Primatology

From Wikipedia, the free encyclopedia

 

Olive baboon

 

Primatology is the scientific study of primates. It is a diverse discipline at the boundary between mammalogy and anthropology, and researchers can be found in academic departments of anatomy, anthropology, biology, medicine, psychology, veterinary sciences and zoology, as well as in animal sanctuaries, biomedical research facilities, museums and zoos. Primatologists study both living and extinct primates in their natural habitats and in laboratories by conducting field studies and experiments in order to understand aspects of their evolution and behaviour.

Sub-disciplines

As a science, primatology has many different sub-disciplines which vary in terms of theoretical and methodological approaches to the subject used in researching extant primates and their extinct ancestors. 

There are two main centers of primatology, Western primatology and Japanese primatology. These two divergent disciplines stem from their unique cultural backgrounds and philosophies that went into their founding. Although, fundamentally, both Western and Japanese primatology share many of the same principles, the areas of their focus in primate research and their methods of obtaining data differ widely.

Western primatology

Origins

Western primatology stems primarily from research by North American and European scientists. Early primate study focused primarily in medical research, but some scientists also conducted "civilizing" experiments on chimpanzees in order to gauge both primate intelligence and the limits of their brainpower.

Theory

The study of primatology looks at the biological and psychological aspects of non-human primates. The focus is on studying the common links between humans and primates. It is believed that by understanding our closest animal relatives, we might better understand the nature shared with our ancestors.

Methods

Primatology is a science. The general belief is that the scientific observation of nature must be either extremely limited, or completely controlled. Either way, the observers must be neutral to their subjects. This allows for data to be unbiased and for the subjects to be uninfluenced by human interference. 

There are three methodological approaches in primatology: field study, the more realistic approach, laboratory study, the more controlled approach, and semi-free ranging, where primate habitat and wild social structure is replicated in a captive setting. 

Field is done in natural environments, in which scientific observers watch primates in their natural habitat. 

Laboratory study is done in controlled lab settings. In lab settings, scientists are able to perform controlled experimentation on the learning capabilities and behavioral patterns of the animals. 

In semi-free ranging studies, scientists are able to watch how primates might act in the wild but have easier access to them, and the ability to control their environments. Such facilities include the Living Links Center at the Yerkes National Primate Research Center in Georgia and the Elgin Center at Lion Country Safari in Florida. 

All types of primate study in the Western methodology are meant to be neutral. Although there are certain Western primatologists who do more subjective research, the emphasis in this discipline is on the objective. 

Early field primatology tended to focus on individual researchers. Researchers such as Dian Fossey and Jane Goodall and Birute Galdikas are examples of this. In 1960, Jane Goodall traveled to the forest at Gombe Stream in Tanzania where her determination and skill allowed for her to observe behaviors of the chimpanzees that no researcher had seen prior. Chimpanzees used tools made from twigs to extract termites from their nests. Additionally, Dian Fossey’s work conducted at the Karisoke Research station in Rwanda proved the possibility of habituation among the mountain gorillas. Fossey learned that female gorillas are often transferred between groups and gorillas eat their own dung to recycle nutrients. The third “trimate”, Birute Galdikas spent over 12 years becoming habituated to the orangutans in Borneo, Indonesia. Galdikas utilized statistics and modern data collection to conclude her 1978 doctoral thesis regarding orangutan behavior and interactions. Long-term sites of research tend to be best associated with their founders, and this led to some tension between younger primatologists and the veterans in the field.

Notable Western primatologists

• Jeanne Altmann
• Sarah Blaffer Hrdy
• Christophe Boesch
• Geoffrey Bourne
• Josep Call
• C. R. Carpenter
• Colin Chapman
• Dorothy_Cheney_(scientist)
• Frans de Waal
• Thomas Defler
• Alejandro Estrada
• Linda Fedigan
• Dian Fossey
• Agustin Fuentes
• Birutė Galdikas
• Paul Garber
• Richard Lynch Garner
• Jane Goodall
• Colin Groves
• Harry Harlow
• Philip Hershkovitz
• Alison Jolly
• Nadezhda Ladygina-Kohts
• Louis Leakey
• Robert D. Martin
• Emil Wolfgang Menzel, Jr.
• Russell Mittermeier
• John R. Napier
• Carlos A. Peres
• Matthew Richardson
• Anne E. Russon
• Jordi Sabater Pi
• Robert Sapolsky
• Carel van Schaik
• Robert_Seyfarth_(scientist)
• Meredith Small
• Barbara Smuts
• Craig Stanford
• Robert W. Sussman
• Michael Tomasello
• Omar Wasow
• Sherwood Washburn
• David P. Watts
• Richard Wrangham

Japanese primatology

Origins

The discipline of Japanese primatology was developed out of animal ecology. It is mainly credited to Kinji Imanishi and Junichiro Itani. Imanishi was an animal ecologist who began studying wild horses before focusing more on primate ecology. He helped found the Primate Research Group in 1950. Junichiro was a renowned anthropologist and a professor at Kyoto University. He is a co-founder of the Primate Research Institute and the Centre for African Area Studies.

Theory

The Japanese discipline of primatology tends to be more interested in the social aspects of primates. Social evolution and anthropology are of primary interest to them. The Japanese theory believes that studying primates will give us insight into the duality of human nature: individual self vs. social self.

The traditional and cultural aspects of Japanese science lend themselves to an “older sibling” mentality. It is believed that animals should be treated with respect, but also a firm authority. This is not to say that the Japanese study of primatology is cruel – far from it – just that it does not feel that their subjects should be given reverential treatment. 

One particular Japanese primatologist, Kawai Masao, introduced the concept of kyokan. This was the theory that the only way to attain reliable scientific knowledge was to attain a mutual relation, personal attachment and shared life with the animal subjects. Though Kawai is the only Japanese primatologist associated with the use of this term, the underlying principle is part of the foundation of Japanese primate research.

Methods

Japanese primatology is a carefully disciplined subjective science. It is believed that the best data comes through identification with your subject. Neutrality is eschewed in favour of a more casual atmosphere, where researcher and subject can mingle more freely. Domestication of nature is not only desirable, but necessary for study. 

Japanese primatologists are renowned for their ability to recognise animals by sight, and indeed most primates in a research group are usually named and numbered. Comprehensive data on every single subject in a group is uniquely Japanese trait of primate research. Each member of the primate community has a part to play, and the Japanese researchers are interested in this complex interaction.

For Japanese researchers in primatology, the findings of the team are emphasised over the individual. The study of primates is a group effort, and the group will get the credit for it. A team of researchers may observe a group of primates for several years in order to gather very detailed demographic and social histories.

Notable Japanese primatologists

• Kinji Imanishi
• Junichiro Itani
• Kawai Masao
• Tetsuro Matsuzawa
• Toshisada Nishida
• Satsue Mito

Primatology in sociobiology

Where sociobiology attempts to understand the actions of all animal species within the context of advantageous and disadvantageous behaviors, primatology takes an exclusive look at the order Primates, which includes Homo sapiens. The interface between primatology and sociobiology examines in detail the evolution of primate behavioral processes, and what studying our closest living primate relatives can tell about our own minds. As the American anthropologist Earnest Albert Hooton used to say, "Primas sum: primatum nil a me alienum puto." ("I am a primate; nothing about primates is outside of my bailiwick".) The meeting point of these two disciplines has become a nexus of discussion on key issues concerning the evolution of sociality, the development and purpose of language and deceit, and the development and propagation of culture. 

Additionally, this interface is of particular interest to the science watchers in science and technology studies, who examine the social conditions which incite, mould, and eventually react to scientific discoveries and knowledge. The STS approach to primatology and sociobiology stretches beyond studying the apes, into the realm of observing the people studying the apes.

Taxonomic basis

Before Darwin, and before molecular biology, the father of modern taxonomy, Carl Linnaeus, organized natural objects into kinds, that we now know reflect their evolutionary relatedness. He sorted these kinds by morphology, the shape of the object. Animals such as monkeys, chimpanzees and orangutans resemble humans closely, so Linnaeus placed Homo sapiens together with other similar-looking organisms into the taxonomic order Primates. Modern molecular biology reinforced humanity’s place within the Primate order. Humans and simians share the vast majority of their DNA, with chimpanzees sharing between 97-99% genetic identity with humans.

From grooming to speaking

Although social grooming is observed in many animal species, the grooming activities undertaken by primates are not strictly for the elimination of parasites. In primates, grooming is a social activity that strengthens relationships. The amount of grooming taking place between members of a troop is a potent indicator of alliance formation or troop solidarity. Robin Dunbar suggests a link between primate grooming and the development of human language. The size of the neocortex in a primate’s brain correlates directly to the number of individuals it can keep track of socially, be it a troop of chimps or a tribe of humans.

This number is referred to as the monkeysphere. If a population exceeds the size outlined by its cognitive limitations, the group undergoes a schism. Set into an evolutionary context, the Dunbar number shows a drive for the development of a method of bonding that is less labor-intensive than grooming: language. As the monkeysphere grows, the amount of time that would need to be spent grooming troopmates soon becomes unmanageable. Furthermore, it is only possible to bond with one troopmate at a time while grooming. The evolution of vocal communication solves both the time constraint and the one-on-one problem, but at a price. 

Language allows for bonding with multiple people at the same time at a distance, but the bonding produced by language is less intense. This view of language evolution covers the general biological trends needed for language development, but it takes another hypothesis to uncover the evolution of the cognitive processes necessary for language.

Modularity of the primate mind

Noam Chomsky’s concept of innate language addresses the existence of universal grammar, which suggests a special kind of “device” all humans are born with whose sole purpose is language. Fodor’s modular mind hypothesis expands on this concept, suggesting the existence of preprogrammed modules for dealing with many, or all aspects of cognition. Although these modules do not need to be physically distinct, they must be functionally distinct. Orangutans are currently being taught language at the Smithsonian National Zoo using a computer system developed by primatologist Dr. Francine Neago in conjunction with IBM.

The massive modularity theory thesis posits that there is a huge number of tremendously interlinked but specialized modules running programs called Darwinian algorithms, or DA. DA can be selected for just as a gene can, eventually improving cognition. The contrary theory, of generalist mind, suggests that the brain is just a big computer that runs one program, the mind. If the mind is a general computer, for instance, the ability to use reasoning should be identical regardless of the context. This is not what is observed. When faced with abstract numbers and letters with no “real world” significance, respondents of the Wason card test generally do very poorly. However, when exposed to a test with an identical rule set but socially relevant content, respondents score markedly higher. The difference is especially pronounced when the content is about reward and payment. This test strongly suggests that human logic is based on a module originally developed in a social environment to root out cheaters, and that either the module is at a huge disadvantage where abstract thinking is involved, or that other less effective modules are used when faced with abstract logic.

Further evidence supporting the modular mind has steadily emerged with some startling revelations concerning primates. A very recent study indicated that human babies and grown monkeys approach and process numbers in a similar fashion, suggesting an evolved set of DA for mathematics (Jordan). The conceptualization of both human infants and primate adults is cross-sensory, meaning that they can add 15 red dots to 20 beeps and approximate the answer to be 35 grey squares. As more evidence of basic cognitive modules are uncovered, they will undoubtedly form a more solid foundation upon which the more complex behaviors can be understood. 

In contradiction to this, neuroscientist Jaak Panksepp has argued that the mind is not a computer nor is it massively modular. He states that no evidence of massive modularity or the brain as a digital computer has been gained through actual neuroscience, as opposed to psychological studies. He criticises psychologists who use the massive modularity thesis for not integrating neuroscience into their understanding.

The primate theory of mind

Primate behavior, like human behavior, is highly social and ripe with the intrigue of kingmaking, powerplays, deception, cuckoldry, and apology. In order to understand the staggeringly complex nature of primate interactions, we look to theory of mind. Theory of mind asks whether or not an individual recognizes and can keep track of information asymmetry amongst individuals in the group, and whether or not they can attribute folk psychological states to their peers. If some primates can tell what others know and want and act accordingly, they can gain advantage and status. 

Recently, chimpanzee theory of mind has been advanced by Felix Warneken of the Max Planck Institute. His studies have shown that chimpanzees can recognize whether a researcher desires a dropped object, and act accordingly by picking it up. Even more compelling is the observation that chimps will only act if the object is dropped in an accidental-looking manner: if the researcher drops the object in a way that appears intentional, the chimp will ignore the object. 

In a related experiment, groups of chimps were given rope-pulling problems they could not solve individually. Warneken’s subjects rapidly figured out which individual in the group was the best rope puller and assigned it the bulk of the task. This research is highly indicative of the ability of chimps to detect the folk psychological state of “desire”, as well as the ability to recognize that other individuals are better at certain tasks than they are. 

However primates do not always fare so well in situations requiring theory of mind. In one experiment pairs of chimpanzees who had been close grooming partners were offered two levers. Pressing one lever would bring them food and another would bring their grooming partner food. Pressing the lever to clearly give their grooming partner much-wanted food would not take away from how much food they themselves got. For some reason, the chimps were unwilling to depress the lever that would give their long-time chums food. It is plausible but unlikely that the chimps figured there was finite food and it would eventually decrease their own food reward. The experiments are open to such interpretations making it hard to establish anything for certain. 

One phenomenon which would indicate a possible fragility of theory of mind in primates occurs when a baboon gets lost. Under such circumstances, the lost baboon generally makes "call barks" to announce that it is lost. Previous to the 1990s it was thought that these call barks would then be returned by the other baboons, similar to the case is in vervet monkeys. However, when researchers studied this formally in the past few years they found something surprising: Only the baboons who were lost would ever give call barks. Even if an infant was wailing in agony just a few hundred meters away, its mother who would clearly recognise its voice and would be frantic about his safety (or alternatively run towards her infant depending on her own perceived safety), would often simply stare in his direction visibly agitated. If the anguishing baboon mother made any type of call at all, the infant would instantly recognise her and run to her position. This type of logic appears to be lost on the baboon, suggesting a serious gap in theory of mind of this otherwise seemingly very intelligent primate species. However, it is also possible that baboons do not return call barks for ecological reasons, for example because returning the call bark might call attention to the lost baboon, putting it at greater risk from predators.

Criticisms

Scientific studies concerning primate and human behavior have been subject to the same set of political and social complications, or biases, as every other scientific discipline. The borderline and multidisciplinary nature of primatology and sociobiology make them ripe fields of study because they are amalgams of objective and subjective sciences. Current scientific practice, especially in the hard sciences, requires a total dissociation of personal experience from the finished scientific product (Bauchspies 8). This is a strategy that is incompatible with observational field studies, and weakens them in the eyes of hard science. As mentioned above, the Western school of primatology tries to minimize subjectivity, while the Japanese school of primatology tends to embrace the closeness inherent in studying nature. 

Social critics of science, some operating from within the field, are critical of primatology and sociobiology. Claims are made that researchers bring pre-existing opinions on issues concerning human sociality to their studies, and then seek evidence that agrees with their worldview or otherwise furthers a sociopolitical agenda. In particular, the use of primatological studies to assert gender roles, and to both promote and subvert feminism has been a point of contention. 

Several research papers on primate cognition were retracted in 2010. Their lead author, primatologist Marc Hauser, was dismissed from Harvard University after an internal investigation found evidence of scientific misconduct in his laboratory. Data supporting the authors' conclusion that cottontop tamarin monkeys displayed pattern-learning behavior similar to human infants reportedly could not be located after a three-year investigation.

Women in primatology

Women receive the majority of Ph.Ds in primatology. Londa Schiebinger, writing in 2001, estimated that women made up 80 percent of graduate students pursuing Ph.Ds in primatology, up from 50 percent in the 1970s. Because of the high number of women, Schiebinger has even asserted that “Primatology is widely celebrated as a feminist science”.

Changing stereotypes

With attention to Darwin’s perception about sexual selection, it was perceived that sexual selection acted differently on females and males. Early research emphasized male-male competition for females. It is widely believed that males tend to woo females, and that females were passive. For years this was the dominant interpretation, emphasizing competition among dominant males who controlled territorial boundaries and maintained order among lesser males. Females on the other hand were described as "dedicated mothers to small infants and sexually available to males in order of the males' dominance rank". Female-female competition was ignored. Schiebinger proposed that the failure to acknowledge female-female competitions could “skew notions of sexual selection" to "ignore interactions between males and females that go beyond the strict interpretation of sex as for reproduction only". In the 1960s primatologists started looking at what females did, slowly changing the stereotype of the passive female. We now know that females are active participants, and even leaders, within their groups. For instance, Rowell found that female baboons determine the route for daily foraging. Similarly, Shirley Strum found that male investment in special relationships with females had greater productive payoff in comparison to a male’s rank in a dominance hierarchy (pr. This emerging “female point of view” resulted in a reanalysis of how aggression, reproductive access, and dominance affect primate societies.

Schiebinger has also accused sociobiologists of producing the “corporate primate”, described as “female baboons with briefcases, strategically competitive and aggressive". This contrasts with the notion that only men are competitive and aggressive. Observations have repeatedly demonstrated that female apes and monkeys also form stable dominance hierarchies and alliances with their male counterparts. Females display aggression, exercise sexual choice, and compete for resources, mates and territory, like their male counterparts.

Six features of feminist science that characterize contemporary primatology (Fedigan)

1. Reflexivity: sensitivity to context and cultural bias in scientific work.
2. “The female point of view”
3. Respect for nature and an ethic cooperation with nature
4. Move away from reductionism
5. Promote humanitarian values rather than national interests
6. Diverse community, accessible and egalitarian

Schiebinger suggests that only two out of the six features characteristic of feminism. One of them is the discussion of the politics of participation and the attention placed on females as subjects of research.

The evolution of primatology

In 1970 Jeanne Altmann drew attention to representative sampling methods in which all individuals, not just the dominant and the powerful, were observed for equal periods of time. Prior to 1970, primatologists used “opportunistic sampling,” which only recorded what caught their attention.

Sarah Hrdy, a self-identified feminist, was among the first to apply what became known as sociobiological theory to primates. In her studies, she focuses on the need for females to win from males parental care for their offspring. 

Linda Fedigan views herself as a reporter or translator, working at the intersection between gender studies of science and the mainstream study of primatology. 

While some influential women challenged fundamental paradigms, Schiebinger suggests that science is constituted by numerous factors varying from gender roles and domestic issues that surround race and class to economic relations between researchers from Developed World countries and the Developing World countries in which most nonhuman primates reside.

Academic resources

Societies

• American Society of Primatologists
• European Federation for Primatology
• International Primatological Society

Journals

• American Journal of Primatology
• Folia Primatologica
• International Journal of Primatology
• Journal of Medical Primatology
• Journal of Human Evolution
• Primates

Homo sapiens

From Wikipedia, the free encyclopedia

Homo sapiens Temporal range: 0.35–0 Ma PreЄ Є O S D C P T J K Pg N ↓ Middle Pleistocene–Present
Male and female H s. sapiens (Akha in northern Thailand, 2007 photograph)
Conservation status
Least Concern (IUCN 3.1)
Scientific classification
Kingdom:	Animalia
Phylum:	Chordata
Class:	Mammalia
Order:	Primates
Suborder:	Haplorhini
Infraorder:	Simiiformes
Family:	Hominidae
Subfamily:	Homininae
Tribe:	Hominini
Genus:	Homo
Species:	H. sapiens
Binomial name
Homo sapiens Linnaeus, 1758
Subspecies
H. s. sapiens †H. s. idaltu †H. s. neanderthalensis(?) †H. s. rhodesiensis(?) (others proposed)

Homo sapiens is the only extant human species. The name is Latin for "wise man" and was introduced in 1758 by Carl Linnaeus (who is himself the lectotype for the species).

Extinct species of the genus Homo include Homo erectus, extant during roughly 1.9 to 0.4 million years ago, and a number of other species (by some authors considered subspecies of either H. sapiens or H. erectus). The age of speciation of H. sapiens out of ancestral H. erectus (or an intermediate species such as Homo antecessor) is estimated to have been roughly 350,000 years ago. Sustained archaic admixture is known to have taken place both in Africa and (following the recent Out-Of-Africa expansion) in Eurasia, between about 100,000 and 30,000 years ago.

The term anatomically modern humans (AMH) is used to distinguish H. sapiens having an anatomy consistent with the range of phenotypes seen in contemporary humans from varieties of extinct archaic humans. This is useful especially for times and regions where anatomically modern and archaic humans co-existed, for example, in Paleolithic Europe.

Name and taxonomy

The binomial name Homo sapiens was coined by Linnaeus, 1758. The Latin noun homō (genitive hominis) means "human being", while the participle sapiēns means "discerning, wise, sensible".

The species was initially thought to have emerged from a predecessor within the genus Homo around 300,000 to 200,000 years ago. A problem with the morphological classification of "anatomically modern" was that it would not have included certain extant populations. For this reason, a lineage-based (cladistic) definition of H. sapiens has been suggested, in which H. sapiens would by definition refer to the modern human lineage following the split from the Neanderthal lineage. Such a cladistic definition would extend the age of H. sapiens to over 500,000 years.

Extant human populations have historically been divided into subspecies, but since around the 1980s all extant groups have tended to be subsumed into a single species, H. sapiens, avoiding division into subspecies altogether.

Some sources show Neanderthals (H. neanderthalensis) as a subspecies (H. sapiens neanderthalensis). Similarly, the discovered specimens of the H. rhodesiensis species have been classified by some as a subspecies (H. sapiens rhodesiensis), although it remains more common to treat these last two as separate species within the genus Homo rather than as subspecies within H. sapiens.

The subspecies name H. sapiens sapiens is sometimes used informally instead of "modern humans" or "anatomically modern humans". It has no formal authority associated with it. By the early 2000s, it had become common to use H. s. sapiens for the ancestral population of all contemporary humans, and as such it is equivalent to the binomial H. sapiens in the more restrictive sense (considering H. neanderthalensis a separate species).

Age and speciation process

Schematic representation of the emergence of H. sapiens from earlier species of Homo. The horizontal axis represents geographic location; the vertical axis represents time in millions of years ago (blue areas denote the presence of a certain species of Homo at a given time and place; late survival of robust australopithecines alongside Homo is indicated in purple). Based on Springer (2012), Homo heidelbergensis is shown as diverging into Neanderthals, Denisovans and H. sapiens. With the rapid expansion of H. sapiens after 60 kya, Neanderthals, Denisovans and unspecified archaic African hominins are shown as again subsumed into the H. sapiens lineage.

Derivation from H. erectus

A model of the phylogeny of H. sapiens during the Middle Paleolithic. The horizontal axis represents geographic location; the vertical axis represents time in thousands of years ago. Neanderthals, Denisovans and unspecified archaic African hominins are shown as admixed into the H. sapiens lineage. In addition, prehistoric Archaic Human and Eurasian admixture events in modern African populations are indicated.

 

The speciation of H. sapiens out of archaic human varieties derived from H. erectus is estimated as having taken place over 350,000 years ago, as the Khoisan split from other populations is dated between 260,000 and 350,000 years ago.

An alternative suggestion defines H. sapiens cladistically as including the lineage of modern humans since the split from the lineage of Neanderthals, roughly 500,000 to 800,000 years ago.

The time of divergence between archaic H. sapiens and ancestors of Neanderthals and Denisovans caused by a genetic 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 H. sapiens, as calculated by Rogers et al. (2017).

The derivation of a comparatively homogeneous single species of H. sapiens from more diverse varieties of archaic humans (all of which were descended from the early dispersal of H. erectus some 1.8 million years ago) was debated in terms of two competing models during the 1980s: "recent African origin" postulated the emergence of H. sapiens from a single source population in Africa, which expanded and led to the extinction of all other human varieties, while the "multiregional evolution" model postulated the survival of regional forms of archaic humans, gradually converging into the modern human varieties by the mechanism of clinal variation, via genetic drift, gene flow and selection throughout the Pleistocene.

Since the 2000s, the availability of data from archaeogenetics and population genetics has led to the emergence of a much more detailed picture, intermediate between the two competing scenarios outlined above: The recent Out-of-Africa expansion accounts for the predominant part of modern human ancestry, while there were also significant admixture events with regional archaic humans.

Since the 1970s, the Omo remains, dated to some 195,000 years ago, have often been taken as the conventional cut-off point for the emergence of "anatomically modern humans". Since the 2000s, the discovery of older remains with comparable characteristics, and the discovery of ongoing hybridization between "modern" and "archaic" populations after the time of the Omo remains, have opened up a renewed debate on the age of H. sapiens in journalistic publications. H. s. idaltu, dated to 160,000 years ago, has been postulated as an extinct subspecies of H. sapiens in 2003. H. neanderthalensis, which became extinct about 40,000 years ago, has also been classified as a subspecies, H. s. neanderthalensis. 

H. 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 close to 800,000 years ago, the approximate time of disappearance of H. antecessor.

Early Homo sapiens

Skhul V (dated at about 80,000–120,000 years old) exhibiting a mix of archaic and modern traits.

 

The term Middle Paleolithic is intended to cover the time between the first emergence of H. sapiens (roughly 300,000 years ago) and the emergence of full behavioral modernity (roughly 50,000 years ago, corresponding to the start of the Upper Paleolithic). 

Many of the early modern human finds, like those of Omo, Herto, Skhul, Jebel Irhoud and Peștera cu Oase exhibit a mix of archaic and modern traits. Skhul V, for example, has prominent brow ridges and a projecting face. However, the brain case is quite rounded and distinct from that of the Neanderthals and is similar to the brain case of modern humans. It is uncertain whether the robust traits of some of the early modern humans like Skhul V reflects mixed ancestry or retention of older traits.

The "gracile" or lightly built skeleton of anatomically modern humans has been connected to a change in behavior, including increased cooperation and "resource transport".

There is evidence that the characteristic human brain development, especially the prefrontal cortex, was due to "an exceptional acceleration of metabolome evolution ... paralleled by a drastic reduction in muscle strength. The observed rapid metabolic changes in brain and muscle, together with the unique human cognitive skills and low muscle performance, might reflect parallel mechanisms in human evolution." The Schöningen spears and their correlation of finds are evidence that complex technological skills already existed 300,000 years ago, and are the first obvious proof of an active (big game) hunt. H. heidelbergensis already had intellectual and cognitive skills like anticipatory planning, thinking and acting that so far have only been attributed to modern man.

The ongoing admixture events within anatomically modern human populations make it difficult to estimate the age of the matrilinear and patrilinear most recent common ancestors of modern populations (Mitochondrial Eve and Y-chromosomal Adam). Estimates of the age of Y-chromosomal Adam have been pushed back significantly with the discovery of an ancient Y-chromosomal lineage in 2013, to likely beyond 300,000 years ago. There have, however, been no reports of the survival of Y-chromosomal or mitochondrial DNA clearly deriving from archaic humans (which would push back the age of the most recent patrilinear or matrilinear ancestor beyond 500,000 years).

Fossil teeth found at Qesem Cave (Israel) and dated to between 400,000 and 200,000 years ago have been compared to the dental material from the younger (120,000–80,000 years ago) Skhul and Qafzeh hominins.

Dispersal and archaic admixture

Overview map of the peopling of the world by anatomically modern humans (numbers indicate dates in thousands of years ago [ka])

 

Dispersal of early H. sapiens begins soon after its emergence, as evidenced by the North African Jebel Irhoud finds (dated to between 280,000 and 350,000 years ago). There is indirect evidence for modern human presence in West Asia around 270,000 years ago and Dali Man from China is dated at 260,000 years ago.

Among extant populations, the Khoi-San (or "Capoid") hunters-gatherers of Southern Africa may represent the human population with the earliest possible divergence within the group Homo sapiens sapiens. Their separation time has been estimated in a 2017 study to be as long as between 260,000 and 350,000 years ago, compatible with the estimated age of H. sapiens. H. s. idaltu, found at Middle Awash in Ethiopia, lived about 160,000 years ago, and H. sapiens lived at Omo Kibish in Ethiopia about 195,000 years ago. Fossil evidence for modern human presence in West Asia is ascertained for 177,000 years ago, and disputed fossil evidence suggests expansion as far as East Asia by 120,000 years ago.

In July 2019, anthropologists reported the discovery of 210,000 year old remains of a H. sapiens and 170,000 year old remains of a H. neanderthalensis in Apidima Cave, Peloponnese, Greece, more than 150,000 years older than previous H. sapiens finds in Europe.

A significant dispersal event, within Africa and to West Asia, is associated with the African megadroughts during MIS 5, beginning 130,000 years ago. A 2011 study located the origin of basal population of contemporary human populations at 130,000 years ago, with the Khoi-San representing an "ancestral population cluster" located in southwestern Africa (near the coastal border of Namibia and Angola).

Layer sequence at Ksar Akil in the Levantine corridor, and discovery of two fossils of Homo sapiens, dated to 40,800 to 39,200 years BP for "Egbert",and 42,400–41,700 BP for "Ethelruda".

 

While early modern human expansion in Sub-Saharan Africa before 130 kya persisted, early expansion to North Africa and Asia appears to have mostly disappeared by the end of MIS5 (75,000 years ago), and is known only from fossil evidence and from archaic admixture. Asia was re-populated by early modern humans in the so-called "recent out-of-Africa migration" post-dating MIS5, beginning around 70,000 years ago. In this expansion, bearers of mt-DNA haplogroup L3 left East Africa, likely reaching Arabia via the Bab-el-Mandeb, and in the Great Coastal Migration spread to South Asia, Maritime South Asia and Oceania by 65,000 years ago, while Europe, East and North Asia, and possibly the Americas, were reached by 50,000 years ago. 

Evidence for the overwhelming contribution of this "recent" (L3-derived) expansion to all non-African populations was established based on mitochondrial DNA, combined with evidence based on physical anthropology of archaic specimens, during the 1990s and 2000s. The assumption of complete replacement has been revised in the 2010s with the discovery of admixture events (introgression) of populations of H. sapiens with populations of archaic humans over the period of between roughly 100,000 and 30,000 years ago, both in Eurasia and in Sub-Saharan Africa. Neanderthal admixture, in the range of 1-4%, is found in all modern populations outside of Africa, including in Europeans, Asians, Papuan New Guineans, Australian Aboriginals, and Native Americans. This suggests that interbreeding between Neanderthals and anatomically modern humans took place after the recent "out of Africa" migration, likely between 60,000 and 40,000 years ago. Recent admixture analyses have added to the complexity, finding that Eastern Neanderthals derive up to 2% of their ancestry from anatomically modern humans who left Africa some 100 kya. The extent of Neanderthal admixture (and introgression of genes acquired by admixture) varies significantly between contemporary racial groups, being absent in Africans, intermediate in Europeans and highest in East Asians. Certain genes related to UV-light adaptation introgressed from Neanderthals have been found to have been selected for in East Asians specifically from 45,000 years ago until around 5,000 years ago. The extent of archaic admixture is of the order of about 1% to 4% in Europeans and East Asians, and highest among Melanesians (Denisova hominin admixture), at 4% to 6%. Cumulatively, about 20% of the Neanderthal genome is estimated to remain present spread in contemporary populations.

Anatomy

Known archaeological remains of Anatomically Modern Humans in Europe and Africa, directly dated, calibrated carbon dates as of 2013.

 

Generally, modern humans are more lightly built (or more "gracile") than the more "robust" archaic humans. Nevertheless, contemporary humans exhibit high variability in many physiological traits, and may exhibit remarkable "robustness". There are still a number of physiological details which can be taken as reliably differentiating the physiology of Neanderthals vs. anatomically modern humans.

Anatomical modernity

The term "anatomically modern humans" (AMH) is used with varying scope depending on context, to distinguish "anatomically modern" Homo sapiens from archaic humans such as Neanderthals and Middle and Lower Paleolithic hominins with transitional features intermediate between H. erectus, Neanderthals and early AMH called archaic Homo sapiens. In a convention popular in the 1990s, Neanderthals were classified as a subspecies of H. sapiens, as H. s. neanderthalensis, while AMH (or European early modern humans, EEMH) was taken to refer to "Cro-Magnon" or H. s. sapiens. Under this nomenclature (Neanderthals considered H. sapiens), the term "anatomically modern Homo sapiens" (AMHS) has also been used to refer to EEMH ("Cro-Magnons"). It has since become more common to designate Neanderthals as a separate species, H. neanderthalensis, so that AMH in the European context refers to H. sapiens (but the question is by no means resolved).

In this more narrow definition of H. sapiens, the subspecies H. s. idaltu, discovered in 2003, also falls under the umbrella of "anatomically modern". The recognition of H. s. idaltu as a valid subspecies of the anatomically modern human lineage would justify the description of contemporary humans with the subspecies name H. s. sapiens. 

A further division of AMH into "early" or "robust" vs. "post-glacial" or "gracile" subtypes has since been used for convenience. The emergence of "gracile AMH" is taken to reflect a process towards a smaller and more fine-boned skeleton beginning around 50,000–30,000 years ago.

Braincase anatomy

Anatomical comparison of skulls of H. sapiens (left) and H. neanderthalensis (right)
(in Cleveland Museum of Natural History)
Features compared are the braincase shape, forehead, browridge, nasal bone, projection, cheek bone angulation, chin and occipital contour

 

The cranium lacks a pronounced occipital bun in the neck, a bulge that anchored considerable neck muscles in Neanderthals. Modern humans, even the earlier ones, generally have a larger fore-brain than the archaic people, so that the brain sits above rather than behind the eyes. This will usually (though not always) give a higher forehead, and reduced brow ridge. Early modern people and some living people do however have quite pronounced brow ridges, but they differ from those of archaic forms by having both a supraorbital foramen or notch, forming a groove through the ridge above each eye. This splits the ridge into a central part and two distal parts. In current humans, often only the central section of the ridge is preserved (if it is preserved at all). This contrasts with archaic humans, where the brow ridge is pronounced and unbroken.

Modern humans commonly have a steep, even vertical forehead whereas their predecessors had foreheads that sloped strongly backwards. According to Desmond Morris, the vertical forehead in humans plays an important role in human communication through eyebrow movements and forehead skin wrinkling.

Brain size in both Neanderthals and AMH is significantly larger on average (but overlapping in range) than brain size in H. erectus. Neanderthal and AMH brain sizes are in the same range, but there are differences in the relative sizes of individual brain areas, with significantly larger visual systems in Neanderthals than in AMH.

Jaw anatomy

Compared to archaic people, anatomically modern humans have smaller, differently shaped teeth. This results in a smaller, more receded dentary, making the rest of the jaw-line stand out, giving an often quite prominent chin. The central part of the mandible forming the chin carries a triangularly shaped area forming the apex of the chin called the mental trigon, not found in archaic humans. Particularly in living populations, the use of fire and tools requires fewer jaw muscles, giving slender, more gracile jaws. Compared to archaic people, modern humans have smaller, lower faces.

Body skeleton structure

The body skeletons of even the earliest and most robustly built modern humans were less robust than those of Neanderthals (and from what little we know from Denisovans), having essentially modern proportions. Particularly regarding the long bones of the limbs, the distal bones (the radius/ulna and tibia/fibula) are nearly the same size or slightly shorter than the proximal bones (the humerus and femur). In ancient people, particularly Neanderthals, the distal bones were shorter, usually thought to be an adaptation to cold climate. The same adaptation can be found in some modern people living in the polar regions.

Height ranges overlap between Neanderthals and AMH, with Neanderthal averages cited as 164 to 168 cm (65 to 66 in) and 152 to 156 cm (60 to 61 in) for males and females, respectively. By comparison, contemporary national averages range between 158 to 184 cm (62 to 72 in) in males and 147 to 172 cm (58 to 68 in) in females. Neanderthal ranges approximate the height distribution measured among Malay people, for one.

Recent evolution

Following the peopling of Africa some 130,000 years ago, and the recent Out-of-Africa expansion some 70,000 to 50,000 years ago, some sub-populations of H. sapiens have been essentially isolated for tens of thousands of years prior to the early modern Age of Discovery. Combined with archaic admixture this has resulted in significant genetic variation, which in some instances has been shown to be the result of directional selection taking place over the past 15,000 years, i.e. significantly later than possible archaic admixture events.

Some climatic adaptations, such as high-altitude adaptation in humans, are thought to have been acquired by archaic admixture. Introgression of genetic variants acquired by Neanderthal admixture have different distributions in European and East Asians, reflecting differences in recent selective pressures. A 2014 study reported that Neanderthal-derived variants found in East Asian populations showed clustering in functional groups related to immune and haematopoietic pathways, while European populations showed clustering in functional groups related to the lipid catabolic process. A 2017 study found correlation of Neanderthal admixture in phenotypic traits in modern European populations.

Physiological or phenotypical changes have been traced to Upper Paleolithic mutations, such as the East Asian variant of the EDAR gene, dated to c. 35,000 years ago.

Recent divergence of Eurasian lineages was sped up significantly during the Last Glacial Maximum, the Mesolithic and the Neolithic, due to increased selection pressures and due to founder effects associated with migration. Alleles predictive of light skin have been found in Neanderthals, but the alleles for light skin in Europeans and East Asians, associated with KITLG and ASIP, are (as of 2012) thought to have not been acquired by archaic admixture but recent mutations since the LGM. Phenotypes associated with the "white" or "Caucasian" populations of Western Eurasian stock emerge during the LGM, from about 19,000 years ago. Average cranial capacity in modern human populations varies in the range of 1,200 to 1,450 cm³ (adult male averages). Larger cranial volume is associated with climatic region, the largest averages being found in populations of Siberia and the Arctic. Both Neanderthal and EEMH had somewhat larger cranial volumes on average than modern Europeans, suggesting the relaxation of selection pressures for larger brain volume after the end of the LGM.

Examples for still later adaptations related to agriculture and animal domestication including East Asian types of ADH1B associated with rice domestication, or lactase persistence, are due to recent selection pressures. 

An even more recent adaptation has been proposed for the Austronesian Sama-Bajau, developed under selection pressures associated with subsisting on freediving over the past thousand years or so.

Behavioral modernity

Lithic Industries of early Homo sapiens at Blombos Cave (M3 phase, MIS 5), Southern Cape, South Africa (c. 105 – 90 Ka)

 

Behavioral modernity, involving the development of language, figurative art and early forms of religion (etc.) is taken to have arisen before 40,000 years ago, marking the beginning of the Upper Paleolithic (in African contexts also known as the Later Stone Age).

There is considerable debate regarding whether the earliest anatomically modern humans behaved similarly to recent or existing humans. Behavioral modernity is taken to include fully developed language (requiring the capacity for abstract thought), artistic expression, early forms of religious behavior, increased cooperation and the formation of early settlements, and the production of articulated tools from lithic cores, bone or antler. The term Upper Paleolithic is intended to cover the period since the rapid expansion of modern humans throughout Eurasia, which coincides with the first appearance of Paleolithic art such as cave paintings and the development of technological innovation such as the spear-thrower. The Upper Paleolithic begins around 50,000 to 40,000 years ago, and also coincides with the disappearance of archaic humans such as the Neanderthals. 

Bifacial silcrete point of early Homo sapiens, from M1 phase (71,000 BCE) layer of Blombos Cave, South Africa

 

The term "behavioral modernity" is somewhat disputed. It is most often used for the set of characteristics marking the Upper Paleolithic, but some scholars use "behavioral modernity" for the emergence of H. sapiens around 200,000 years ago, while others use the term for the rapid developments occurring around 50,000 years ago. It has been proposed that the emergence of behavioral modernity was a gradual process.

In January 2018, it was announced that modern human finds at Misliya cave, Israel, in 2002, had been dated to around 185,000 years ago, the earliest evidence of their out of Africa migration.

The earliest H. sapiens (AMH) found in Europe are the "Cro-Magnon" (named after the site of first discovery in France), beginning about 40,000 to 35,000 years ago. These are also known as "European early modern humans" in contrast to the preceding Neanderthals.

Claimed "Oldest known drawing by human hands", discovered in Blombos Cave in South Africa. Estimated to be a 73,000 years old work of a Homo sapiens.

 

The International Space Station, one of the latest creations of Homo sapiens

 

The equivalent of the Eurasian Upper Paleolithic in African archaeology is known as the Later Stone Age, also beginning roughly 40,000 years ago. While most clear evidence for behavioral modernity uncovered from the later 19th century was from Europe, such as the Venus figurines and other artefacts from the Aurignacian, more recent archaeological research has shown that all essential elements of the kind of material culture typical of contemporary San hunter-gatherers in Southern Africa was also present by least 40,000 years ago, including digging sticks of similar materials used today, ostrich egg shell beads, bone arrow heads with individual maker's marks etched and embedded with red ochre, and poison applicators. There is also a suggestion that "pressure flaking best explains the morphology of lithic artifacts recovered from the c. 75-ka Middle Stone Age levels at Blombos Cave, South Africa. The technique was used during the final shaping of Still Bay bifacial points made on heat‐treated silcrete." Both pressure flaking and heat treatment of materials were previously thought to have occurred much later in prehistory, and both indicate a behaviourally modern sophistication in the use of natural materials. Further reports of research on cave sites along the southern African coast indicate that "the debate as to when cultural and cognitive characteristics typical of modern humans first appeared" may be coming to an end, as "advanced technologies with elaborate chains of production" which "often demand high-fidelity transmission and thus language" have been found at Pinnacle Point Site 5–6. These have been dated to approximately 71,000 years ago. The researchers suggest that their research "shows that microlithic technology originated early in South Africa, evolved over a vast time span (c. 11,000 years), and was typically coupled to complex heat treatment that persisted for nearly 100,000 years. Advanced technologies in Africa were early and enduring; a small sample of excavated sites in Africa is the best explanation for any perceived 'flickering' pattern." These results suggest that Late Stone Age foragers in Sub-Saharan Africa had developed modern cognition and behaviour by at least 50,000 years ago. The change in behavior has been speculated to have been a consequence of an earlier climatic change to much drier and colder conditions between 135,000 and 75,000 years ago. This might have led to human groups who were seeking refuge from the inland droughts, expanded along the coastal marshes rich in shellfish and other resources. Since sea levels were low due to so much water tied up in glaciers, such marshlands would have occurred all along the southern coasts of Eurasia. The use of rafts and boats may well have facilitated exploration of offshore islands and travel along the coast, and eventually permitted expansion to New Guinea and then to Australia.