal adornments.
• Deep scratches were found in 2012 on a cave floor underlying Neanderthal layer in Gorham's Cave, Gibraltar, which some have controversially interpreted as art.
• Two 176,000-year-old stalagmite ring structures, several metres wide, were reported in 2016 more than 300 metres from the entrance within Bruniquel Cave, France. The authors claim artificial lighting would have been required as this part of the cave is beyond the reach of daylight and that the structures had been made by early Neanderthals, the only humans in Europe at this time.
• In 2015, a study argued that a number of 130,000-year-old eagle talons found in a cache near Krapina, Croatia along with Neanderthal bones, had been modified to be used as jewellery.

All of these appeared only in single locations. Yet in 2018, using uranium-thorium dating methods, red painted symbols comprising a scalariform (ladder shape), a negative hand stencil, and red lines and dots on the cave walls of three Spanish caves 700 km (430 mi) apart were dated to at least 64,000 years old. If the dating is correct, they were painted before the time anatomically modern humans are thought to have arrived in Europe. Paleoanthropologist John D. Hawks argues these findings demonstrate Neanderthals were capable of symbolic behaviour previously thought to be unique to modern humans.

Interbreeding with archaic and modern humans

Chris Stringer's hypothesis of the family tree of genus Homo, published 2012 in Nature – the horizontal axis represents geographic location, and the vertical axis represents time in millions of years ago.

 

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 theory, since it would imply that at least part of the genome of Europeans would descend from Neanderthals.

Pre-2010 interbreeding hypotheses

Until the early 1950s, most scholars thought Neanderthals were not in the ancestry of living humans. Nevertheless, Thomas H. Huxley in 1904 saw among Frisians the presence of what he suspected to be Neanderthaloid skeletal and cranial characteristics as an evolutionary development from Neanderthal rather than as a result of interbreeding, saying that "the blond long-heads may exhibit one of the lines of evolution of the men of the Neanderthaloid type," yet he raised the possibility that the Frisians alternatively "may be the result of the admixture of the blond long-heads with Neanderthal men," thus separating "blond" from "Neanderthaloid."

Hans Peder Steensby proposed interbreeding in 1907 in the article Race studies in Denmark. He strongly emphasised that all living humans are of mixed origins. He held that this would best fit observations, and challenged the widespread idea that Neanderthals were ape-like or inferior. Basing his argument primarily on cranial data, he noted that the Danes, like the Frisians and the Dutch, exhibit some Neanderthaloid characteristics, and felt it was reasonable to "assume something was inherited" and that Neanderthals "are among our ancestors." 

Carleton Stevens Coon in 1962 found it likely, based upon evidence from cranial data and material culture, that Neanderthal and Upper Paleolithic peoples either interbred or that the newcomers reworked Neanderthal implements "into their own kind of tools." Christopher Thomas Cairney in 1989 went further, laying out a rationale for hybridisation and adding a broader discussion of physical characteristics as well as commentary on interbreeding and its importance to adaptive European phenotypes. Cairney specifically discussed the "intermixture of racial elements" and "hybridisation."

By the early 2000s, the majority of scholars supported the Out of Africa hypothesis, according to which anatomically modern humans left Africa about 50,000 years ago and replaced Neanderthals with little or no interbreeding. Yet some scholars still argued for hybridisation with Neanderthals. The most vocal proponent of the hybridisation hypothesis was Erik Trinkaus of Washington University. Trinkaus claimed various fossils as products of hybridised populations, including the skeleton of a child found at Lagar Velho in Portugal and the Peștera Muierii skeletons from Romania.

Genetic evidence

In 2010, geneticists announced that interbreeding had likely taken place, a result confirmed in 2012. The genomes of all non-Africans include portions that are of Neanderthal origin, a share estimated in 2014 to 1.5–2.1%. This DNA is absent in Sub-Saharan Africans (Yoruba people and San subjects). Ötzi the iceman, Europe's oldest preserved mummy, was found to possess an even higher percentage of Neanderthal ancestry. The two percent of Neanderthal DNA in Europeans and Asians is not the same in all Europeans and Asians: in all, approximately 20% of the Neanderthal genome appears to survive in the modern human gene pool.

Genomic studies suggest that modern humans mated with at least two groups of archaic humans: Neanderthals and Denisovans. Some researchers suggest admixture of 3.4–7.9% in modern humans of non-African ancestry, rejecting the hypothesis of ancestral population structure. Detractors have argued and continue to argue that the signal of Neanderthal interbreeding may be due to ancient African substructure, meaning that the similarity is only a remnant of a common ancestor of both Neanderthals and modern humans and not the result of interbreeding. John D. Hawks has argued that the genetic similarity to Neanderthals may indeed be the result of both structure and interbreeding, as opposed to just one or the other.

An approximately 40,000 year old anatomically-modern human skeleton from Peștera cu Oase, Romania, was found in 2015 to have a much larger proportion of DNA matching the Neanderthal genome than seen in humans of today, and this was estimated to have resulted from an interbreeding event as few as four generations earlier. However, this hybrid Romania population does not appear to have made a substantial contribution to the genomes of later Europeans.

While some modern human nuclear DNA has been linked to the extinct Neanderthals, no mitochondrial DNA of Neanderthal origin has been detected, which in primates is almost 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.

However, Eastern Neanderthals derive significant portions of their ancestry from an earlier dispersal of modern humans unrelated to the one that gave rise to Eurasians today. It is estimated that they split off shortly after the Khoisan divergence some 200 kya. Such unidirectional flow is significant given the current scenario of no Eurasian admixture in Western European Neanderthals. This is not contradictory to the Out-of-Africa model, which claims a single-dispersal to give rise to all Eurasians today. A signal of an early dispersal is present in the genome of New Guineans, who derive up to 2% of their ancestry from this group that apparently diverged from other Africans 120 kya. However, it is noted that the Denisovans do not carry this early human dispersal signal. Pagani et al. therefore argue that the admixture between this early modern human group, modern Eurasians, and Neanderthals took place in Southern Arabia or the Levant and that the latter group consisted of migrants from the Middle East into Siberia.

Interbreeding with Denisovans

Sequencing of the genome of a Denisovan, a distinct but related archaic hominin, from the Denisova cave in the Siberian Altai region has shown that 17% of its genome represents Neanderthal DNA. Unsurprisingly, the genome from a 120,000 year old Neanderthal bone found in the same cave more closely resembled the Neanderthal DNA present in the Denisovan genome than that of Neanderthals from the Vindija cave in Croatia or the Mezmaiskaya cave in the Caucasus, suggesting that the gene flow came from a local interbreeding. However, the complete genome sequencing of DNA from a 90,000 year old bone fragment, Denisova 11, showed it to have belonged to a Denisovan-Neanderthal hybrid, whose father was a typical Denisovan with the Altai Neanderthal component dating to an interbreeding more than 300 generations earlier, but the specimen's mother was a Neanderthal belonging to a population more closely related to the Vindija Neanderthal than to the sequenced Altai Neanderthal genome. This suggests mobility or turnover among the distinct Neanderthal populations.

Extinction

According to a 2014 study by Thomas Higham and colleagues of organic samples from European sites, Neanderthals died out in Europe between 41,000 and 39,000 years ago. New dating in Iberia, where Neanderthal dates as late as 24,000 years had been reported before, now suggests evidence of Neanderthal survival in the peninsula after 42,000 years ago is almost non-existent.

Anatomically modern humans arrived in Mediterranean Europe between 45,000 and 43,000 years ago, so the two different human populations shared Europe for several thousand years. The exact nature of biological and cultural interaction between Neanderthals and other human groups is contested.

Possible scenarios for the extinction of the Neanderthals are:

1. Neanderthals were a separate species from modern humans, and became extinct (because of climate change or interaction with modern humans) and were replaced by modern humans moving into their habitat between 45,000 and 40,000 years ago. 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. Volcanic catastrophe: see Campanian Ignimbrite Eruption

mtDNA-based simulation of modern human expansion in Europe starting 1,600 generations ago. Neanderthal range in light grey

Climate change

About 55,000 years ago, the climate began to fluctuate wildly from extreme cold conditions to mild cold and back in a matter of decades. Neanderthal bodies were well-suited for survival in a cold climate—their stocky chests and limbs stored body heat better than the Cro-Magnons. Neanderthals died out in Europe between 41,000 and 39,000 years ago, coinciding with the start of a very cold period.

Raw material sourcing and the examination of faunal remains found in the southern Caucasus suggest that modern humans may have had a survival advantage, being able to use social networks to acquire resources from a greater area. In both the Late Middle Palaeolithic and Early Upper Palaeolithic more than 95% of stone artifacts were drawn from local material, suggesting Neanderthals restricted themselves to more local sources.

Coexistence with modern humans

Skeleton and restoration model of the La Ferrassie 1 Neanderthal man (National Museum of Nature and Science, Tokyo, 2013 photograph)

 

In November 2011 tests conducted at the Oxford Radiocarbon Accelerator Unit in England on what were previously thought to be Neanderthal baby teeth, which had been unearthed in 1964 from the Grotta del Cavallo in Italy, were identified as the oldest modern human remains discovered anywhere in Europe, dating from between 43,000 and 45,000 years ago. Given that the 2014 study by Thomas Higham of Neanderthal bones and tools indicates that Neanderthals died out in Europe between 41,000 and 39,000 years ago, the two different human populations shared Europe for as long as 5,000 years. Nonetheless, the exact nature of biological and cultural interaction between Neanderthals and other human groups has been contested.

Modern humans co-existed with them in Europe starting around 45,000 years ago and perhaps even earlier. Neanderthals inhabited that continent long before the arrival of modern humans. These modern humans may have introduced a disease that contributed to the extinction of Neanderthals, and that may be added to other recent explanations for their extinction. When Neanderthal ancestors left Africa potentially as early as over 800,000 years ago they adapted to the pathogens in their European environment, unlike modern humans, who adapted to African pathogens. This transcontinental movement is known as the Out of Africa model. If contact between humans and Neanderthals occurred in Europe and Asia the first contact may have been devastating to the Neanderthal population, because they would have had little, if any, immunity to the African pathogens. More recent historical events in Eurasia and the Americas show a similar pattern, where the unintentional introduction of viral or bacterial pathogens to unprepared populations has led to mass mortality and local population extinction. The most well-known example of this is the arrival of Christopher Columbus to the New World, which brought and introduced foreign diseases when he and his crew arrived to a native population who had no immunity. 

Anthropologist Pat Shipman, of Pennsylvania State University, suggested that domestication of the dog could have played a role in Neanderthals' extinction.

History of research

Engis 2, child (1829)

 

Gibraltar 1, female (1848)

 

Neanderthal 1, male (upper skull 1856, left-cheek 2000)

 

Spy 2 skull, sex unclear (1886)

 

Krapina 3, female (1899)

 

Neanderthal fossils were first discovered in 1829 in the Engis caves (the partial skull dubbed Engis 2), in what is now Belgium by Philippe-Charles Schmerling and the Gibraltar 1 skull in 1848 in the Forbes' Quarry, Gibraltar. These finds were not, at the time, recognized as representing an archaic form of humans.

The first discovery which was recognized as representing an archaic form of humans was made in August 1856, three years before Charles Darwin's On the Origin of Species was published. This was the discovery of the type specimen, Neanderthal 1, in a limestone quarry (Feldhofer Cave), located in Neandertal Valley in the German Rhineland, about 12 km (7 mi) east of Düsseldorf). The find consisted of a skull cap, two femora, three bones of the right arm, two of the left arm, parts of the left ilium, fragments of a scapula, and ribs. The workers who recovered the objects originally thought them to be the remains of a cave bear. However, they eventually gave the material to amateur naturalist Johann Carl Fuhlrott, who turned the fossils over to anatomist Hermann Schaaffhausen.

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

• 1829: A damaged skull of a Neanderthal child, Engis 2, is discovered in Engis, Netherlands (now Belgium).
• 1848: A female Neanderthal skull, Gibraltar 1, is found in Forbes' Quarry, Gibraltar, but its importance is not recognised.
• 1856: Limestone miners discover the Neanderthal-type specimen, Neanderthal 1, in Neandertal, western Prussia (now Germany).
• 1864: William King is the first to recognise Neanderthal 1 as belonging to a separate species, for which he gives the scientific name Homo neanderthalensis. He then changed his mind on placing it in the genus Homo, arguing that the upper skull was different enough to warrant a separate genus since, to him, it had likely been "incapable of moral and theistic conceptions."
• 1880: The mandible of a Neanderthal child is discovered in a secure context in Šipka cave, in the Austro-Hungarian Empire (now the Czech Republic), associated with cultural debris, including hearths, Mousterian tools, and bones of extinct animals.
• 1886: Two well-preserved Neanderthal skeletons are found at Spy, Belgium, making the hypothesis that Neanderthal 1 was only a diseased modern human difficult to sustain.
• 1899: Sand excavation workers find hundreds of fragmentary Neanderthal remains representing at least 12 and likely as much as 70 individuals on a hill in Krapina, in the Austro-Hungarian Empire (now Croatia).
• 1908: A very well preserved Neanderthal, La Chapelle-aux-Saints 1, is found in its eponymous site in France, said by the excavators to be a burial, a claim still heatedly contested. For historical reasons it remains the most famous Neanderthal skeleton.
• 1912: Marcellin Boule publishes his now discredited influential study of Neanderthal skeletal morphology based on La Chapelle-aux-Saints 1.
• 1953–1957: Ten Neanderthal skeletons are excavated in Shanidar Cave, Iraqi Kurdistan, by Ralph Solecki and colleagues.
• 1975: Erik Trinkaus's study of Neanderthal feet strongly argues that Neanderthals walked like modern humans.
• 1981: The site of Bontnewydd, Wales yielded an early Neanderthal tooth, the most north-western Neanderthal remain ever.
• 1987: Israeli Neanderthal Kebara 2 is dated (by TL and ESR) to 60,000 BP, thus later than the Israeli anatomically modern humans dated to 90,000 and 80,000 BP at Qafzeh and Skhul.
• 1997: Matthias Krings et al. are the first to amplify Neanderthal mitochondrial DNA (mtDNA) using a specimen from Feldhofer grotto in the Neander valley.
• 2005: The Max Planck Institute for Evolutionary Anthropology and associated institutions launch the Neanderthal genome project to sequence the Neanderthal nuclear genome.
• 2010: Discovery of Neanderthal admixture in the genome of modern populations.
• 2014: A comprehensive dating of Neanderthal bones and tools from hundreds of sites in Europe dates the disappearance of Neanderthals to 41,000 and 39,000 years ago.
• 2018: Report on the complete genomic sequence of Denisova 11, a first generation of Neanderthal-Denisovan hybrid.

Specimens

Notable European Neanderthals

Remains of more than 300 European Neanderthals have been found.

• Neanderthal 1: The first human bones recognised as showing a non-modern anatomy. Discovered in 1856 in a limestone quarry at the Feldhofer grotto in Neanderthal, Germany, they consist of a skull cap, the two femora, the three right arm bones, two left arm bones, the ilium, and fragments of a scapula and ribs.
• La Chapelle-aux-Saints 1: Called the Old Man, a fossilised 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 long before death, leading some to suggest he was cared for by others.
• La Ferrassie 1: A fossilised 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 1: One of the rare nearly complete Neanderthal skeletons to be discovered, it was excavated by a German team in 1908, at Peyzac-le-Moustier, France. Sold to a Berlin museum, the post cranial skeleton was bombed and mostly destroyed in 1945, and parts of the mid face were lost sometime after then. The skull, estimated to be less than 45,000 years old, includes a large nasal cavity and a less developed brow ridge and occipital bun than seen in other Neanderthals. The Mousterian tool techno-complex is named after its discovery site.

Notable Southwest Asian Neanderthals

Remains of more than 70 Southwest Asian Neanderthals have been found.

• Shanidar 1 to 10: Eight Neanderthals and two pre-Neanderthals (Shanidar 2 and 4) were discovered in the Zagros Mountains in Iraqi Kurdistan. One of the skeletons, Shanidar 4, was once thought to have been buried with flowers, a theory no longer accepted. To Paul B. Pettitt the "deliberate placement of flowers has now been convincingly eliminated", since "[a] recent examination of the microfauna from the strata into which the grave was cut suggests that the pollen was deposited by the burrowing rodent Meriones tersicus, which is common in the Shanidar microfauna and whose burrowing activity can be observed today".
• Amud 1: A male adult Neanderthal, dated to roughly 55,000 BP, and one of several found in a cave at Nahal Amud, Israel. At 178 cm (70 in), it is the tallest known Neanderthal. It also has the largest cranial capacity of all extinct hominins: 1,736 cm³.
• Kebara 2: A male adult post-cranial skeleton, dated to roughly 60,000 BP, that was discovered in 1983 in Kebara Cave, Israel. It has been studied extensively, for its hyoid, ribcage, and pelvis are much better preserved than in all other Neanderthal specimens.

Notable Central Asian Neanderthal

• Teshik-Tash 1: An 8–11-year-old skeleton discovered in Uzbekistan by Okladnikov in 1938. This is the only fairly complete skeleton discovered to the east of Iraq. Okladnikov claimed it was a deliberate burial, but this is debated.

Chronology

This section describes bones with Neanderthal traits in chronological order.

Mixed with H. heidelbergensis traits

• older than 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

H. neanderthalensis fossils

• 130–50 ka: Krapina, Saccopastore skulls, Malarnaud, Altamura, Gánovce, Denisova, Okladnikov, Pech de l'Azé, Tabun 120–100±5 ka, 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.
• In radiocarbon range, > 50 ka: Le Moustier, Feldhofer, La Quina, l'Hortus, Kulna, Šipka, Saint Césaire, Bacho Kiro, El Castillo, Bañolas, El Sidrón (48±3 cal ka), Arcy-sur-Cure, Châtelperron, Figueira Brava, Mezmaiskaya (41±1 cal ka), Zafarraya, Vindija, Velika Pećina.

H. s. sapiens with traits reminiscent of Neanderthals

• younger than 35 Peștera cu Oase 37-42 ka, Mladeč 31 ka, Pestera Muierii 30 ka (n/s), Lagar Velho 1 24.5 ka.

In popular culture

Neanderthals have been portrayed in popular culture including appearances in literature, visual media and comedy. Early 20th century artistic interpretations often presented Neanderthals as beastly creatures, emphasising hairiness and a rough, dark complexion.

Personality psychology

From Wikipedia, the free encyclopedia

A picture of the depictions of personality dimensions.

 

Personality psychology is a branch of psychology that studies personality and its variation among individuals. It is a scientific study which aims to show how people are individually different due to psychological forces. Its areas of focus include:

• Construction of a coherent picture of the individual and their major psychological processes;
• Investigation of psychological differences;
• Investigation of human nature and psychological similarities between individuals.

"Personality" is a dynamic and organized set of characteristics possessed by a person that uniquely influences their environment, cognitions, emotions, motivations, and behaviors in various situations. The word personality originates from the Latin persona, which means "mask". 

Personality also refers to the pattern of thoughts, feelings, social adjustments, and behaviors consistently exhibited over time that strongly influences one's expectations, self-perceptions, values, and attitudes. Personality also predicts human reactions to other people, problems, and stress. Gordon Allport (1937) described two major ways to study personality: the nomothetic and the idiographic. Nomothetic psychology seeks general laws that can be applied to many different people, such as the principle of self-actualization or the trait of extraversion. Idiographic psychology is an attempt to understand the unique aspects of a particular individual. 

The study of personality has a broad and varied history in psychology with an abundance of theoretical trad. The major theories include dispositional (trait) perspective, psychodynamic, humanistic, biological, behaviorist, evolutionary, and social learning perspective. However, many researchers and psychologists do not explicitly identify themselves with a certain perspective and instead take an eclectic approach. Research in this area is empirically driven, such as dimensional models, based on multivariate statistics, such as factor analysis, or emphasizes theory development, such as that of the psychodynamic theory. There is also a substantial emphasis on the applied field of personality testing. In psychological education and training, the study of the nature of personality and its psychological development is usually reviewed as a prerequisite to courses in abnormal psychology or clinical psychology.

Philosophical assumptions

Many of the ideas developed by historical and modern personality theorists stem from the basic philosophical assumptions they hold. The study of personality is not a purely empirical discipline, as it brings in elements of art, science, and philosophy to draw general conclusions. The following five categories are some of the most fundamental philosophical assumptions on which theorists disagree:

• Freedom versus determinism – This is the question whether humans have control over their own behavior and understand the motives behind it or if their behavior is causally determined by forces beyond their control. Behavior is categorized as being either unconscious, environmental or biological by various theories.
• Heredity (Nature) versus environment (Nurture) – Personality is thought to be determined largely either by genetics and biology, or by environment and experiences. Contemporary research suggests that most personality traits are based on the joint influence of genetics and environment. One of the forerunners in this arena is C. Robert Cloninger, who pioneered the Temperament and Character model.
• Uniqueness versus universality – This question discusses the extent of each human's individuality (uniqueness) or similarity in nature (universality). Gordon Allport, Abraham Maslow, and Carl Rogers were all advocates of the uniqueness of individuals. Behaviorists and cognitive theorists, in contrast, emphasize the importance of universal principles, such as reinforcement and self-efficacy.
• Active versus reactive – This question explores whether humans primarily act through individual initiative (active) or through outside stimuli. Traditional behavioral theorists typically believed that humans are passively shaped by their environments, whereas humanistic and cognitive theorists believe that humans are more active in their role. Most modern theorists agree that both are important, with aggregate behavior being primarily determined by traits and situational factors being the primary predictor of behavior in the short term.
• Optimistic versus pessimistic – Personality theories differ with regard to whether humans are integral in the changing of their own personalities. Theories that place a great deal of emphasis on learning are often more optimistic than those that do not.

Personality theories

Type theories

Personality type refers to the psychological classification of different types of people. Personality types are distinguished from personality traits, which come in different degrees. There are many types of theories regarding personality, but each theory contains several and sometimes many sub theories. A "theory of personality" constructed by any given psychologist will contain multiple relating theories or sub theories often expanding as more psychologists explore the theory. For example, according to type theories, there are two types of people, introverts and extroverts. According to trait theories, introversion and extroversion are part of a continuous dimension with many people in the middle. The idea of psychological types originated in the theoretical work of Carl Jung, specifically in his 1921 book Psychologische Typen (Psychological Types) and William Marston.

Building on the writings and observations of Jung during World War II, Isabel Briggs Myers and her mother, Katharine C. Briggs, delineated personality types by constructing the Myers–Briggs Type Indicator. This model was later used by David Keirsey with a different understanding from Jung, Briggs and Myers. In the former Soviet Union, Lithuanian Aušra Augustinavičiūtė independently derived a model of personality type from Jung's called socionics.

Theories could also be considered an "approach" to personality or psychology and is generally referred to as a model. The model is an older and more theoretical approach to personality, accepting extroversion and introversion as basic psychological orientations in connection with two pairs of psychological functions:

• Perceiving functions: sensing and intuition (trust in concrete, sensory-oriented facts vs. trust in abstract concepts and imagined possibilities)
• Judging functions: thinking and feeling (basing decisions primarily on logic vs. deciding based on emotion).

Briggs and Myers also added another personality dimension to their type indicator to measure whether a person prefers to use a judging or perceiving function when interacting with the external world. Therefore, they included questions designed to indicate whether someone wishes to come to conclusions (judgment) or to keep options open (perception).

This personality typology has some aspects of a trait theory: it explains people's behavior in terms of opposite fixed characteristics. In these more traditional models, the sensing/intuition preference is considered the most basic, dividing people into "N" (intuitive) or "S" (sensing) personality types. An "N" is further assumed to be guided either by thinking or feeling and divided into the "NT" (scientist, engineer) or "NF" (author, humanitarian) temperament. An "S", in contrast, is assumed to be guided more by the judgment/perception axis and thus divided into the "SJ" (guardian, traditionalist) or "SP" (performer, artisan) temperament. These four are considered basic, with the other two factors in each case (including always extraversion/introversion) less important. Critics of this traditional view have observed that the types can be quite strongly stereotyped by professions (although neither Myers nor Keirsey engaged in such stereotyping in their type descriptions), and thus may arise more from the need to categorize people for purposes of guiding their career choice. This among other objections led to the emergence of the five-factor view, which is less concerned with behavior under work conditions and more concerned with behavior in personal and emotional circumstances. (The MBTI is not designed to measure the "work self", but rather what Myers and McCaulley called the "shoes-off self.") 

Type A and Type B personality theory: During the 1950s, Meyer Friedman and his co-workers defined what they called Type A and Type B behavior patterns. They theorized that intense, hard-driving Type A personalities had a higher risk of coronary disease because they are "stress junkies." Type B people, on the other hand, tended to be relaxed, less competitive, and lower in risk. There was also a Type AB mixed profile. 

John L. Holland's RIASEC vocational model, commonly referred to as the Holland Codes, stipulates that six personality types lead people to choose their career paths. In this circumplex model, the six types are represented as a hexagon, with adjacent types more closely related than those more distant. The model is widely used in vocational counseling.

Eduard Spranger's personality-model, consisting of six (or, by some revisions, 6 +1) basic types of value attitudes, described in his book Types of Men (Lebensformen; Halle (Saale): Niemeyer, 1914; English translation by P. J. W. Pigors - New York: G. E. Stechert Company, 1928). 

The Enneagram of Personality, a model of human personality which is principally used as a typology of nine interconnected personality types. It has been criticized as being subject to interpretation, making it difficult to test or validate scientifically.

Perhaps the most ancient attempt at personality psychology is the personality typology outlined by the Indian Buddhist Abhidharma schools. This typology mostly focuses on negative personal traits (greed, hatred, and delusion) and the corresponding positive meditation practices used to counter those traits.

Psychoanalytic theories

Psychoanalytic theories explain human behavior in terms of the interaction of various components of personality. Sigmund Freud was the founder of this school of thought. Freud drew on the physics of his day (thermodynamics) to coin the term psychodynamics. Based on the idea of converting heat into mechanical energy, he proposed psychic energy could be converted into behavior. Freud's theory places central importance on dynamic, unconscious psychological conflicts.

Freud divides human personality into three significant components: the id, ego and super-ego. The id acts according to the pleasure principle, demanding immediate gratification of its needs regardless of external environment; the ego then must emerge in order to realistically meet the wishes and demands of the id in accordance with the outside world, adhering to the reality principle. Finally, the superego (conscience) inculcates moral judgment and societal rules upon the ego, thus forcing the demands of the id to be met not only realistically but morally. The superego is the last function of the personality to develop, and is the embodiment of parental/social ideals established during childhood. According to Freud, personality is based on the dynamic interactions of these three components.

The channeling and release of sexual (libidal) and aggressive energies, which ensues from the "Eros" (sex; instinctual self-preservation) and "Thanatos" (death; instinctual self-annihilation) drives respectively, are major components of his theory. It is important to note that Freud's broad understanding of sexuality included all kinds of pleasurable feelings experienced by the human body.

Freud proposed five psychosexual stages of personality development. He believed adult personality is dependent upon early childhood experiences and largely determined by age five. Fixations that develop during the infantile stage contribute to adult personality and behavior.

One of Sigmund Freud's earlier associates, Alfred Adler, did agree with Freud that early childhood experiences are important to development and believed birth order may influence personality development. Adler believed that the oldest child was the individual who would set high achievement goals in order to gain attention lost when the younger siblings were born. He believed the middle children were competitive and ambitious. He reasoned that this behavior was motivated by the idea of surpassing the firstborn's achievements. He added, however, that the middle children were often not as concerned about the glory attributed with their behavior. He also believed the youngest would be more dependent and sociable. Adler finished by surmising that an only child loves being the center of attention and matures quickly but in the end fails to become independent.

Heinz Kohut thought similarly to Freud's idea of transference. He used narcissism as a model of how people develop their sense of self. Narcissism is the exaggerated sense of one self in which one is believed to exist in order to protect one's low self-esteem and sense of worthlessness. Kohut had a significant impact on the field by extending Freud's theory of narcissism and introducing what he called the 'self-object transferences' of mirroring and idealization. In other words, children need to idealize and emotionally "sink into" and identify with the idealized competence of admired figures such as parents or older siblings. They also need to have their self-worth mirrored by these people. These experiences allow them to thereby learn the self-soothing and other skills that are necessary for the development of a healthy sense of self.

Another important figure in the world of personality theory is Karen Horney. She is credited with the development of the "real self" and the "ideal self". She believes all people have these two views of their own self. The "real self" is how humans act with regard to personality, values, and morals; but the "ideal self" is a construct individuals implement in order to conform to social and personal norms.

Behaviorist theories

Behaviorists explain personality in terms of the effects external stimuli have on behavior. The approaches used to analyze the behavioral aspect of personality are known as behavioral theories or learning-conditioning theories. These approaches were a radical shift away from Freudian philosophy. One of the major tenets of this concentration of personality psychology is a strong emphasis on scientific thinking and experimentation. This school of thought was developed by B. F. Skinner who put forth a model which emphasized the mutual interaction of the person or "the organism" with its environment. Skinner believed children do bad things because the behavior obtains attention that serves as a reinforcer. For example: a child cries because the child's crying in the past has led to attention. These are the response, and consequences. The response is the child crying, and the attention that child gets is the reinforcing consequence. According to this theory, people's behavior is formed by processes such as operant conditioning. Skinner put forward a "three term contingency model" which helped promote analysis of behavior based on the "Stimulus - Response - Consequence Model" in which the critical question is: "Under which circumstances or antecedent 'stimuli' does the organism engage in a particular behavior or 'response', which in turn produces a particular 'consequence'?"

Richard Herrnstein extended this theory by accounting for attitudes and traits. An attitude develops as the response strength (the tendency to respond) in the presences of a group of stimuli become stable. Rather than describing conditionable traits in non-behavioral language, response strength in a given situation accounts for the environmental portion. Herrstein also saw traits as having a large genetic or biological component, as do most modern behaviorists.

Ivan Pavlov is another notable influence. He is well known for his classical conditioning experiments involving dogs, which led him to discover the foundation of behaviorism.

Social cognitive theories

In cognitive theory, behavior is explained as guided by cognitions (e.g. expectations) about the world, especially those about other people. Cognitive theories are theories of personality that emphasize cognitive processes, such as thinking and judging.

Albert Bandura, a social learning theorist suggested the forces of memory and emotions worked in conjunction with environmental influences. Bandura was known mostly for his "Bobo doll experiment". During these experiments, Bandura video taped a college student kicking and verbally abusing a bobo doll. He then showed this video to a class of kindergarten children who were getting ready to go out to play. When they entered the play room, they saw bobo dolls, and some hammers. The people observing these children at play saw a group of children beating the doll. He called this study and his findings observational learning, or modeling.

Early examples of approaches to cognitive style are listed by Baron (1982). These include Witkin's (1965) work on field dependency, Gardner's (1953) discovering people had consistent preference for the number of categories they used to categorise heterogeneous objects, and Block and Petersen's (1955) work on confidence in line discrimination judgments. Baron relates early development of cognitive approaches of personality to ego psychology. More central to this field have been:

• Attributional style theory dealing with different ways in which people explain events in their lives. This approach builds upon locus of control, but extends it by stating we also need to consider whether people attribute to stable causes or variable causes, and to global causes or specific causes.

Various scales have been developed to assess both attributional style and locus of control. Locus of control scales include those used by Rotter and later by Duttweiler, the Nowicki and Strickland (1973) Locus of Control Scale for Children and various locus of control scales specifically in the health domain, most famously that of Kenneth Wallston and his colleagues, The Multidimensional Health Locus of Control Scale. Attributional style has been assessed by the Attributional Style Questionnaire, the Expanded Attributional Style Questionnaire, the Attributions Questionnaire, the Real Events Attributional Style Questionnaire, and the Attributional Style Assessment Test.

• Achievement style theory focuses upon identification of an individual's Locus of Control tendency, such as by Rotter's evaluations, and was found by Cassandra Bolyard Whyte to provide valuable information for improving academic performance of students. Individuals with internal control tendencies are likely to persist to better academic performance levels, presenting an achievement personality, according to Cassandra B. Whyte.

Recognition that the tendency to believe that hard work and persistence often results in attainment of life and academic goals has influenced formal educational and counseling efforts with students of various ages and in various settings since the 1970s research about achievement. Counseling aimed toward encouraging individuals to design ambitious goals and work toward them, with recognition that there are external factors that may impact, often results in the incorporation of a more positive achievement style by students and employees, whatever the setting, to include higher education, workplace, or justice programming.

Walter Mischel (1999) has also defended a cognitive approach to personality. His work refers to "Cognitive Affective Units", and considers factors such as encoding of stimuli, affect, goal-setting, and self-regulatory beliefs. The term "Cognitive Affective Units" shows how his approach considers affect as well as cognition.

Cognitive-Experiential Self-Theory (CEST) is another cognitive personality theory. Developed by Seymour Epstein, CEST argues that humans operate by way of two independent information processing systems: experiential system and rational system. The experiential system is fast and emotion-driven. The rational system is slow and logic-driven. These two systems interact to determine our goals, thoughts, and behavior.

Personal construct psychology (PCP) is a theory of personality developed by the American psychologist George Kelly in the 1950s. Kelly's fundamental view of personality was that people are like naive scientists who see the world through a particular lens, based on their uniquely organized systems of construction, which they use to anticipate events. But because people are naive scientists, they sometimes employ systems for construing the world that are distorted by idiosyncratic experiences not applicable to their current social situation. A system of construction that chronically fails to characterize and/or predict events, and is not appropriately revised to comprehend and predict one's changing social world, is considered to underlie psychopathology (or mental illness.) From the theory, Kelly derived a psychotherapy approach and also a technique called The Repertory Grid Interview that helped his patients to uncover their own "constructs" with minimal intervention or interpretation by the therapist. The repertory grid was later adapted for various uses within organizations, including decision-making and interpretation of other people's world-views.

Humanistic theories

Humanistic psychology emphasizes that people have free will and that this plays an active role in determining how they behave. Accordingly, humanistic psychology focuses on subjective experiences of persons as opposed to forced, definitive factors that determine behavior. Abraham Maslow and Carl Rogers were proponents of this view, which is based on the "phenomenal field" theory of Combs and Snygg (1949). Rogers and Maslow were among a group of psychologists that worked together for a decade to produce the Journal of Humanistic Psychology. This journal was primarily focused on viewing individuals as a whole, rather than focusing solely on separate traits and processes within the individual.

Robert W. White wrote the book The Abnormal Personality that became a standard text on abnormal psychology. He also investigated the human need to strive for positive goals like competence and influence, to counterbalance the emphasis of Freud on the pathological elements of personality development.

Maslow spent much of his time studying what he called "self-actualizing persons", those who are "fulfilling themselves and doing the best they are capable of doing". Maslow believes all who are interested in growth move towards self-actualizing (growth, happiness, satisfaction) views. Many of these people demonstrate a trend in dimensions of their personalities. Characteristics of self-actualizers according to Maslow include the four key dimensions:

1. Awareness – maintaining constant enjoyment and awe of life. These individuals often experienced a "peak experience". He defined a peak experience as an "intensification of any experience to the degree there is a loss or transcendence of self". A peak experience is one in which an individual perceives an expansion of themselves, and detects a unity and meaningfulness in life. Intense concentration on an activity one is involved in, such as running a marathon, may invoke a peak experience.
2. Reality and problem centered – having a tendency to be concerned with "problems" in surroundings.
3. Acceptance/Spontaneity – accepting surroundings and what cannot be changed.
4. Unhostile sense of humor/democratic – do not take kindly to joking about others, which can be viewed as offensive. They have friends of all backgrounds and religions and hold very close friendships.

Maslow and Rogers emphasized a view of the person as an active, creative, experiencing human being who lives in the present and subjectively responds to current perceptions, relationships, and encounters. They disagree with the dark, pessimistic outlook of those in the Freudian psychoanalysis ranks, but rather view humanistic theories as positive and optimistic proposals which stress the tendency of the human personality toward growth and self-actualization. This progressing self will remain the center of its constantly changing world; a world that will help mold the self but not necessarily confine it. Rather, the self has opportunity for maturation based on its encounters with this world. This understanding attempts to reduce the acceptance of hopeless redundancy. Humanistic therapy typically relies on the client for information of the past and its effect on the present, therefore the client dictates the type of guidance the therapist may initiate. This allows for an individualized approach to therapy. Rogers found patients differ in how they respond to other people. Rogers tried to model a particular approach to therapy- he stressed the reflective or empathetic response. This response type takes the client's viewpoint and reflects back their feeling and the context for it. An example of a reflective response would be, "It seems you are feeling anxious about your upcoming marriage". This response type seeks to clarify the therapist's understanding while also encouraging the client to think more deeply and seek to fully understand the feelings they have expressed.

Biopsychological theories

False-color representations of cere­bral fiber path­ways affect­ed in Phineas Gage's accident, per Van Horn et al.

 

Biology plays a very important role in the development of personality. The study of the biological level in personality psychology focuses primarily on identifying the role of genetic determinants and how they mold individual personalities. Some of the earliest thinking about possible biological bases of personality grew out of the case of Phineas Gage. In an 1848 accident, a large iron rod was driven through Gage's head, and his personality apparently changed as a result, although descriptions of these psychological changes are usually exaggerated.

In general, patients with brain damage have been difficult to find and study. In the 1990s, researchers began to use electroencephalography (EEG), positron emission tomography (PET), and more recently functional magnetic resonance imaging (fMRI), which is now the most widely used imaging technique to help localize personality traits in the brain.

Genetic basis of personality

Ever since the Human Genome Project allowed for a much more in depth understanding of genetics, there has been an ongoing controversy involving heritability, personality traits, and environmental vs. genetic influence on personality. The human genome is known to play a role in the development of personality.

Previously, genetic personality studies focused on specific genes correlating to specific personality traits. Today's view of the gene-personality relationship focuses primarily on the activation and expression of genes related to personality and forms part of what is referred to as behavioural genetics. Genes provide numerous options for varying cells to be expressed; however, the environment determines which of these are activated. Many studies have noted this relationship in varying ways in which our bodies can develop, but the interaction between genes and the shaping of our minds and personality is also relevant to this biological relationship.

DNA-environment interactions are important in the development of personality because this relationship determines what part of the DNA code is actually made into proteins that will become part of an individual. While different choices are made available by the genome, in the end, the environment is the ultimate determinant of what becomes activated. Small changes in DNA in individuals are what lead to the uniqueness of every person as well as differences in looks, abilities, brain functioning, and all the factors that culminate to develop a cohesive personality.

Cattell and Eysenck have proposed that genetics have a strong influence on personality. A large part of the evidence collected linking genetics and the environment to personality have come from twin studies. This "twin method" compares levels of similarity in personality using genetically identical twins. One of the first of these twin studies measured 800 pairs of twins, studied numerous personality traits, and determined that identical twins are most similar in their general abilities. Personality similarities were found to be less related for self-concepts, goals, and interests.

Twin studies have also been important in the creation of the five factor personality model: neuroticism, extraversion, openness, agreeableness, and conscientiousness. Neuroticism and extraversion are the two most widely studied traits. A person that may fall into the extravert category can display characteristics such as impulsiveness, sociability, and activeness. A person falling into the neuroticism category may be more likely to be moody, anxious, or irritable. Identical twins, however, have higher correlations in personality traits than fraternal twins. One study measuring genetic influence on twins in five different countries found that the correlations for identical twins were .50, while for fraternal they were about .20. It is suggested that heredity and environment interact to determine one's personality.

Evolutionary theory

Charles Darwin is the founder of the theory of the evolution of the species. The evolutionary approach to personality psychology is based on this theory. This theory examines how individual personality differences are based on natural selection. Through natural selection organisms change over time through adaptation and selection. Traits are developed and certain genes come into expression based on an organism's environment and how these traits aid in an organism's survival and reproduction. 

Polymorphisms, such as gender and blood type, are forms of diversity which evolve to benefit a species as a whole. The theory of evolution has wide-ranging implications on personality psychology. Personality viewed through the lens of evolutionary psychology places a great deal of emphasis on specific traits that are most likely to aid in survival and reproduction, such as conscientiousness, sociability, emotional stability, and dominance. The social aspects of personality can be seen through an evolutionary perspective. Specific character traits develop and are selected for because they play an important and complex role in the social hierarchy of organisms. Such characteristics of this social hierarchy include the sharing of important resources, family and mating interactions, and the harm or help organisms can bestow upon one another.

Drive theories

In the 1930s, John Dollard and Neal Elgar Miller met at Yale University, and began an attempt to integrate drives, into a theory of personality, basing themselves on the work of Clark Hull. They began with the premise that personality could be equated with the habitual responses exhibited by an individual – their habits. From there, they determined that these habitual responses were built on secondary, or acquired drives.

Secondary drives are internal needs directing the behaviour of an individual that results from learning. Acquired drives are learned, by and large in the manner described by classical conditioning. When we are in a certain environment and experience a strong response to a stimulus, we internalize cues from the said environment. When we find ourselves in an environment with similar cues, we begin to act in anticipation of a similar stimulus. Thus, we are likely to experience anxiety in an environment with cues similar to one where we have experienced pain or fear – such as the dentist's office.

Secondary drives are built on primary drives, which are biologically driven, and motivate us to act with no prior learning process – such as hunger, thirst or the need for sexual activity. However, secondary drives are thought to represent more specific elaborations of primary drives, behind which the functions of the original primary drive continue to exist. Thus, the primary drives of fear and pain exist behind the acquired drive of anxiety. Secondary drives can be based on multiple primary drives and even in other secondary drives. This is said to give them strength and persistence. Examples include the need for money, which was conceptualized as arising from multiple primary drives such as the drive for food and warmth, as well as from secondary drives such as imitativeness (the drive to do as others do) and anxiety.

Secondary drives vary based on the social conditions under which they were learned – such as culture. Dollard and Miller used the example of food, stating that the primary drive of hunger manifested itself behind the learned secondary drive of an appetite for a specific type of food, which was dependent on the culture of the individual.

Secondary drives are also explicitly social, representing a manner in which we convey our primary drives to others. Indeed, many primary drives are actively repressed by society (such as the sexual drive). Dollard and Miller believed that the acquisition of secondary drives was essential to childhood development. As children develop, they learn not to act on their primary drives, such as hunger but acquire secondary drives through reinforcement. Friedman and Schustack describe an example of such developmental changes, stating that if an infant engaging in an active orientation towards others brings about the fulfillment of primary drives, such as being fed or having their diaper changed, they will develop a secondary drive to pursue similar interactions with others – perhaps leading to an individual being more gregarious. Dollard and Miller's belief in the importance of acquired drives led them to reconceive Sigmund Freud's theory of psychosexual development. They found themselves to be in agreement with the timing Freud used but believed that these periods corresponded to the successful learning of certain secondary drives.

Dollard and Miller gave many examples of how secondary drives impact our habitual responses – and by extension our personalities, including anger, social conformity, imitativeness or anxiety, to name a few. In the case of anxiety, Dollard and Miller note that people who generalize the situation in which they experience the anxiety drive will experience anxiety far more than they should. These people are often anxious all the time, and anxiety becomes part of their personality. This example shows how drive theory can have ties with other theories of personality – many of them look at the trait of neuroticism or emotional stability in people, which is strongly linked to anxiety.

Personality tests

There are two major types of personality tests, projective and objective. 

Projective tests assume personality is primarily unconscious and assess individuals by how they respond to an ambiguous stimulus, such as an ink blot. Projective tests have been in use for about 60 years and continue to be used today. Examples of such tests include the Rorschach test and the Thematic Apperception Test. 

The Rorschach Test involves showing an individual a series of note cards with ambiguous ink blots on them. The individual being tested is asked to provide interpretations of the blots on the cards by stating everything that the ink blot may resemble based on their personal interpretation. The therapist then analyzes their responses. Rules for scoring the test have been covered in manuals that cover a wide variety of characteristics such as content, originality of response, location of "perceived images" and several other factors. Using these specific scoring methods, the therapist will then attempt to relate test responses to attributes of the individual's personality and their unique characteristics. The idea is that unconscious needs will come out in the person's response, e.g. an aggressive person may see images of destruction.

The Thematic Apperception Test (also known as the TAT) involves presenting individuals with vague pictures/scenes and asking them to tell a story based on what they see. Common examples of these "scenes" include images that may suggest family relationships or specific situations, such as a father and son or a man and a woman in a bedroom. Responses are analyzed for common themes. Responses unique to an individual are theoretically meant to indicate underlying thoughts, processes, and potentially conflicts present within the individual. Responses are believed to be directly linked to unconscious motives. There is very little empirical evidence available to support these methods.

Objective tests assume personality is consciously accessible and that it can be measured by self-report questionnaires. Research on psychological assessment has generally found objective tests to be more valid and reliable than projective tests. Critics have pointed to the Forer effect to suggest some of these appear to be more accurate and discriminating than they really are. Issues with these tests include false reporting because there is no way to tell if an individual is answering a question honestly or accurately.

The Myers-Briggs Type Indicator (also known as the MBTI) is self-reporting questionnaire based on Carl Jung's Type theory.

Personality theory assessment criteria

• Verifiability - the theory should be formulated in such a way that the concepts, suggestions and hypotheses involved in it are defined clearly and unambiguously, and logically related to each other.
• Heuristic value - to what extent the theory stimulates scientists to conduct further research.
• Internal consistency - the theory should be free from internal contradictions.
• Economy - the fewer concepts and assumptions required by the theory to explain any phenomenon, the better it is Hjelle, Larry (1992). Personality Theories: Basic Assumptions, Research, and Applications.

Psychology has traditionally defined personality through its behavioral patterns, and more recently with neuroscientific studies of the brain. In recent years, some psychologists have turned to the study of inner experiences for insight into personality as well as individuality. Inner experiences are the thoughts and feelings to an immediate phenomenon. Another term used to define inner experiences is qualia. Being able to understand inner experiences assists in understanding how humans behave, act, and respond. Defining personality using inner experiences has been expanding due to the fact that solely relying on behavioral principles to explain one's character may seem incomplete. Behavioral methods allow the subject to be observed by an observer, whereas with inner experiences the subject is its own observer.

Methods measuring inner experience

Descriptive experience sampling (DES), developed by psychologist Russel Hurlburt. This is an idiographic method that is used to help examine inner experiences. This method relies on an introspective technique that allows an individual's inner experiences and characteristics to be described and measured. A beep notifies the subject to record their experience at that exact moment and 24 hours later an interview is given based on all the experiences recorded. DES has been used in subjects that have been diagnosed with schizophrenia and depression. It has also been crucial to studying the inner experiences of those who have been diagnosed with common psychiatric diseases.

Articulated thoughts in stimulated situations (ATSS): ATSS is a paradigm which was created as an alternative to the TA (think aloud) method. This method assumes that people have continuous internal dialogues that can be naturally attended to. ATSS also assesses a person’s inner thoughts as they verbalize their cognitions. In this procedure, subjects listen to a scenario via a video or audio player and are asked to imagine that they are in that specific situation. Later, they are asked to articulate their thoughts as they occur in reaction to the playing scenario. This method is useful in studying emotional experience given that the scenarios used can influence specific emotions. Most importantly, the method has contributed to the study of personality. In a study conducted by Rayburn and Davison (2002), subjects’ thoughts and empathy toward anti-gay hate crimes were evaluated. The researchers found that participants showed more aggressive intentions towards the offender in scenarios which mimicked hate crimes.

Experimental method: This method is an experimental paradigm used to study human experiences involved in the studies of sensation and perception, learning and memory, motivation, and biological psychology. The experimental psychologist usually deals with intact organisms although studies are often conducted with organisms modified by surgery, radiation, drug treatment, or long-standing deprivations of various kinds or with organisms that naturally present organic abnormalities or emotional disorders. Economists and psychologists have developed a variety of experimental methodologies to elicit and assess individual attitudes where each emotion differs for each individual. The results are then gathered and quantified to conclude if specific experiences have any common factors. This method is used to seek clarity of the experience and remove any biases to help understand the meaning behind the experience to see if it can be generalized.