Poaching

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https://en.wikipedia.org/wiki/Poaching 

 

The Poacher by Frédéric Rouge (1867–1950)

Poaching is the illegal hunting or capturing of wild animals, usually associated with land use rights. Poaching was once performed by impoverished peasants for subsistence purposes and to supplement meager diets. It was set against the hunting privileges of nobility and territorial rulers.

Since the 1980s, the term "poaching" has also been used to refer to the illegal harvesting of wild plants. In agricultural terms, the term 'poaching' is also applied to the loss of soils or grass by the damaging action of feet of livestock, which can affect availability of productive land, water pollution through increased runoff and welfare issues for cattle. Stealing livestock, as in cattle raiding classifies as theft, not as poaching.

The United Nations' Sustainable Development Goal 15 enshrines the sustainable use of all wildlife. It targets the taking of action on dealing with poaching and trafficking of protected species of flora and fauna to ensure their availability for present and future generations.

Legal aspects

The Poacher, 1916 sketch by Tom Thomson, Art Gallery of Ontario, Toronto

In 1998, environmental scientists from the University of Massachusetts Amherst proposed the concept of poaching as an environmental crime and defined as any illegal activity that contravenes the laws and regulations established to protect renewable natural resources, including the illegal harvest of wildlife with the intention of possessing, transporting, consuming or selling it and using its body parts. They considered poaching as one of the most serious threats to the survival of plant and animal populations. Wildlife biologists and conservationists consider poaching to have a detrimental effect on biodiversity both within and outside protected areas as wildlife populations decline, species are depleted locally, and the functionality of ecosystems is disturbed.

Continental Europe

End of the poacher, illustration based on a painting by August Dieffenbacher, 1894

Grave of a poacher in Schliersee, quoting the first stanza of the Jennerwein song. Now and then, poached game is being placed on the grave to commemorate 'Girgl'.

Marterl at the Riederstein, near Baumgartenschneid, Tegernsee. The remains of a poacher, who had never returned from a hunting expedition in 1861, were found at the site in 1897.

Austria and Germany refer to poaching not as theft but as intrusion into third-party hunting rights. While ancient Germanic law allowed any free man, including peasants, to hunt, especially on common land, Roman law restricted hunting to the rulers. In medieval Europe rulers of feudal territories from the king downward tried to enforce exclusive rights of the nobility to hunt and fish on the lands that they ruled. Poaching was deemed a serious crime punishable by imprisonment, but enforcement was comparably weak until the 16th century. Peasants were still allowed to continue small game hunting, but the right of the nobility to hunt was restricted in the 16th century and transferred to land ownership. The low quality of guns made it necessary to approach the game as close as 30 m (100 ft). Poachers in the Salzburg region were typically unmarried men around 30 years of age and usually alone on their illegal trade.

The development of modern hunting rights is closely connected to the comparatively modern idea of exclusive private ownership of land. In the 17th and the 18th centuries, the restrictions on hunting and shooting rights on private property were enforced by gamekeepers and foresters. They denied shared usage of forests, such as resin collection and wood pasture and the peasants right to hunt and fish. However, by end of the 18th century, comparably-easy access to rifles increasingly allowed peasants and servants to poach. Hunting was used in the 18th century as a theatrical demonstration of the aristocratic rule of the land and also had a strong impact on land use patterns. Poaching not only interfered with property rights but also clashed symbolically with the power of the nobility. Between 1830 and 1848, poaching and poaching-related deaths increased in Bavaria. The German revolutions of 1848–49 were interpreted as a general permission for poaching in Bavaria. The reform of the hunting law in 1849 restricted legal hunting to rich landowners and middle classes who could pay hunting fees, which led to disappointment among the general public, who continued to view poachers favourably. Some of the frontier regions, where smuggling was important, showed especially strong resistance to that development. In 1849, the Bavarian military forces were asked to occupy a number of municipalities on the frontier with Austria. Both in Wallgau (now part of Garmisch-Partenkirchen) and in Lackenhäuser, in the Bavarian forest, each household had to feed and accommodate one soldier for a month as part of a military mission to quell the disturbance. The people of Lackenhäuser had several skirmishes with Austrian foresters and military that started due to poached deer. The well-armed people set against the representatives of the state were known as bold poachers (kecke Wilderer). Some poachers and their violent deaths, like Matthias Klostermayr (1736–1771), Georg Jennerwein (1848–1877) and Pius Walder (1952–1982) gained notoriety and have had a strong cultural impact, which has persisted until today. Poaching was used as a dare. It had a certain erotic connotation, as in Franz Schubert's Hunter's love song, (1828, Schubert Thematic Catalogue 909). The lyrics of Franz von Schober connected unlimited hunting with the pursuit of love. Further poaching related legends and stories ranged from the 1821 opera Freischütz to Wolfgang Franz von Kobell's 1871 story about the Brandner Kasper, a Tegernsee locksmith and poacher who struck a special deal with the Grim Reaper.

While poachers had strong local support until the early 20th century, Walder's case showed a significant change in attitudes. Urban citizens still had some sympathy for the hillbilly rebel, but the local community were much supportive.

United Kingdom

Brass plaque on door at Tremedda farm dating to 1868, warning that poachers shall be shot on first sight

Poaching, like smuggling, has a long history in United Kingdom. The verb poach is derived from the Middle English word pocchen literally meaning bagged, enclosed in a bag, which is cognate with "pouch". Poaching was dispassionately reported for England in "Pleas of the Forest", transgressions of the rigid Anglo-Norman forest law. William the Conqueror, who was a great lover of hunting, established and enforced a system of forest law that operated outside the common law and served to protect game animals and their forest habitat from hunting by the common people of England and reserved hunting rights for the new French-speaking Anglo-Norman aristocracy. Henceforth, hunting of game in royal forests by commoners, or in other words poaching, was invariably punishable by death by hanging. In 1087, the poem "The Rime of King William", contained in the Peterborough Chronicle, expressed English indignation at the severe new laws. Poaching was romanticised in literature from the time of the ballads of Robin Hood, as an aspect of the "greenwood" of Merry England. In one tale, Robin Hood is depicted as offering King Richard the Lion Heart venison from deer that was illegally hunted in the Sherwood Forest, the King overlooking the fact that this hunting was a capital offence. The widespread acceptance of the common criminal activity is encapsulated in the observation Non est inquirendum, unde venit venison ("It is not to be inquired, whence comes the venison") that was made by Guillaume Budé in his Traitte de la vénerie. However, the English nobility and land owners were in the long term extremely successful in enforcing the modern concept of property, such as expressed in the enclosures of common land and later in the Highland Clearances, both of which were forced displacement of people from traditional land tenancies and erstwhile-common land. The 19th century saw the rise of acts of legislation, such as the Night Poaching Act 1828 and the Game Act 1831 in the United Kingdom, and various laws elsewhere.

United States

Lady Baltimore, a bald eagle in Alaska survived a poaching attempt in the Juneau Raptor Center mews on 15 August 2015

In North America, the blatant defiance of the laws by poachers escalated to armed conflicts with law authorities, including the Oyster Wars of the Chesapeake Bay and the joint US-British Bering Sea Anti-Poaching Operations of 1891 over the hunting of seals.

Violations of hunting laws and regulations concerning wildlife management, local or international wildlife conservation schemes constitute wildlife crimes that are typically punishable. The following violations and offenses are considered acts of poaching in the US:

• Hunting, killing or collecting wildlife that is listed as endangered by the IUCN and protected by law such as the Endangered Species Act, the Migratory Bird Treaty Act of 1918 and international treaties such as CITES.
• Fishing and hunting without a license.
• Capturing wildlife outside legal hours and outside the hunting season; usually the breeding season is declared as the closed season during which wildlife is protected by law.
• Prohibited use of machine guns, poison, explosives, snare traps, nets and pitfall traps.
• Other offenses of incorrect weaponry, such as the use of cartridge rifles in muzzleloader or archery season or in shotgun-only areas, or the killing of big game animals with insufficient firepower such as .22 Long Rifle rounds.
• Prohibited use of baiting with food, decoys or recorded calls in order to increase chances for shooting wildlife.
• Hunting from a moving vehicle or aircraft.
• Scouting game animals from an aircraft.
• Shining deer with a spotlight at night to impair its natural defenses and thus facilitate an easy kill is considered animal abuse. This hunting method is illegal in California, Virginia, Connecticut, Florida, Michigan, and Tennessee.
• Taking wildlife on land that is restricted, owned by, or licensed to somebody else.
• The animal or plant has been tagged by a researcher.
• Shooting an animal in a confined area (canned hunting).

Africa

Stephen Corry, the director of the human rights group Survival International, has argued that the term "poaching" has at times been used to criminalize the traditional subsistence techniques of indigenous peoples and to bar them from hunting on their ancestral lands when they are declared as wildlife-only zones. Corry argues that parks such as the Central Kalahari Game Reserve are managed for the benefit of foreign tourists and safari groups at the expense of the livelihoods of tribal peoples such as the Kalahari bushmen.

Motives

Sociological and criminological research on poaching indicates that in North America people poach for commercial gain, home consumption, trophies, pleasure, and thrill in killing wildlife or because they disagree with certain hunting regulations, claim a traditional right to hunt, or have negative dispositions toward legal authority. In rural areas of the United States, the key motives for poaching are poverty. Interviews conducted with 41 poachers in the Atchafalaya River basin in Louisiana revealed that 37 of them hunt to provide food for themselves and their families; 11 stated that poaching is part of their personal or cultural history; nine earn money from the sale of poached game to support their families; and eight feel exhilarated and thrilled by outsmarting game wardens.

In rural areas in Africa, the key motives for poaching are the lack of employment opportunities and a limited potential for agriculture and livestock production. Poor people rely on natural resources for their survival and generate cash income through the sale of bushmeat, which attracts high prices in urban centres. Body parts of wildlife are also in demand for traditional medicine and ceremonies. The existence of an international market for poached wildlife implies that well-organised gangs of professional poachers enter vulnerable areas to hunt, and crime syndicates organise the trafficking of wildlife body parts through a complex interlinking network to markets outside the respective countries of origin. Armed conflict in Africa has been linked to intensified poaching and wildlife declines within protected areas, likely reflecting the disruption of traditional livelihoods, which causes people to seek alternative food sources.

Results of an interview survey conducted in several villages in Tanzania indicate that one of the major reasons of poaching is for consumption and sale of bushmeat. Usually, bushmeat is considered a subset of poaching because of the hunting of animals regardless of the laws that conserve certain species of animals. Many families consume more bushmeat if there are no alternative sources of protein available such as fish. The further the families were from the reserve, the less likely they were to illegally hunt wildlife for bushmeat. They were more likely to hunt for bushmeat right before the harvest season and during heavy rains, as before the harvest season, there is not much agricultural work, and heavy rainfall obscures human tracks and makes it easier for poachers to get away with their crimes.

Poverty seems to be a large impetus to cause people to poach, something that affects both residents in Africa and Asia. For example, in Thailand, there are anecdotal accounts of the desire for a better life for children, which drive rural poachers to take the risk of poaching even though they dislike exploiting the wildlife.

Another major cause of poaching is the cultural high demand of wildlife products, such as ivory, which are seen as symbols of status and wealth in China. According to Joseph Vandegrift, China saw an unusual spike in demand for ivory in the 21st century because the economic boom allowed more middle-class Chinese to have a higher purchasing power, which incentivized them to show off their newfound wealth by using ivory, which has been a rare commodity since the Han dynasty.

In China, there are problems with wildlife conservation, specifically relating to tigers. Several authors collaborated on the piece "Public attitude toward tiger farming and tiger conservation in Beijing, China", and explored the option of whether it would be a better policy to raise tigers on a farm or put them in a wildlife conservation habitat to preserve the species. Conducting a survey on 1,058 residents of Beijing, China, with 381 being university students and the other 677 being regular citizens, they tried to gauge public opinion about tigers and conservation efforts for them. They were asked questions regarding the value of tigers in relations to ecology, science, education, aestheticism, and culture. However, one reason emerged as to why tigers are still highly demanded in illegal trading: culturally, they are still status symbols of wealth for the upper class, and they are still thought to have mysterious medicinal and healthcare effects.

Effects

Memorial to rhinos killed by poachers near St Lucia Estuary, South Africa

Further information: Species affected by poaching

The detrimental effects of poaching can include:

• Defaunation of forests: predators, herbivores and fruit-eating vertebrates cannot recover as fast as they are removed from a forest; as their populations decline, the pattern of seed predation and dispersal is altered; tree species with large seeds progressively dominate a forest, while small-seeded plant species become locally extinct.
• Reduction of animal populations in the wild and possible extinction.
• The effective size of protected areas is reduced as poachers use the edges of these areas as open-access resources.
• Wildlife tourism destinations face a negative publicity; those holding a permit for wildlife-based land uses, tourism-based tour and lodging operators lose income; employment opportunities are reduced.
• Emergence of zoonotic diseases caused by transmission of highly variable retrovirus chains:
  • Outbreaks of the Ebola virus in the Congo Basin and in Gabon in the 1990s have been associated with the butchering of apes and consumption of their meat.
  • The outbreak of SARS in Hong Kong is attributed to contact with and consumption of meat from masked palm civets, raccoon dogs, Chinese ferret-badgers and other small carnivores that are available in southern Chinese wildlife markets.
  • Bushmeat hunters in Central Africa infected with the human T-lymphotropic virus were closely exposed to wild primates.
  • Results of research on wild central chimpanzees in Cameroon indicate that they are naturally infected with the simian foamy virus and constitute a reservoir of HIV-1, a precursor of the acquired immunodeficiency syndrome in humans.

Products

A seashell vendor in Tanzania sells seashells to tourists, seashells which have been taken from the sea alive, killing the animal inside.

The body parts of many animals, such as tigers and rhinoceroses, are traditionally believed in some cultures to have certain positive effects on the human body, including increasing virility and curing cancer. These parts are sold in areas where these beliefs are practiced – mostly Asian countries particularly Vietnam and China – on the black market. Such alternative medicial beliefs are pseudoscientific and are not supported by evidence-based medicine.

A vendor selling illegal items at a Chinese market for use in traditional Chinese medicine. Some of the pieces pictured include parts of animals such as a tiger's paw.

Traditional Chinese medicine often incorporates ingredients from all parts of plants, the leaf, stem, flower, root, and also ingredients from animals and minerals. The use of parts of endangered species (such as seahorses, rhinoceros horns, binturong, pangolin scales and tiger bones and claws) has created controversy and resulted in a black market of poachers. Deep-seated cultural beliefs in the potency of tiger parts are so prevalent across China and other east Asian countries that laws protecting even critically endangered species such as the Sumatran tiger fail to stop the display and sale of these items in open markets, according to a 2008 report from TRAFFIC. Popular "medicinal" tiger parts from poached animals include tiger genitals, believed to improve virility, and tiger eyes.

Rhino populations face extinction because of demand in Asia (for traditional medicine and as a luxury item) and in the Middle East (where horns are used for decoration). A sharp surge in demand for rhino horn in Vietnam was attributed to rumors that the horn cured cancer, though this has no basis in science. In 2012, one kilogram of crushed rhino horn has sold for as much as $60,000, more expensive than a kilogram of gold. Vietnam is the only nation which mass-produces bowls made for grinding rhino horn.

Ivory, which is a natural material of several animals, plays a large part in the trade of illegal animal materials and poaching. Ivory is a material used in creating art objects and jewelry where the ivory is carved with designs. China is a consumer of the ivory trade and accounts for a significant amount of ivory sales. In 2012, The New York Times reported on a large upsurge in ivory poaching, with about 70% of all illegal ivory flowing to China.

Fur is also a natural material which is sought after by poachers. A Gamsbart, literally chamois beard, a tuft of hair traditionally worn as a decoration on trachten-hats in the alpine regions of Austria and Bavaria formerly was worn as a hunting (and poaching) trophy. In the past, it was made exclusively from hair from the chamois' lower neck.

Anti-poaching efforts

There are different anti-poaching efforts around the world.

Africa

TRAFFIC brings to light many of the poaching areas and trafficking routes and helps to clamp down on the smuggling routes the poachers use to get the ivory to areas of high demand, predominantly Asia.

As many as 35,000 African elephants are slaughtered yearly to feed the demand for their ivory tusks. This ivory then goes on to be used in jewelry, musical instruments, and other trinkets.

Members of the Rhino Rescue Project have implemented a technique to combat rhino poaching in South Africa by injecting a mixture of indelible dye and a parasiticide into the animals' horns, which enables tracking of the horns and deters consumption of the horn by purchasers. Since rhino horn is made of keratin, advocates say the procedure is painless for the animal.

Another strategy being used to counter rhino poachers in Africa is called RhODIS, which is a database that compiles rhino DNA from confiscated horns and other goods that were being illegally traded, as well as DNA recovered from poaching sites. RhODIS cross-references the DNA as it searches for matches; if a match is found, it is used to track down the poachers.

Africa's Wildlife Trust seeks to protect African elephant populations from poaching activities in Tanzania. Hunting for ivory was banned in 1989, but poaching of elephants continues in many parts of Africa stricken by economic decline. The International Anti-Poaching Foundation has a structured military-like approach to conservation, employing tactics and technology generally reserved for the battlefield. Founder Damien Mander is an advocate of the use of military equipment and tactics, including Unmanned Aerial Vehicles, for military-style anti-poaching operations. Such military-style approaches have been criticised for failing to resolve the underlying reasons for poaching, but to neither tackle "the role of global trading networks" nor the continued demand for animal products. Instead, they "result in coercive, unjust and counterproductive approaches to wildlife conservation".

Chengeta Wildlife is an organization that works to equip and train wildlife protection teams and lobbies African governments to adopt anti-poaching campaigns. Jim Nyamu's elephant walks are part of attempts in Kenya to reduce ivory poaching.

In 2013, the Tanzanian Minister of Natural Resources and Tourism urged that poachers be shot on sight in an effort to stop the mass killing of elephants. Since December 2016, anti-poaching police units in Namibia are permitted to return fire on poachers if fired upon. The government of Botswana adopted a shoot-to-kill policy against poachers in 2013 as a "legitimate conservation strategy" and "a necessary evil", which has reduced poaching to the point it is thought to be "virtually non-existent" in the country, and that neighbouring countries like South Africa should also adopt similar measures in order to save wildlife from extinction. In May 2018, the Kenyan government announced that poachers will face the death penalty, as fines and life imprisonment have "not been deterrence enough to curb poaching, hence the proposed stiffer sentence". Human rights organizations oppose the move, but wildlife advocates support it. Save the Rhino, a UK-based wildlife advocacy organization notes that in Kenya, 23 rhinos and 156 elephants were killed by poachers between 2016 and 2017. As of March 2019, the measure is being put on the fast track to implementation by Kenyan lawmakers.

Asia

Large quantities of ivory are sometimes destroyed as a statement against poaching, a.k.a. "ivory crush". In 2013 the Philippines were the first country to destroy their national seized ivory stock. In 2014, China followed suit and crushed six tons of ivory as a symbolic statement against poaching.

There are two main solutions according to Frederick Chen that would attack the supply side of this poaching problem to reduce its effects: enforcing and enacting more policies and laws for conservation and by encouraging local communities to protect the wildlife around them by giving them more land rights.

Nonetheless, Frederick Chen wrote about two types of effects stemming from demand-side economics: the bandwagon and snob effect. The former deals with people desiring a product due to many other people buying it, while the latter is similar but with one distinct difference: people will clamour to buy something if it denotes wealth that only a few elites could possibly afford. Therefore, the snob effect would offset some of the gains made by anti-poaching laws, regulations, or practices: if a portion of the supply is cut off, the rarity and price of the object would increase, and only a select few would have the desire and purchasing power for it. While approaches to dilute mitigate poaching from a supply-side may not be the best option as people can become more willing to purchase rarer items, especially in countries gaining more wealth and therefore higher demand for illicit goods—Frederick Chen still advocates that we should also focus on exploring ways to reduce the demand for these goods to better stop the problem of poaching. Indeed, there is some evidence that interventions to reduce consumer demand may be more effective for combatting poaching than continually increased policing to catch poachers. However, almost no groups deploying interventions that attempt to reduce consumer demand evaluate the impact of their actions.

Another solution to alleviate poaching proposed in Tigers of the World was about how to implement a multi-lateral strategy that targets different parties to conserve wild tiger populations in general. This multi-lateral approach include working with different agencies to fight and prevent poaching since organized crime syndicates benefit from tiger poaching and trafficking; therefore, there is a need to raise social awareness and implement more protection and investigative techniques. For example, conservation groups raised more awareness amongst park rangers and the local communities to understand the impact of tiger poaching—they achieved this through targeted advertising that would impact the main audience. Targeting advertising using more violent imagery to show the disparity between tigers in nature and as a commodity made a great impact on the general population to combat poaching and indifference towards this problem. The use of spokespeople such as Jackie Chan and other famous Asian actors and models who advocated against poaching also helped the conservation movement for tigers too.

In July 2019, rhino horns encased in plaster were seized in Vietnam that were being trafficked from the United Arab Emirates. Despite the ban on trade since the 1970s, poaching level of rhino horns has risen over the last decade, leading the rhino population into crisis.

Poaching has many causes in both Africa and China. The issue of poaching is not a simple one to solve as traditional methods to counter poaching have not taken into the account the poverty levels that drive some poachers and the lucrative profits made by organized crime syndicates who deal in illegal wildlife trafficking. Conservationists hope the new emerging multi-lateral approach, which would include the public, conservation groups, and the police, will be successful for the future of these animals.

United States

Some game wardens have made use of robotic decoy animals placed in high visibility areas to draw out poachers for arrest after the decoys are shot. Decoys with robotics to mimic natural movements are also in use by law enforcement. The Marine Monitor radar system watches sensitive marine areas for illicit vessel movement.

Cartesian doubt

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Cartesian_doubt

Cartesian doubt is a form of methodological skepticism associated with the writings and methodology of René Descartes (March 31, 1596–Feb 11, 1650). Cartesian doubt is also known as Cartesian skepticism, methodic doubt, methodological skepticism, universal doubt, systematic doubt, or hyperbolic doubt.

Cartesian doubt is a systematic process of being skeptical about (or doubting) the truth of one's beliefs, which has become a characteristic method in philosophy. Additionally, Descartes' method has been seen by many as the root of the modern scientific method. This method of doubt was largely popularized in Western philosophy by René Descartes, who sought to doubt the truth of all beliefs in order to determine which he could be certain were true. It is the basis for Descartes' statement, "Cogito ergo sum" (I think, therefore I am). A fuller version of his phrase: "dubito ergo cogito, cogito ergo sum" translates to "I doubt therefore I think, I think therefore I exist." Sum translated as "I exist" (per various Latin to English dictionaries) presents a much larger and clearer meaning to the phrase.

Methodological skepticism is distinguished from philosophical skepticism in that methodological skepticism is an approach that subjects all knowledge claims to scrutiny with the goal of sorting out true from false claims, whereas philosophical skepticism is an approach that questions the possibility of certain knowledge.

Characteristics

Cartesian doubt is methodological. It uses doubt as a route to certain knowledge by identifying what can't be doubted. The fallibility of sense data in particular is a subject of Cartesian doubt.

There are several interpretations as to the objective of Descartes' skepticism. Prominent among these is a foundationalist account, which claims that Descartes' skepticism aims to eliminate all belief that it is possible to doubt, thus leaving only basic beliefs (also known as foundational beliefs). From these indubitable basic beliefs, Descartes then attempts to derive further knowledge. It's an archetypal and significant example that epitomizes the Continental Rational schools of philosophy.

Mario Bunge argues that methodological skepticism presupposes that scientific theories and methods satisfy certain philosophical requirements: Idealism, materialism, realism, rationalism, empiricism, and systemism, that the data and hypotheses of science constitute a system.

Technique

Descartes' method of hyperbolic doubt included:

• Accepting only information you know is true
• Breaking down these truths into smaller units
• Solving the simple problems first
• Making complete lists of further problems

Hyperbolic doubt means having the tendency to doubt, since it is an extreme or exaggerated form of doubt. Knowledge in the Cartesian sense means to know something beyond not merely all reasonable doubt, but all possible doubt. In his Meditations on First Philosophy (1641), Descartes resolved to systematically doubt that any of his beliefs were true, in order to build, from the ground up, a belief system consisting of only certainly true beliefs; his end goal—or at least a major one—was to find an undoubtable basis for the sciences. Consider Descartes' opening lines of the Meditations:

Several years have now elapsed since I first became aware that I had accepted, even from my youth, many false opinions for true, and that consequently what I afterward based on such principles was highly doubtful; and from that time I was convinced of the necessity of undertaking once in my life to rid myself of all the opinions I had adopted, and of commencing anew the work of building from the foundation...—Descartes, Meditation I, 1641

Descartes' method

René Descartes, the originator of Cartesian doubt, put all beliefs, ideas, thoughts, and matter in doubt. He showed that his grounds, or reasoning, for any knowledge could just as well be false. Sensory experience, the primary mode of knowledge, is often erroneous and therefore must be doubted. For instance, what one is seeing may very well be a hallucination. There is nothing that proves it cannot be. In short, if there is any way a belief can be disproved, then its grounds are insufficient. From this, Descartes proposed two arguments, the dream and the demon.

The dream argument

See also: Dream argument

Descartes, knowing that the context of our dreams, while possibly unbelievable, are often lifelike, hypothesized that humans can only believe that they are awake. There are no sufficient grounds to distinguish a dream experience from a waking experience. For instance, Subject A sits at the computer, typing this article. Just as much evidence exists to indicate that the act of composing this article is reality as there is evidence to demonstrate the opposite. Descartes conceded that we live in a world that can create such ideas as dreams. However, by the end of The Meditations, he concludes that we can distinguish dream from reality at least in retrospect:

"But when I distinctly see where things come from and where and when they come to me, and when I can connect my perceptions of them with the whole of the rest of my life without a break, then I am quite certain that when I encounter these things I am not asleep but awake."—Descartes: Selected Philosophical Writings

The Evil Demon

Main article: Evil demon

Descartes reasoned that our very own experience may very well be controlled by an evil demon of sorts. This demon is as clever and deceitful as he is powerful. He could have created a superficial world that we may think we live in. As a result of this doubt, sometimes termed the Malicious Demon Hypothesis, Descartes found that he was unable to trust even the simplest of his perceptions.

In Meditation I, Descartes stated that if one were mad, even briefly, the insanity might have driven man into believing that what we thought was true could be merely our minds deceiving us. He also stated that there could be 'some malicious, powerful, cunning demon' that had deceived us, preventing us from judging correctly.

Descartes argued that all his senses were lying, and since your senses can easily fool you, his idea of an infinitely powerful being must be true—since that idea could have only been put there by an infinitely powerful being who would have no reason for deceit.

I think, therefore I am

While methodic doubt has a nature, one need not hold that knowledge is impossible to apply the method of doubt. Indeed, Descartes' attempt to apply the method of doubt to the existence of himself spawned the proof of his famous saying, "Cogito, ergo sum" (I think, therefore I am). That is, Descartes tried to doubt his own existence, but found that even his doubting showed that he existed, since he could not doubt if he did not exist.

Analytic–synthetic distinction

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Analytic%E2%80%93synthetic_distinction

The analytic–synthetic distinction is a semantic distinction used primarily in philosophy to distinguish between propositions (in particular, statements that are affirmative subject–predicate judgments) that are of two types: analytic propositions and synthetic propositions. Analytic propositions are true or not true solely by virtue of their meaning, whereas synthetic propositions' truth, if any, derives from how their meaning relates to the world.

While the distinction was first proposed by Immanuel Kant, it was revised considerably over time, and different philosophers have used the terms in very different ways. Furthermore, some philosophers (starting with Willard Van Orman Quine) have questioned whether there is even a clear distinction to be made between propositions which are analytically true and propositions which are synthetically true. Debates regarding the nature and usefulness of the distinction continue to this day in contemporary philosophy of language.

Kant

Immanuel Kant

Conceptual containment

The philosopher Immanuel Kant uses the terms "analytic" and "synthetic" to divide propositions into two types. Kant introduces the analytic–synthetic distinction in the Introduction to his Critique of Pure Reason (1781/1998, A6–7/B10–11). There, he restricts his attention to statements that are affirmative subject–predicate judgments and defines "analytic proposition" and "synthetic proposition" as follows:

• analytic proposition: a proposition whose predicate concept is contained in its subject concept
• synthetic proposition: a proposition whose predicate concept is not contained in its subject concept but related

Examples of analytic propositions, on Kant's definition, include:

• "All bachelors are unmarried."
• "All triangles have three sides."

Kant's own example is:

• "All bodies are extended": that is, they occupy space. (A7/B11)

Each of these statements is an affirmative subject–predicate judgment, and, in each, the predicate concept is contained within the subject concept. The concept "bachelor" contains the concept "unmarried"; the concept "unmarried" is part of the definition of the concept "bachelor". Likewise, for "triangle" and "has three sides", and so on.

Examples of synthetic propositions, on Kant's definition, include:

• "All bachelors are alone."
• "All creatures with hearts have kidneys."

Kant's own example is:

• "All bodies are heavy": that is, they experience a gravitational force. (A7/B11)

As with the previous examples classified as analytic propositions, each of these new statements is an affirmative subject–predicate judgment. However, in none of these cases does the subject concept contain the predicate concept. The concept "bachelor" does not contain the concept "alone"; "alone" is not a part of the definition of "bachelor". The same is true for "creatures with hearts" and "have kidneys"; even if every creature with a heart also has kidneys, the concept "creature with a heart" does not contain the concept "has kidneys". So the philosophical issue is: What kind of statement is "Language is used to transmit meaning"?

Kant's version and the a priori–a posteriori distinction

Main article: A priori and a posteriori

In the Introduction to the Critique of Pure Reason, Kant contrasts his distinction between analytic and synthetic propositions with another distinction, the distinction between a priori and a posteriori propositions. He defines these terms as follows:

• a priori proposition: a proposition whose justification does not rely upon experience. Moreover, the proposition can be validated by experience, but is not grounded in experience. Therefore, it is logically necessary.
• a posteriori proposition: a proposition whose justification does rely upon experience. The proposition is validated by, and grounded in, experience. Therefore, it is logically contingent.

Examples of a priori propositions include:

• "All bachelors are unmarried."
• "7 + 5 = 12."

The justification of these propositions does not depend upon experience: one need not consult experience to determine whether all bachelors are unmarried, nor whether 7 + 5 = 12. (Of course, as Kant would grant, experience is required to understand the concepts "bachelor", "unmarried", "7", "+" and so forth. However, the a priori–a posteriori distinction as employed here by Kant refers not to the origins of the concepts but to the justification of the propositions. Once we have the concepts, experience is no longer necessary.)

Examples of a posteriori propositions include:

• "All bachelors are unhappy."
• "Tables exist."

Both of these propositions are a posteriori: any justification of them would require one's experience.

The analytic–synthetic distinction and the a priori–a posteriori distinction together yield four types of propositions:

• analytic a priori
• synthetic a priori
• analytic a posteriori
• synthetic a posteriori

Kant posits the third type as obviously self-contradictory. Ruling it out, he discusses only the remaining three types as components of his epistemological framework—each, for brevity's sake, becoming, respectively, "analytic", "synthetic a priori", and "empirical" or "a posteriori" propositions. This triad accounts for all propositions possible. Examples of analytic and a posteriori statements have already been given, for synthetic a priori propositions he gives those in mathematics and physics.

The ease of knowing analytic propositions

Part of Kant's argument in the Introduction to the Critique of Pure Reason involves arguing that there is no problem figuring out how knowledge of analytic propositions is possible. To know an analytic proposition, Kant argued, one need not consult experience. Instead, one needs merely to take the subject and "extract from it, in accordance with the principle of contradiction, the required predicate" (A7/B12). In analytic propositions, the predicate concept is contained in the subject concept. Thus, to know an analytic proposition is true, one need merely examine the concept of the subject. If one finds the predicate contained in the subject, the judgment is true.

Thus, for example, one need not consult experience to determine whether "All bachelors are unmarried" is true. One need merely examine the subject concept ("bachelors") and see if the predicate concept "unmarried" is contained in it. And in fact, it is: "unmarried" is part of the definition of "bachelor" and so is contained within it. Thus the proposition "All bachelors are unmarried" can be known to be true without consulting experience.

It follows from this, Kant argued, first: All analytic propositions are a priori; there are no a posteriori analytic propositions. It follows, second: There is no problem understanding how we can know analytic propositions; we can know them because we only need to consult our concepts in order to determine that they are true.

The possibility of metaphysics

After ruling out the possibility of analytic a posteriori propositions, and explaining how we can obtain knowledge of analytic a priori propositions, Kant also explains how we can obtain knowledge of synthetic a posteriori propositions. That leaves only the question of how knowledge of synthetic a priori propositions is possible. This question is exceedingly important, Kant maintains, because all scientific knowledge (for him Newtonian physics and mathematics) is made up of synthetic a priori propositions. If it is impossible to determine which synthetic a priori propositions are true, he argues, then metaphysics as a discipline is impossible. The remainder of the Critique of Pure Reason is devoted to examining whether and how knowledge of synthetic a priori propositions is possible.

Logical positivists

Frege revision of Kantian definition

Over a hundred years later, a group of philosophers took interest in Kant and his distinction between analytic and synthetic propositions: the logical positivists.

Part of Kant's examination of the possibility of synthetic a priori knowledge involved the examination of mathematical propositions, such as

• "7 + 5 = 12." (B15–16)
• "The shortest distance between two points is a straight line." (B16–17)

Kant maintained that mathematical propositions such as these are synthetic a priori propositions, and that we know them. That they are synthetic, he thought, is obvious: the concept "equal to 12" is not contained within the concept "7 + 5"; and the concept "straight line" is not contained within the concept "the shortest distance between two points". From this, Kant concluded that we have knowledge of synthetic a priori propositions.

Gottlob Frege's notion of analyticity included a number of logical properties and relations beyond containment: symmetry, transitivity, antonymy, or negation and so on. He had a strong emphasis on formality, in particular formal definition, and also emphasized the idea of substitution of synonymous terms. "All bachelors are unmarried" can be expanded out with the formal definition of bachelor as "unmarried man" to form "All unmarried men are unmarried", which is recognizable as tautologous and therefore analytic from its logical form: any statement of the form "All X that are (F and G) are F". Using this particular expanded idea of analyticity, Frege concluded that Kant's examples of arithmetical truths are analytical a priori truths and not synthetic a priori truths.

Thanks to Frege's logical semantics, particularly his concept of analyticity, arithmetic truths like "7+5=12" are no longer synthetic a priori but analytical a priori truths in Carnap's extended sense of "analytic". Hence logical empiricists are not subject to Kant's criticism of Hume for throwing out mathematics along with metaphysics.

(Here "logical empiricist" is a synonym for "logical positivist".)

The origin of the logical positivist's distinction

The logical positivists agreed with Kant that we have knowledge of mathematical truths, and further that mathematical propositions are a priori. However, they did not believe that any complex metaphysics, such as the type Kant supplied, are necessary to explain our knowledge of mathematical truths. Instead, the logical positivists maintained that our knowledge of judgments like "all bachelors are unmarried" and our knowledge of mathematics (and logic) are in the basic sense the same: all proceeded from our knowledge of the meanings of terms or the conventions of language.

Since empiricism had always asserted that all knowledge is based on experience, this assertion had to include knowledge in mathematics. On the other hand, we believed that with respect to this problem the rationalists had been right in rejecting the old empiricist view that the truth of "2+2=4" is contingent on the observation of facts, a view that would lead to the unacceptable consequence that an arithmetical statement might possibly be refuted tomorrow by new experiences. Our solution, based upon Wittgenstein's conception, consisted in asserting the thesis of empiricism only for factual truth. By contrast, the truths of logic and mathematics are not in need of confirmation by observations, because they do not state anything about the world of facts, they hold for any possible combination of facts.

— Rudolf Carnap, "Autobiography": §10: Semantics, p. 64

Logical positivist definitions

Thus the logical positivists drew a new distinction, and, inheriting the terms from Kant, named it the "analytic-synthetic distinction". They provided many different definitions, such as the following:

• analytic proposition: a proposition whose truth depends solely on the meaning of its terms
• analytic proposition: a proposition that is true (or false) by definition
• analytic proposition: a proposition that is made true (or false) solely by the conventions of language

(While the logical positivists believed that the only necessarily true propositions were analytic, they did not define "analytic proposition" as "necessarily true proposition" or "proposition that is true in all possible worlds".)

Synthetic propositions were then defined as:

• synthetic proposition: a proposition that is not analytic

These definitions applied to all propositions, regardless of whether they were of subject–predicate form. Thus, under these definitions, the proposition "It is raining or it is not raining" was classified as analytic, while for Kant it was analytic by virtue of its logical form. And the proposition "7 + 5 = 12" was classified as analytic, while under Kant's definitions it was synthetic.

Two-dimensionalism

Two-dimensionalism is an approach to semantics in analytic philosophy. It is a theory of how to determine the sense and reference of a word and the truth-value of a sentence. It is intended to resolve a puzzle that has plagued philosophy for some time, namely: How is it possible to discover empirically that a necessary truth is true? Two-dimensionalism provides an analysis of the semantics of words and sentences that makes sense of this possibility. The theory was first developed by Robert Stalnaker, but it has been advocated by numerous philosophers since, including David Chalmers and Berit Brogaard.

Any given sentence, for example, the words,

"Water is H₂O"

is taken to express two distinct propositions, often referred to as a primary intension and a secondary intension, which together compose its meaning.

The primary intension of a word or sentence is its sense, i.e., is the idea or method by which we find its referent. The primary intension of "water" might be a description, such as watery stuff. The thing picked out by the primary intension of "water" could have been otherwise. For example, on some other world where the inhabitants take "water" to mean watery stuff, but, where the chemical make-up of watery stuff is not H₂O, it is not the case that water is H₂O for that world.

The secondary intension of "water" is whatever thing "water" happens to pick out in this world, whatever that world happens to be. So if we assign "water" the primary intension watery stuff then the secondary intension of "water" is H₂O, since H₂O is watery stuff in this world. The secondary intension of "water" in our world is H₂O, which is H₂O in every world because unlike watery stuff it is impossible for H₂O to be other than H₂O. When considered according to its secondary intension, "Water is H₂O" is true in every world.

If two-dimensionalism is workable it solves some very important problems in the philosophy of language. Saul Kripke has argued that "Water is H₂O" is an example of the necessary a posteriori, since we had to discover that water was H₂O, but given that it is true, it cannot be false. It would be absurd to claim that something that is water is not H₂O, for these are known to be identical.

Carnap's distinction

Rudolf Carnap was a strong proponent of the distinction between what he called "internal questions", questions entertained within a "framework" (like a mathematical theory), and "external questions", questions posed outside any framework – posed before the adoption of any framework. The "internal" questions could be of two types: logical (or analytic, or logically true) and factual (empirical, that is, matters of observation interpreted using terms from a framework). The "external" questions were also of two types: those that were confused pseudo-questions ("one disguised in the form of a theoretical question") and those that could be re-interpreted as practical, pragmatic questions about whether a framework under consideration was "more or less expedient, fruitful, conducive to the aim for which the language is intended". The adjective "synthetic" was not used by Carnap in his 1950 work Empiricism, Semantics, and Ontology. Carnap did define a "synthetic truth" in his work Meaning and Necessity: a sentence that is true, but not simply because "the semantical rules of the system suffice for establishing its truth".

The notion of a synthetic truth is of something that is true both because of what it means and because of the way the world is, whereas analytic truths are true in virtue of meaning alone. Thus, what Carnap calls internal factual statements (as opposed to internal logical statements) could be taken as being also synthetic truths because they require observations, but some external statements also could be "synthetic" statements and Carnap would be doubtful about their status. The analytic–synthetic argument therefore is not identical with the internal–external distinction.

Quine's criticisms

See also: Willard Van Orman Quine § Rejection of the analytic–synthetic distinction, and Two Dogmas of Empiricism § Analyticity and circularity

In 1951, Willard Van Orman Quine published the essay "Two Dogmas of Empiricism" in which he argued that the analytic–synthetic distinction is untenable. The argument at bottom is that there are no "analytic" truths, but all truths involve an empirical aspect. In the first paragraph, Quine takes the distinction to be the following:

• analytic propositions – propositions grounded in meanings, independent of matters of fact.
• synthetic propositions – propositions grounded in fact.

Quine's position denying the analytic–synthetic distinction is summarized as follows:

It is obvious that truth in general depends on both language and extralinguistic fact. ... Thus one is tempted to suppose in general that the truth of a statement is somehow analyzable into a linguistic component and a factual component. Given this supposition, it next seems reasonable that in some statements the factual component should be null; and these are the analytic statements. But, for all its a priori reasonableness, a boundary between analytic and synthetic statements simply has not been drawn. That there is such a distinction to be drawn at all is an unempirical dogma of empiricists, a metaphysical article of faith.

— Willard V. O. Quine, "Two Dogmas of Empiricism", p. 64

To summarize Quine's argument, the notion of an analytic proposition requires a notion of synonymy, but establishing synonymy inevitably leads to matters of fact – synthetic propositions. Thus, there is no non-circular (and so no tenable) way to ground the notion of analytic propositions.

While Quine's rejection of the analytic–synthetic distinction is widely known, the precise argument for the rejection and its status is highly debated in contemporary philosophy. However, some (for example, Paul Boghossian) argue that Quine's rejection of the distinction is still widely accepted among philosophers, even if for poor reasons.

Responses

Paul Grice and P. F. Strawson criticized "Two Dogmas" in their 1956 article "In Defense of a Dogma". Among other things, they argue that Quine's skepticism about synonyms leads to a skepticism about meaning. If statements can have meanings, then it would make sense to ask "What does it mean?". If it makes sense to ask "What does it mean?", then synonymy can be defined as follows: Two sentences are synonymous if and only if the true answer of the question "What does it mean?" asked of one of them is the true answer to the same question asked of the other. They also draw the conclusion that discussion about correct or incorrect translations would be impossible given Quine's argument. Four years after Grice and Strawson published their paper, Quine's book Word and Object was released. In the book Quine presented his theory of indeterminacy of translation.

In Speech Acts, John Searle argues that from the difficulties encountered in trying to explicate analyticity by appeal to specific criteria, it does not follow that the notion itself is void. Considering the way which we would test any proposed list of criteria, which is by comparing their extension to the set of analytic statements, it would follow that any explication of what analyticity means presupposes that we already have at our disposal a working notion of analyticity.

In "'Two Dogmas' Revisited", Hilary Putnam argues that Quine is attacking two different notions:

It seems to me there is as gross a distinction between 'All bachelors are unmarried' and 'There is a book on this table' as between any two things in this world, or at any rate, between any two linguistic expressions in the world;

— Hilary Putnam, Philosophical Papers, p. 36

Analytic truth defined as a true statement derivable from a tautology by putting synonyms for synonyms is near Kant's account of analytic truth as a truth whose negation is a contradiction. Analytic truth defined as a truth confirmed no matter what, however, is closer to one of the traditional accounts of a priori. While the first four sections of Quine's paper concern analyticity, the last two concern a priority. Putnam considers the argument in the two last sections as independent of the first four, and at the same time as Putnam criticizes Quine, he also emphasizes his historical importance as the first top rank philosopher to both reject the notion of a priority and sketch a methodology without it.

Jerrold Katz, a one-time associate of Noam Chomsky, countered the arguments of "Two Dogmas" directly by trying to define analyticity non-circularly on the syntactical features of sentences. Chomsky himself critically discussed Quine's conclusion, arguing that it is possible to identify some analytic truths (truths of meaning, not truths of facts) which are determined by specific relations holding among some innate conceptual features of the mind or brain.

In Philosophical Analysis in the Twentieth Century, Volume 1: The Dawn of Analysis, Scott Soames pointed out that Quine's circularity argument needs two of the logical positivists' central theses to be effective:

All necessary (and all a priori) truths are analytic.

Analyticity is needed to explain and legitimate necessity.

It is only when these two theses are accepted that Quine's argument holds. It is not a problem that the notion of necessity is presupposed by the notion of analyticity if necessity can be explained without analyticity. According to Soames, both theses were accepted by most philosophers when Quine published "Two Dogmas". Today, however, Soames holds both statements to be antiquated. He says: "Very few philosophers today would accept either [of these assertions], both of which now seem decidedly antique."

In other fields

This distinction was imported from philosophy into theology, with Albrecht Ritschl attempting to demonstrate that Kant's epistemology was compatible with Lutheranism.

Y-chromosomal Adam

From Wikipedia, the free encyclopedia

https://en.wikipedia.org/wiki/Y-chromosomal_Adam 

In human genetics, the Y-chromosomal most recent common ancestor (Y-MRCA, informally known as Y-chromosomal Adam) is the patrilineal most recent common ancestor (MRCA) from whom all currently living humans are descended. He is the most recent male from whom all living humans are descended through an unbroken line of their male ancestors. The term Y-MRCA reflects the fact that the Y chromosomes of all currently living human males are directly derived from the Y chromosome of this remote ancestor. The analogous concept of the matrilineal most recent common ancestor is known as "Mitochondrial Eve" (mt-MRCA, named for the matrilineal transmission of mtDNA), the most recent woman from whom all living humans are descended matrilineally. As with "Mitochondrial Eve", the title of "Y-chromosomal Adam" is not permanently fixed to a single individual, but can advance over the course of human history as paternal lineages become extinct.

Estimates of the time when Y-MRCA lived have also shifted as modern knowledge of human ancestry changes. For example, in 2013, the discovery of a previously unknown Y-chromosomal haplogroup was announced, which resulted in a slight adjustment of the estimated age of the human Y-MRCA.

By definition, it is not necessary that the Y-MRCA and the mt-MRCA should have lived at the same time. While estimates as of 2014 suggested the possibility that the two individuals may well have been roughly contemporaneous, the discovery of the archaic Y-haplogroup has pushed back the estimated age of the Y-MRCA beyond the most likely age of the mt-MRCA. As of 2015, estimates of the age of the Y-MRCA range around 200,000 to 300,000 years ago, roughly consistent with the emergence of anatomically modern humans.

Y-chromosomal data taken from a Neanderthal from El Sidrón, Spain, produced a Y-T-MRCA of 588,000 years ago for Neanderthal and Homo sapiens patrilineages, dubbed ante Adam, and 275,000 years ago for Y-MRCA.

Definition

Hominin timeline
−10 — – −9 — – −8 — – −7 — – −6 — – −5 — – −4 — – −3 — – −2 — – −1 — – 0 —	Miocene Pliocene Pleistocene Hominini Nakalipithecus Samburupithecus Ouranopithecus (Ou. turkae) (Ou. macedoniensis) Chororapithecus Oreopithecus Sivapithecus Sahelanthropus Graecopithecus Orrorin (O. praegens) (O. tugenensis) Ardipithecus (Ar. kadabba) (Ar. ramidus) Australopithecus (Au. africanus) (Au. afarensis) (Au. anamensis) H. habilis (H. rudolfensis) (Au. garhi) H. erectus (H. antecessor) (H. ergaster) (Au. sediba) H. heidelbergensis Homo sapiens Neanderthals Denisovans	← Earlier apes ← Gorilla split ← Chimpanzee split ← Earliest bipedal ← Earliest sign of Ardipithecus ← Earliest sign of Australopithecus ← Earliest stone tools ← Earliest sign of Homo ← Dispersal beyond Africa ← Earliest fire / cooking ← Earliest rock art ← Earliest clothes ← Modern humans H o m i n i d s P a r a n t h r o p u s
(million years ago)

Main article: MRCA

The Y-chromosomal most recent common ancestor is the most recent common ancestor of the Y-chromosomes found in currently living human males.

Due to the definition via the "currently living" population, the identity of a MRCA, and by extension of the human Y-MRCA, is time-dependent (it depends on the moment in time intended by the term "currently"). The MRCA of a population may move forward in time as archaic lineages within the population go extinct: once a lineage has died out, it is irretrievably lost. This mechanism can thus only shift the title of Y-MRCA forward in time. Such an event could be due to the total extinction of several basal haplogroups. The same holds for the concepts of matrilineal and patrilineal MRCAs: it follows from the definition of Y-MRCA that he had at least two sons who both have unbroken lineages that have survived to the present day. If the lineages of all but one of those sons die out, then the title of Y-MRCA shifts forward from the remaining son through his patrilineal descendants, until the first descendant is reached who had at least two sons who both have living, patrilineal descendants. The title of Y-MRCA is not permanently fixed to a single individual, and the Y-MRCA for any given population would himself have been part of a population which had its own, more remote, Y-MRCA.

Although the informal name "Y-chromosomal Adam" is a reference to the biblical Adam, this should not be misconstrued as implying that the bearer of the chromosome was the only human male alive during his time. His other male contemporaries may also have descendants alive today, but not, by definition, through solely patrilineal descent; in other words, none of them have an unbroken male line of descendants (son's son's son's … son) connecting them to currently living people.

By the nature of the concept of most recent common ancestors, these estimates can only represent a terminus ante quem ("limit before which"), until the genome of the entire population has been examined (in this case, the genome of all living humans).

Age estimate

Estimates on the age of the Y-MRCA crucially depend on the most archaic known haplogroup extant in contemporary populations. As of 2018, this is haplogroup A00 (discovered in 2013). Age estimates based on this published during 2014–2015 range between 160,000 and 300,000 years, compatible with the time of emergence and early dispersal of Homo sapiens.

Method

In addition to the tendency of the title of Y-MRCA to shift forward in time, the estimate of the Y-MRCA's DNA sequence, his position in the family tree, the time when he lived, and his place of origin, are all subject to future revisions.

The following events would change the estimate of who the individual designated as Y-MRCA was:

• Further sampling of Y chromosomes could uncover previously unknown divergent lineages. If this happens, Y-chromosome lineages would converge on an individual who lived further back in time.
• The discovery of additional deep rooting mutations in known lineages could lead to a rearrangement of the family tree.
• Revision of the Y-chromosome mutation rate (see below) can change the estimate of the time when he lived.

The time when Y-MRCA lived is determined by applying a molecular clock to human Y-chromosomes. In contrast to mitochondrial DNA (mtDNA), which has a short sequence of 16,000 base pairs, and mutates frequently, the Y chromosome is significantly longer at 60 million base pairs, and has a lower mutation rate. These features of the Y chromosome have slowed down the identification of its polymorphisms; as a consequence, they have reduced the accuracy of Y-chromosome mutation rate estimates.

Methods of estimating the age of the Y-MRCA for a population of human males whose Y-chromosomes have been sequenced are based on applying the theories of molecular evolution to the Y chromosome. Unlike the autosomes, the human Y-chromosome does not recombine often with the X chromosome during meiosis, but is usually transferred intact from father to son; however, it can recombine with the X chromosome in the pseudoautosomal regions at the ends of the Y chromosome. Mutations occur periodically within the Y chromosome, and these mutations are passed on to males in subsequent generations.

These mutations can be used as markers to identify shared patrilineal relationships. Y chromosomes that share a specific mutation are referred to as haplogroups. Y chromosomes within a specific haplogroup are assumed to share a common patrilineal ancestor who was the first to carry the defining mutation. (This assumption could be mistaken, as it is possible for the same mutation to occur more than once.) A family tree of Y chromosomes can be constructed, with the mutations serving as branching points along lineages. The Y-MRCA is positioned at the root of the family tree, as the Y chromosomes of all living males are descended from his Y chromosome.

Researchers can reconstruct ancestral Y chromosome DNA sequences by reversing mutated DNA segments to their original condition. The most likely original or ancestral state of a DNA sequence is determined by comparing human DNA sequences with those of a closely related species, usually non-human primates such as chimpanzees and gorillas. By reversing known mutations in a Y-chromosome lineage, a hypothetical ancestral sequence for the MRCA, Y-chromosomal Adam, can be inferred.

Determining the Y-MRCA's DNA sequence, and the time when he lived, involves identifying the human Y-chromosome lineages that are most divergent from each other—the lineages that share the fewest mutations with each other when compared to a non-human primate sequence in a phylogenetic tree. The common ancestor of the most divergent lineages is therefore the common ancestor of all lineages.

History of estimates

Early estimates of the age for the Y-MRCA published during the 1990s ranged between roughly 200 and 300 thousand years ago (kya).Such estimates were later substantially revised downward, as in Thomson et al. 2000, which proposed an age of about 59,000. This date suggested that the Y-MRCA lived about 84,000 years after his female counterpart mt-MRCA (the matrilineal most recent common ancestor), who lived 150,000–200,000 years ago. This date also meant that Y-chromosomal Adam lived at a time very close to, and possibly after, the migration from Africa which is believed to have taken place 50,000–80,000 years ago. One explanation given for this discrepancy in the time depths of patrilineal vs. matrilineal lineages was that females have a better chance of reproducing than males due to the practice of polygyny. When a male individual has several wives, he has effectively prevented other males in the community from reproducing and passing on their Y chromosomes to subsequent generations. On the other hand, polygyny does not prevent most females in a community from passing on their mitochondrial DNA to subsequent generations. This differential reproductive success of males and females can lead to fewer male lineages relative to female lineages persisting into the future. These fewer male lineages are more sensitive to drift and would most likely coalesce on a more recent common ancestor. This would potentially explain the more recent dates associated with the Y-MRCA.

The "hyper-recent" estimate of significantly below 100 kya was again corrected upward in studies of the early 2010s, which ranged at about 120 kya to 160 kya. This revision was due to the rearrangement of the backbone of the Y-chromosome phylogeny following the resequencing of Haplogroup A lineages. In 2013, Francalacci et al. reported the sequencing of male-specific single-nucleotide Y-chromosome polymorphisms (MSY-SNPs) from 1204 Sardinian males, which indicated an estimate of 180,000 to 200,000 years for the common origin of all humans through paternal lineage. Also in 2013, Poznik et al. reported the Y-MRCA to have lived between 120,000 and 156,000 years ago, based on genome sequencing of 69 men from 9 different populations. In addition, the same study estimated the age of Mitochondrial Eve to about 99,000 and 148,000 years. As these ranges overlap for a time-range of 28,000 years (148 to 120 kya), the results of this study have been cast in terms of the possibility that "Genetic Adam and Eve may have walked on Earth at the same time" in the popular press.

The announcement by Mendez et al. of the discovery of a previously unknown lineage, haplogroup A00, in 2013, resulted in another shift in the estimate for the age of Y-chromosomal Adam. The authors estimated the split from the other haplogroups at 338,000 years ago (95% confidence interval 237–581 kya), but later Elhaik et al. (2014) dated it to between 163,900 and 260,200 years ago (95% CI), and Karmin et al. (2015) dated it to between 192,000 and 307,000 years ago (95% CI). The same study reports that non-African populations converge to a cluster of Y-MRCAs in a window close to 50 kya (out-of-Africa migration), and an additional bottleneck for non-African populations at about 10 kya, interpreted as reflecting cultural changes increasing the variance in male reproductive success (i.e. increased social stratification) in the Neolithic.

Family tree

The revised root of the y-chromosome family tree by Cruciani et al. 2011 compared with the family tree from Karafet et al. 2008. It is now known that there is a haplogroup (A00) outside of this scheme. The group designated A1b here is now called A0, and "A1b" is now used for what is here called A2-T.

Initial sequencing (Karafet et al., 2008) of the human Y chromosome suggested that two most basal Y-chromosome lineages were Haplogroup A and Haplogroup BT. Haplogroup A is found at low frequencies in parts of Africa, but is common among certain hunter-gatherer groups. Haplogroup BT lineages represent the majority of African Y-chromosome lineages and virtually all non-African lineages. Y-chromosomal Adam was represented as the root of these two lineages. Haplogroup A and Haplogroup BT represented the lineages of Y-chromosomal Adam himself and of one of his sons, who had a new SNP.

Cruciani et al. 2011, determined that the deepest split in the Y-chromosome tree was found between two previously reported subclades of Haplogroup A, rather than between Haplogroup A and Haplogroup BT. Later, group A00 was found, outside of the previously known tree. The rearrangement of the Y-chromosome family tree implies that lineages classified as Haplogroup A do not necessarily form a monophyletic clade. Haplogroup A therefore refers to a collection of lineages that do not possess the markers that define Haplogroup BT, though Haplogroup A includes the most distantly related Y chromosomes.

The M91 and P97 mutations distinguish Haplogroup A from Haplogroup BT. Within Haplogroup A chromosomes, the M91 marker consists of a stretch of 8 T nucleobase units. In Haplogroup BT and chimpanzee chromosomes, this marker consists of 9 T nucleobase units. This pattern suggested that the 9T stretch of Haplogroup BT was the ancestral version and that Haplogroup A was formed by the deletion of one nucleobase. Haplogroups A1b and A1a were considered subclades of Haplogroup A as they both possessed the M91 with 8Ts.

But according to Cruciani et al. 2011, the region surrounding the M91 marker is a mutational hotspot prone to recurrent mutations. It is therefore possible that the 8T stretch of Haplogroup A may be the ancestral state of M91 and the 9T of Haplogroup BT may be the derived state that arose by an insertion of 1T. This would explain why subclades A1b and A1a-T, the deepest branches of Haplogroup A, both possess the same version of M91 with 8Ts. Furthermore, Cruciani et al. 2011 determined that the P97 marker, which is also used to identify Haplogroup A, possessed the ancestral state in Haplogroup A but the derived state in Haplogroup BT.

Likely geographic origin

Further information: Haplogroup A (Y-DNA)

As current estimates on TMRCA converge with estimates for the age of anatomically modern humans and well predate the Out of Africa migration, geographical origin hypotheses continue to be limited to the African continent.

According to Cruciani et al. 2011, the most basal lineages have been detected in West, Northwest and Central Africa, suggesting plausibility for the Y-MRCA living in the general region of "Central-Northwest Africa".

Scozzari et al. (2012) agreed with a plausible placement in "the north-western quadrant of the African continent" for the emergence of the A1b haplogroup.  The 2013 report of haplogroup A00 found among the Mbo people of western present-day Cameroon is also compatible with this picture.

The revision of Y-chromosomal phylogeny since 2011 has affected estimates for the likely geographical origin of Y-MRCA as well as estimates on time depth. By the same reasoning, future discovery of presently-unknown archaic haplogroups in living people would again lead to such revisions. In particular, the possible presence of between 1% and 4% Neanderthal-derived DNA in Eurasian genomes implies that the (unlikely) event of a discovery of a single living Eurasian male exhibiting a Neanderthal patrilineal line would immediately push back T-MRCA ("time to MRCA") to at least twice its current estimate. However, the discovery of a Neanderthal Y-chromosome by Mendez et al. suggests the extinction of Neanderthal patrilineages, as the lineage inferred from the Neanderthal sequence is outside of the range of contemporary human genetic variation. Questions of geographical origin would become part of the debate on Neanderthal evolution from Homo erectus.