Autoimmune disease in women

From Wikipedia, the free encyclopedia

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

Autoimmunity refers to a pathological immune response of the body's immune system against itself. Autoimmune disease is widely recognized to be significantly more common in women than in men, and often presents differently between the sexes. In addition to gender, race and ethnicity can also play a role in prevalence rates. The reasons for these disparities are still under investigation, but may in part involve the presence of an additional X chromosome in women (given that several genes on the X chromosome are associated with immune system development), as well as the higher presence of female sex hormones such as estrogen (which increases immune system response). The risk, incidence, and character of autoimmune disease in women may also be associated with female-specific physiological changes, such as hormonal shifts during menses, pregnancy, and menopause.

Common autoimmune symptoms experienced by both sexes include rashes, fevers, fatigue, and joint pain. Symptoms which are specific to women include irregular menses, pelvic pain, or vaginal dryness, depending on the given disease. Some diseases such as Graves' disease, rheumatoid arthritis, and multiple sclerosis may improve during pregnancy, whereas others such as lupus may worsen.

Currently, it is not possible to cure autoimmune disease, but many treatments are available. Treatment of autoimmune disease can be broadly classified into anti-inflammatory, immunosuppressive, and palliative – i.e., correcting a functional disturbance related to the condition. Some medications used to treat autoimmune diseases might not be safe to use during pregnancy.

Specific roles of discrimination and disparities may impact women with autoimmune diseases in the categories of race and ethnicity, gaps in research, in workplaces, and in healthcare coverage and treatment. Accommodations can be put instituted in workplaces to balance disease profiles and working conditions.

Common diseases

Autoimmune Disease Cases by Sex

Disease	Ratio of female:male cases
Addison's disease	1.5:1
Ankylosing spondylitis	1:3 – 1:4
anti-GBM disease (Goodpasture syndrome)	1:2 – 1:9
Antiphospholipid syndrome	3.5:1
Autoimmune hepatitis	3:1
Behçet's disease	1:5 – 2:1
Celiac disease	1.5:1 – 2:1
Crohn's disease	1:1 (though F>M after age 25)
Dermatomyositis	2:1 – 3:1
Diabetes type 1	1:1.8
Giant cell arteritis	3:1 – 4:1
Graves' disease	5:1
Hashimoto's thyroiditis	4:1 – 9:1
Multiple sclerosis	2:1 – 3:1
Myelin Oligodendrocyte Glycoprotein Antibody-Associated Disease (MOGAD)	1:1
Myasthenia gravis	3:1 (below 40 years of age)
Neuromyelitis Optica (NMOSD)	9:1
Pemphigus vulgaris	2:1
Polymyositis	2:1
Primary biliary cholangitis	9:1
Primary sclerosing cholangitis	1:2
Rheumatoid arthritis	2:1
Sjögren's disease	9:1
Systemic lupus erythematosus	9:1
Systemic sclerosis (scleroderma)	3:1 – 9:1
Takayasu's arteritis	9:1
Ulcerative colitis	1:1 (though M>F after age 45)

There are over 100 autoimmune conditions described, of which the majority are more prevalent in women than in men. Approximately 80% of all patients with autoimmune disease are women.

Autoimmune diseases which overwhelmingly affect women include those which affect the thyroid gland (Hashimoto's thyroiditis, Graves' disease), rheumatic diseases (systemic lupus erythematosus, rheumatoid arthritis, scleroderma, and Sjögren's disease), hepatobiliary diseases (primary biliary cholangitis, autoimmune hepatitis), and neurological diseases (myasthenia gravis, neuromyelitis optica spectrum disorders (NMOSD), and multiple sclerosis). For men who may develop these conditions, epidemiological and symptomological differences may still exist. For example, when multiple sclerosis and rheumatoid arthritis do occur in men, they tend to develop later in life for men (around age 30–40) than for women, when incidence rises after puberty.

Some autoimmune diseases affect both sexes at roughly equal rates, or have only a slight female predominance. These conditions include inflammatory bowel disease (ulcerative colitis, Crohn's disease), immune thrombocytopenic purpura (ITP), and MOG antibody disease, among others. Although the lifetime incidence of these diseases may be similar, there may still exist a difference in disease onset, course, complications, and prognosis, which vary based on sex. For example, men are more likely to develop Crohn's disease in the upper GI tract compared to women. Males and females are equally as likely to be affected by Crohn's disease until around age 25, when women become overrepresented as Crohn's disease patients. Women and men are equally likely to develop ulcerative colitis until age 45, after which this shifts to a significant male predominance.

Very few autoimmune diseases are thought to be more common in men than in women. Examples of these may include ankylosing spondylitis, primary sclerosing cholangitis, type 1 diabetes, and certain vasculitides including anti-GBM disease (Goodpasture syndrome) and Behçet's disease (though whether this represents an autoimmune disease vs autoinflammatory disease remains unclear.) On closer inspection, some diseases initially thought to be overrepresented in men have trended towards sex neutrality over time. For example, early studies of ankylosing spondylitis reported a ratio of 10:1 male to female patients, but more recent reports have indicated this is closer to 3:1. This may reflect a true increased incidence in women over time, or may be due to improvements in diagnostic testing.

Additionally, sex ratios of affected patients can vary widely between geographic regions. For instance, Crohn's disease is slightly more common in women in Western countries, whereas it is slightly more common in men in Asian countries. Behçet's disease is more common in males in regions along the historic Silk Road, but is more common in women in the United States. This suggests that the risks of developing autoimmune disease are multifactorial, and may vary based on race and environment as well as sex.

Race and ethnicity

Race and ethnicity also has data affecting prevalence rates for women with autoimmune diseases. For example, in comparison to white females, Lupus is more prevalent predominately black, but also native American, Asian, and Hispanic females. For Native American women, autoimmune hyperparathyroidism is more prevalent. In addition, among Caucasian women, celiac disease (or gluten intolerance) is more prevalent than in other races or genders.

Signs and symptoms

Autoimmune diseases can result in systemic or localized symptoms, depending on the given disease. Typical systemic symptoms include fevers, fatigue, muscle aches, joint pain, and rashes; these can be seen in diseases such as lupus or rheumatoid arthritis. Other autoimmune diseases have localized effects on specific organs or tissue types. For instance, alopecia areata presents with patchy baldness due to autoimmune destruction of hair follicles, whereas multiple sclerosis presents with neurological symptoms due to autoimmune demyelination of the central nervous system.

Both systemic and localized disease can present with symptoms that are exclusive to women. Women with Sjögren's disease (an autoimmune disease characterized by destruction and inflammation of the salivary and lacrimal glands) are 2–3 times more likely to report vaginal dryness than other postmenopausal women.

Causes

The causes of autoimmunity remain the subject of extensive research and include genetic as well as environmental factors. However, the clear overrepresentation of women as persons with autoimmune disease suggests that sex-specific factors are highly instrumental in the development of these conditions. Posited reasons for this disparity include the differential effects of sex hormones (especially estrogen) on immune response, X-chromosome inactivation, changes associated with pregnancy, and evolutionary pressures that affect the sexes differently. Due to biological development, many of these elements are inextricably linked, and it can be difficult to isolate the individual effects of each factor.

X chromosome inactivation

See also: Lyonization

Many genes involved in the immune response reside on the X chromosome, of which most women have two copies, whereas men typically only have one. During cell division in embryological development, one of the two X chromosomes is inactivated at random, in a process called lyonization. This ensures that the expression of X chromosome genes is randomly suppressed on one of the two copies in females to compensate for the extra copy of these genes. Incomplete suppression of the extra copies of these genes may lead to overexpression of some genes involved in the immune response, resulting in a more robust immune response and an increased risk of developing autoimmune diseases.

Additional support for this hypothesis can be illustrated by the higher rates of autoimmune disease in men with Klinefelter syndrome (47,XXY). Like women, males with Klinefelter syndrome also have two copies of the X chromosome, which may predispose them to increased risk of autoimmune disease through the same mechanism. This risk is highest in autoimmune diseases which are female-predominant (e.g., Addison's disease, multiple sclerosis, Sjögren's disease). With the exception of Type 1 diabetes, which affects both sexes at roughly equal rates, Klinefelter syndrome was not correlated with increased risk of autoimmune diseases which occur in males with greater or equal frequency (e.g., ankylosing spondylitis, psoriasis.)

Despite having only one copy of the X chromosome, women with Turner syndrome (45,XO) are still twice as likely as the general female population to develop autoimmune diseases. Interestingly, the autoimmune diseases for which Turner syndrome patients are at greater risk include inflammatory bowel disease, type 1 diabetes, alopecia areata, and several other autoimmune disorders, which tend to affect the sexes at roughly equal rates. This suggests that the development of autoimmune disease is not solely mediated by differential expression of genes on the X chromosome.

Sex hormones

Sex hormones are instrumental in nearly every aspect of human biology, including the development and response of the adaptive immune system. Sex hormones such as estrogen, progesterone, and testosterone are all present in healthy men and women, albeit at different levels. Estrogen and progesterone are considered primary female sex hormones, while testosterone is the primary male sex hormone. Broadly speaking, estrogen is understood to be immune-activating, while testosterone is considered to be immune-suppressing. The ideal immune system response must be alert enough to recognize and destroy foreign antigens, while also being selective enough to avoid attacking the self. There exists a necessary trade-off between immune system hyperactivity (autoimmunity) versus hypoactivity (immune deficiency). Since men and women have different levels of these sex hormones, they necessarily incur unequal risk for developing these conditions. Very broadly speaking, men are more predisposed to infectious disease, but are less likely to develop autoimmune disease. Women, conversely, are at higher risk for developing autoimmune disease, but are more protected from infectious disease than men. Women have a greater number of circulating antibodies than do men, which has implications for their development of autoimmune disease, as well as their increased resistance to infectious disease.

Estrogen

Estrogen has significant effects on the response of the adaptive immune system. Higher levels of estrogen are correlated with higher levels of circulating antibodies, which are responsible for mounting an immune response. In addition to short-term changes, the immune system may also be influenced by longer-term changes, such as total lifetime exposure. The course of disease may also be related to hormonal fluctuations, especially those of puberty, pregnancy, and menopause.

Testosterone

The immunocompetence handicap hypothesis proposes that testosterone may have utility as a secondary sexual characteristic that signals fitness to prospective mates. As males have higher levels of testosterone, which suppresses immune system activity, signaling fitness despite this handicap is a demonstration of mate quality despite this handicap. Additional proof-of-concept can be demonstrated through testosterone supplementation. Men with Klinefelter syndrome (47,XXY) naturally make very little testosterone; androgen supplementation has been shown to decrease serum levels of all immunoglobulins in these men.

Pregnancy

Pregnancy has both short- and long-term effects on the immune system, and these changes may persist even after the completion of pregnancy. These effects on the course of autoimmune diseases vary widely and are dependent on the specific disease, as well as the individual patient. Conditions such as rheumatoid arthritis often improve throughout pregnancy, especially in the second and third trimesters; however, women often relapse within three months of giving birth. Other conditions, such as lupus, often become much worse throughout pregnancy.

During pregnancy, the hormone estrogen spikes; additionally, hormonal fluctuations may continue long after childbirth. These changes could trigger, improve or even worsen an autoimmune disease. In addition to estrogen, other hormones like progesterone and prolactin may trigger these illnesses.

The mother's immune system tends to be suppressed during pregnancy to prevent fetal rejection from foreign antibodies in the fetus. As stated before, pregnancy causes an increase in estrogen in the female body. The increase of this hormone weakens the functioning of immune cells, thus debilitating the mother's immune system. In addition, fetal cells may continue to circulate in the mother's body for years after childbirth, making it a possible trigger for autoimmune disease.

Diagnosis

Autoantibodies with commonly-associated autoimmune diseases

Autoantibody	Condition
ANA*("anti-nuclear antibody")	Lupus
AHA ("anti-histone antibody")	Drug-induced lupus
ds-DNA ("anti-double-stranded DNA antibody")	Systemic lupus erythematosus with renal involvement
SMA ("anti-smooth muscle antibody")	Autoimmune Hepatitis
AMA ("anti-mitochondrial antibody")	Primary Biliary cholangitis
ACA ("anti-centromere antibody")	Scleroderma (CREST)
SS-A/Ro Ab ("anti-Sjögren's syndrome A"/"anti-Ro" antibody)	Sjögren's disease
CCP ("anti-cyclic citrullinated peptide")	Rheumatoid Arthritis
RF (rheumatoid factor)	Rheumatoid Arthritis
Jo ("anti-Jo antibody")	Polymyositis
anti-Scl-70 ("anti-topoisomerase I antibody")	Systemic Scleroderma

Diagnosis of autoimmune disease is based upon clinical and laboratory evidence. To diagnose autoimmune disease, typical symptoms of a given disorder must be present, along with laboratory evidence of autoantibodies. Autoantibodies develop throughout the course of autoimmune disease, as the immune system mistakenly forms specific antibodies to its own tissues, resulting in inflammation. The presence of autoantibodies alone is not sufficient for diagnosis, as autoantibodies may arise for a variety of other reasons, including malignancy, infection, or injury, and may be present even in completely healthy persons. However, it is possible for persons to have detectable autoantibody levels before clinically developing autoimmune disease; this state may be characterized as pre-autoimmunity. Additionally, it is possible to display clinical signs of autoimmune disease before autoantibody levels are detectable. Most autoantibody assays are more sensitive than they are specific; that is, a negative autoantibody test is better at excluding a given disease than a positive autoantibody test is at diagnosing a disease.

Generally, autoantibody results are reported in the form of titers, with higher titers (e.g., 1:160) indicating greater autoantibody concentration than lower titers (e.g., 1:8). Different autoantibody assays will have different criteria for determining whether a given test is positive, negative, or indeterminate. Other laboratories ordered in the workup of autoimmune disease may include a white blood cell count (WBC), CRP (C-reactive protein), ESR (erythrocyte sedimentation rate), and C3/C4 (complement levels), among others.

Additional circumstantial evidence to indicate a likely autoimmune disease includes family history and clustering of autoimmune diseases within a given family, presence of HLA haplotypes associated with a given disease, sex bias, and proof-of-concept through response to immunosuppressive therapy.

Treatment

See also: Autoimmune disease § Treatment

See also: Pregnancy category

Currently, it is not possible to cure any autoimmune disease. However, treatments exist that can improve the course of a given disease and/or result in long periods of remission. Pharmacological treatment of autoimmune disease can be broadly classified into anti-inflammatory, immunosuppressive, and palliative – e.g., correcting a functional disturbance related to the condition. The overall goals of such treatment are to limit the severity of flare-ups of disease, as well as to limit the total number of flares – that is, to extend periods of disease remission.

Anti-inflammatory

Nonsteroidal anti-inflammatory drugs (NSAIDs) are commonly used to reduce inflammation associated with flares of autoimmune illness. NSAIDs work by inhibiting COX-1 and COX-2 enzymes, which are responsible for generating prostaglandins which cause inflammation. They additionally may inhibit chemotaxis, stop neutrophil aggregation, and decrease levels of pro-inflammatory cytokines. They are not considered immunosuppressive agents, as they do not directly target immune cells. Examples of NSAIDs include ibuprofen, naproxen, and diclofenac. These drugs are not recommended past the 20th week of pregnancy, as they may have adverse effects on the development of the fetal circulatory system and kidneys.

Corticosteroids

Corticosteroids also have both anti-inflammatory and immunosuppressive effects,^[59] and are used widely in the treatment of autoimmune disease. They work through promoting the synthesis of multiple proteins such as lipocortin-1 and annexin A1, which stop the downstream production of prostaglandins and leukotrienes which promote inflammation. Examples of corticosteroids used in autoimmune disease include prednisone and methylprednisolone. There are no robust randomized controlled studies in humans regarding the safety of corticosteroid use in pregnancy. Corticosteroid use may be associated with cleft palate formation in the 1st trimester, but the data on this is limited. There is little evidence to suggest that maternal corticosteroid use is associated with early delivery, low birth weight, or preeclampsia. Prednisone and methylprednisolone have been classed as pregnancy category C, in that they should only be used if the maternal benefits outweigh potential risks to the fetus.^[60]

Immunosuppressive

Optimal treatment of autoimmune disease addition to quelling the generalized inflammation which may occur with autoimmune disease, treatment is also focused on specifically targeting the adaptive immune system. The goal of direct immunosuppression is to treat flares as well as extend the period of remission between episodes. Immunosuppressive drugs are categorized into DMARDs (disease-modifying anti-rheumatic drugs), as well as

DMARDs (Disease-Modifying Anti-Rheumatic Drugs)

DMARDs can be further classified into conventional-synthetic, targeted-synthetic, and biologic agents.

Palliative

Some autoimmune diseases with targeted effects on endocrine organs can result in an inability to produce hormones necessary to maintain normal physiology. Palliative treatment of autoimmune disease involves treating the secondary condition by replacing vital hormones that are no longer being produced. Examples of this include the treatment of type-1 diabetes with exogenous insulin. Though this does not cure the primary autoimmune disease, it effectively treats the lack of hormone caused by it.

Non-pharmacological

Non-pharmacological treatments are effective in treating autoimmune disease and contribute to a sense of well-being. Women can:

• Eat healthy, well-balanced meals. A healthy diet limits saturated fat, trans fat, cholesterol, salt, and added sugars. People may alleviate symptoms of inflammation by following the Autoimmune Protocol Diet, which focuses on eliminating food that may trigger inflammation. Those with autoimmune diseases should focus on consuming foods that are very fresh and nutritious.
• Engage in regular physical activity without overdoing it. Patients should speak with a clinician about what types of physical activity are appropriate. A gradual and gentle exercise program often works well for people with long-lasting muscle and joint pain. For example, yoga or tai chi may be helpful.
• Get enough rest. Rest allows body tissues and joints the time they need to repair. Sleeping is a great way to maintain the health of the mind and body. Lack of sleep, along with elevated stress levels, may cause symptoms to worsen. Without proper rest, the body's immune defense remains inadequate. Many people need at least seven to nine hours of sleep each day to feel well-rested.
• Reduce stress. Stress and anxiety can trigger symptoms to flare up in some autoimmune diseases. Simplifying daily stressors will help alleviate symptoms and contribute to a sense of well-being. Meditation, self-hypnosis, and guided imagery may be effective in reducing stress, pain, and boosting people's ability to cope with other effects of autoimmune diseases. Instructional materials can guide people in learning these activities. Some include self-help books, audio sources, tapes, or consulting with an instructor. Joining a support group or talking with a counselor might also help manage stress and cope with the disease. As women are more likely to experience certain kinds stressors, such as in caregiver roles, or in balancing caregiver roles with workplace roles, they may be exposed to epigenetic presentation risks; thus, contribution to looking at each women's different roles and implementing stressor oriented strategies accordingly can aid in management.

Complementary

Some complementary treatments may be effective and include:

• Listening to music
• Taking time to relax in a comfortable position
• Using imagery throughout the day
• Imagining confronting the pain and watching it be destroyed.
• Journaling and daily affirmations
• Traditional herbal medicine

During pregnancy

Concerns about fertility and pregnancy are present in women with autoimmune diseases. Talking with a healthcare provider before becoming pregnant is recommended. They may suggest waiting until the disease is in remission or suggest a change in medication before becoming pregnant. There are endocrinologists that specialize in treating women with high-risk pregnancies.

Some women with autoimmune diseases may have problems getting pregnant. This can happen for many reasons, such as medication types or even disease types. Tests can tell if fertility problems are caused by an autoimmune disease or an unrelated reason. Fertility treatments can help some women with autoimmune disease become pregnant.

Changes in the severity of the disease seem to vary depending on the type of disease. There is an observable trend in pregnant women with rheumatoid arthritis, where the condition seems to improve during pregnancy. Differently, expecting mothers with systemic lupus erythematosus (SLE) may be more likely to have worsened symptoms through pregnancy; however, this is difficult to predict.

Certain medications can hinder women's ability to get pregnant, such as cyclophosphamide or corticosteroids. For this reason, it may be helpful for women with autoimmune diseases to seek treatment when conceiving.

Discrimination and disparities

Race and ethnicity

Varying forms of discrimination have been reported by women with autoimmune diseases of differing races and ethnicities. Black women diagnosed with lupus, when in healthcare settings, have reported the following conditions when interacting with healthcare providers: low compassion, low respect, racial discrimination, ethnic discrimination, hurried communication, distracted discrimination, as well as fears around being stereotyped, and not included in medical decisions. In a similar survey, fears around being given poor medical care, being exploited in research, and loosing legal status where recorded by Hispanic and Latinx men and women with multiple sclerosis. Women of color with autoimmune disease also report more interactions with providers around dismissal of symptoms.

Health outcomes can be impacted by the intersection of race, gender, and autoimmune diseases. Studies on women of color found heightened autoimmune disease activity after experiencing discrimination from healthcare providers.

In the area of treatment, factors related to race and ethnicity can also be noted. Medical care that takes into account research, and training in reducing differing discriminations, and building sensitivity to cultures, is able to account for the population at hand and recognize treatment factors that may be beneficial to the individual. This includes the mentioned and recorded fears, and also factors important to patients. For example, Caribbean black women diagnosed with multiple sclerosis are more likely to use faith related logic in their treatments and diagnosis than the general population.

Research gaps

In autoimmune disease research, there exist gaps for gender, and intersectional race and ethnicities. Historical, areas of research, including for medical conditions, have found their sample sizes with white males. In 2022, only 32 of 2305 federal funded research titles included the words "Sex, gender, female, maternal, or variations of women, pregnancy, or lactating", though women are disproportionately affected and diagnosed with autoimmune diseases. In 2024, a new race category that separated Arab individuals from Caucasians was added in federal research. Arabians have been shown to have higher rates of autoantibodies prevalent in autoimmune diseases, and due to this only recent separation lack research. In all, more gender focused research can be conducted and combined with race and ethnicity data to produce further research in identifying prevalences, gaps, treatment, and diagnosis, for women across a spectrum.

Workplace

The impact of workplace burden, stigma, discrimination have been studied in workplaces across various autoimmune diseases. Higher burden has been recorded in autoimmune conditions such as irritable bowel disease Inflammatory bowel disease (IBD), which includes higher burdens in the workplace due to needing more sick leave, disability support, and in some cases periods (such as with flair ups) unemployment. Women autoimmune diseases also face similar burdens as disability, even if temporary, can occur and limit working capacity and increase cognitive impairment, pain, fatigue, illness, as well as mental symptoms such as anxiety and depression.

Stigma can compound the stress of an autoimmune disease, and can be more pronounced when disability is more evident, and when the disease is more progressive. Fear of stigmatization, as a factor of stigma, can impact multiple factors in a workers life, such as preventing them from requesting accommodations, limiting them from bringing accommodations to work, fearing coworkers negatively changing perspectives, shift beliefs to thinking employers will choose other candidates for a position, and even install ideas that they may be fired for their condition. All of these factors in the fear of stigmatization have been seen to limit those with autoimmune diseases from seeking work, disclosing conditions, and have lead to leaving positions in anticipatory fear.

Improving workplace perceptions can improve conditions for those with autoimmune diseases. For some examples, stigma reducing workplace interventions, improved education about conditions, positive behaviors from coworkers and leaders, legal protections, and safety around trusting employees, can improve a workers feelings of safety and acceptance in the workplace. As many autoimmune conditions can be termed invisible illnesses, and have varied and fluctuating presentations impacting workers in different ways, increasing awareness about conditions and the physical and mental toll they take, not just visually, can improve employer and coworker perceptions.

Healthcare coverage and settings

From a financial perspective, women with autoimmune diseases differ from men. Compared to men, data shows out of pocket costs for healthcare are reported to be 15 billion dollars more women, employee sponsored insurance cover over a billion dollars less for women, and when insured over 30% of women reported healthcare aid to be insufficient for medical costs.  Not having insurance and/or low income can create barriers receiving treatments, and in turn create long term consequences as well impact daily quality of living for women.

In healthcare settings, 41% of rheumatologists are women and under 10% are a racial minority, creating contrast to the 80% of the women population treated by the specialty. Many women who are diagnosed with autoimmune disorders take years and multiple doctors to be diagnosed, which can be impacted by the nature of autoimmune diseases and provider interactions. Improved provider care interactions include listening and education when treating women to look for signs and symptoms. Providers can take measures of education in order to relate to their patients and the unique challenges they face in gender and ethnicity, improving treatment outcomes, progression, and feelings of comfort and safety.

Accommodations

Workplace accommodations

Autoimmune diseases, due to their ability to alter quality of life including day to day tasks- such as in the workplace- can require accommodations. Accommodations, though, are diverse in the same way presentations of autoimmune diseases are diverse. In the workplace, accommodations can include a spectrum from policies for invisible illnesses to mobility devices for progressive illnesses.

A list of possible accommodations includes:

• Telecommuting options.
• Flexible hours, starting times, and amount of workdays.
• Breaks when needed, such as in the case of IBD.
• Temperature and light control, such as for Lupus.
• Modifying tasks during flare ups, such as reducing repetitive movements in joint based autoimmune conditions.
• Pregnancy and childbirth accommodations which may trigger flare ups in conditions such as Lupus.
• Working with a vocational rehabilitation counselor

Cosmic string

From Wikipedia, the free encyclopedia

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

Cosmic strings are hypothetical 1-dimensional topological defects which may have formed during a symmetry-breaking phase transition in the early universe when the topology of the vacuum manifold associated to this symmetry breaking was not simply connected.

In less formal terms, they are hypothetical long, thin defects in the fabric of space. They might have formed in the early universe during a process where certain symmetries were broken. Their existence was first contemplated by the theoretical physicist Tom Kibble in the 1970s.

The formation of cosmic strings is somewhat analogous to the imperfections that form between crystal grains in solidifying liquids, or the cracks that form when water freezes into ice. The phase transitions leading to the production of cosmic strings are likely to have occurred during the earliest moments of the universe's evolution, just after cosmological inflation, and are a fairly generic prediction in both quantum field theory and string theory models of the early universe.

Theories containing cosmic strings

The prototypical example of a field theory with cosmic strings is the Abelian Higgs model. The quantum field theory and string theory cosmic strings are expected to have many properties in common, but more research is needed to determine the precise distinguishing features. The F-strings for instance are fully quantum-mechanical and do not have a classical definition, whereas the field theory cosmic strings are almost exclusively treated classically.

In superstring theory, the role of cosmic strings can be played by the fundamental strings (or F-strings) themselves that define the theory perturbatively, by D-strings which are related to the F-strings by weak-strong or so called S-duality, or higher-dimensional D-, NS- or M-branes that are partially wrapped on compact cycles associated to extra spacetime dimensions so that only one non-compact dimension remains.

Dimensions

Cosmic strings, if they exist, would be extremely thin topological defects with diameters of the same order of magnitude as that of a proton, i.e. ~1 fm, or smaller. Given that this scale is much smaller than any cosmological scale, these strings are often studied in the zero-width, or Nambu–Goto approximation. Under this assumption, strings behave as one-dimensional objects and obey the Nambu–Goto action, which is classically equivalent to the Polyakov action that defines the bosonic sector of superstring theory.

In field theory, the string width is set by the scale of the symmetry-breaking phase transition. In string theory, the string width is set (in the simplest cases) by the fundamental string scale, warp factors (associated to the spacetime curvature of an internal six-dimensional spacetime manifold) and/or the size of internal compact dimensions. (In string theory, the universe is either 10- or 11-dimensional, depending on the strength of interactions and the curvature of spacetime.)

Gravitation

A string is a geometrical deviation from Euclidean geometry in spacetime characterized by an angular deficit: a circle around the outside of a string would comprise a total angle less than 360°. From the general theory of relativity such a geometrical defect must be in tension, and would be manifested by mass. Even though cosmic strings are thought to be extremely thin, they would have immense density, and so would represent significant gravitational wave sources. A cosmic string about a kilometer in length may be more massive than the Earth.

However general relativity predicts that the gravitational potential of a straight string vanishes: there is no gravitational force on static surrounding matter. The only gravitational effect of a straight cosmic string is a relative deflection of matter (or light) passing the string on opposite sides (a purely topological effect). A closed cosmic string gravitates in a more conventional way.

During the expansion of the universe, cosmic strings would form a network of loops, and in the past it was thought that their gravity could have been responsible for the original clumping of matter into galactic superclusters. It is now calculated that their contribution to the structure formation in the universe is less than 10%.

Negative mass cosmic string

The standard model of a cosmic string is a geometrical structure with an angle deficit, which thus is in tension and hence has positive mass. In 1995, Visser et al. proposed that cosmic strings could theoretically also exist with angle excesses, and thus negative tension and hence negative mass. The stability of such exotic matter strings is problematic; however, they suggested that if a negative mass string were to be wrapped around a wormhole in the early universe, such a wormhole could be stabilized sufficiently to exist in the present day.

Super-critical cosmic string

The exterior geometry of a (straight) cosmic string can be visualized in an embedding diagram as follows: Focusing on the two-dimensional surface perpendicular to the string, its geometry is that of a cone which is obtained by cutting out a wedge of angle δ and gluing together the edges. The angular deficit δ is linearly related to the string tension (= mass per unit length), i.e. the larger the tension, the steeper the cone. Therefore, δ reaches 2π for a certain critical value of the tension, and the cone degenerates to a cylinder. (In visualizing this setup one has to think of a string with a finite thickness.) For even larger, "super-critical" values, δ exceeds 2π and the (two-dimensional) exterior geometry closes up (it becomes compact), ending in a conical singularity.

However, this static geometry is unstable in the super-critical case (unlike for sub-critical tensions): Small perturbations lead to a dynamical spacetime which expands in axial direction at a constant rate. The 2D exterior is still compact, but the conical singularity can be avoided, and the embedding picture is that of a growing cigar. For even larger tensions (exceeding the critical value by approximately a factor of 1.6), the string cannot be stabilized in radial direction anymore.

Realistic cosmic strings are expected to have tensions around 6 orders of magnitude below the critical value, and are thus always sub-critical. However, the inflating cosmic string solutions might be relevant in the context of brane cosmology, where the string is promoted to a 3-brane (corresponding to our universe) in a six-dimensional bulk.

Observational evidence

It was once thought that the gravitational influence of cosmic strings might contribute to the large-scale clumping of matter in the universe, but all that is known today through galaxy surveys and precision measurements of the cosmic microwave background (CMB) fits an evolution out of random, gaussian fluctuations. These precise observations therefore tend to rule out a significant role for cosmic strings and currently it is known that the contribution of cosmic strings to the CMB cannot be more than 10%.

The violent oscillations of cosmic strings generically lead to the formation of cusps and kinks. These in turn cause parts of the string to pinch off into isolated loops. These loops have a finite lifespan and decay (primarily) via gravitational radiation. This radiation which leads to the strongest signal from cosmic strings may in turn be detectable in gravitational wave observatories. An important open question is to what extent do the pinched off loops backreact or change the initial state of the emitting cosmic string—such backreaction effects are almost always neglected in computations and are known to be important, even for order of magnitude estimates.

Gravitational lensing of a galaxy by a straight section of a cosmic string would produce two identical, undistorted images of the galaxy. In 2003 a group led by Mikhail Sazhin reported the accidental discovery of two seemingly identical galaxies very close together in the sky, leading to speculation that a cosmic string had been found. However, observations by the Hubble Space Telescope in January 2005 showed them to be a pair of similar galaxies, not two images of the same galaxy. A cosmic string would produce a similar duplicate image of fluctuations in the cosmic microwave background, which it was thought might have been detectable by the Planck Surveyor mission. However, a 2013 analysis of data from the Planck mission failed to find any evidence of cosmic strings.

A piece of evidence supporting cosmic string theory is a phenomenon noticed in observations of the "double quasar" called Q0957+561A,B. Originally discovered by Dennis Walsh, Bob Carswell, and Ray Weymann in 1979, the double image of this quasar is caused by a galaxy positioned between it and the Earth. The gravitational lens effect of this intermediate galaxy bends the quasar's light so that it follows two paths of different lengths to Earth. The result is that we see two images of the same quasar, one arriving a short time after the other (about 417.1 days later). However, a team of astronomers at the Harvard-Smithsonian Center for Astrophysics led by Rudolph Schild studied the quasar and found that during the period between September 1994 and July 1995 the two images appeared to have no time delay; changes in the brightness of the two images occurred simultaneously on four separate occasions. Schild and his team believe that the only explanation for this observation is that a cosmic string passed between the Earth and the quasar during that time period traveling at very high speed and oscillating with a period of about 100 days.

Until 2023 the most sensitive bounds on cosmic string parameters came from the non-detection of gravitational waves by pulsar timing array data. The first detection of gravitational waves with pulsar timing array was confirmed in 2023. The earthbound Laser Interferometer Gravitational-Wave Observatory (LIGO) and especially the space-based gravitational wave detector Laser Interferometer Space Antenna (LISA) will search for gravitational waves and are likely to be sensitive enough to detect signals from cosmic strings, provided the relevant cosmic string tensions are not too small.

String theory and cosmic strings

During the early days of string theory both string theorists and cosmic string theorists believed that there was no direct connection between superstrings and cosmic strings (the names were chosen independently by analogy with ordinary string). The possibility of cosmic strings being produced in the early universe was first envisioned by quantum field theorist Tom Kibble in 1976, and this sprouted the first flurry of interest in the field.

In 1985, during the first superstring revolution, Edward Witten contemplated on the possibility of fundamental superstrings having been produced in the early universe and stretched to macroscopic scales, in which case (following the nomenclature of Tom Kibble) they would then be referred to as cosmic superstrings. He concluded that had they been produced they would have either disintegrated into smaller strings before ever reaching macroscopic scales (in the case of Type I superstring theory), they would always appear as boundaries of domain walls whose tension would force the strings to collapse rather than grow to cosmic scales (in the context of heterotic superstring theory), or having a characteristic energy scale close to the Planck energy they would be produced before cosmological inflation and hence be diluted away with the expansion of the universe and not be observable.

Much has changed since these early days, primarily due to the second superstring revolution. It is now known that string theory contains, in addition to the fundamental strings which define the theory perturbatively, other one-dimensional objects, such as D-strings, and higher-dimensional objects such as D-branes, NS-branes and M-branes partially wrapped on compact internal spacetime dimensions, while being spatially extended in one non-compact dimension. The possibility of large compact dimensions and large warp factors allows strings with tension much lower than the Planck scale.

Furthermore, various dualities that have been discovered point to the conclusion that actually all these apparently different types of string are just the same object as it appears in different regions of parameter space. These new developments have largely revived interest in cosmic strings, starting in the early 2000s.

In 2002, Henry Tye and collaborators predicted the production of cosmic superstrings during the last stages of brane inflation, a string theory construction of the early universe that gives leads to an expanding universe and cosmological inflation. It was subsequently realized by string theorist Joseph Polchinski that the expanding Universe could have stretched a "fundamental" string (the sort which superstring theory considers) until it was of intergalactic size. Such a stretched string would exhibit many of the properties of the old "cosmic" string variety, making the older calculations useful again. As theorist Tom Kibble remarks, "string theory cosmologists have discovered cosmic strings lurking everywhere in the undergrowth". Older proposals for detecting cosmic strings could now be used to investigate superstring theory.

Superstrings, D-strings or the other stringy objects mentioned above stretched to intergalactic scales would radiate gravitational waves, which could be detected using experiments like LIGO and especially the space-based gravitational wave experiment LISA. They might also cause slight irregularities in the cosmic microwave background, too subtle to have been detected yet but possibly within the realm of future observability.

Note that most of these proposals depend, however, on the appropriate cosmological fundamentals (strings, branes, etc.), and no convincing experimental verification of these has been confirmed to date. Cosmic strings nevertheless provide a window into string theory. If cosmic strings are observed, which is a real possibility for a wide range of cosmological string models, this would provide the first experimental evidence of a string theory model underlying the structure of spacetime.

Cosmic string network

There are many attempts to detect the footprint of a cosmic strings network.

Potential applications

In 1986, John G. Cramer proposed that spacecraft equipped with magnet coils could travel along cosmic strings, analogous to how a maglev train travels along a rail line.

Punctuated equilibrium

From Wikipedia, the free encyclopedia

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

The punctuated equilibrium model (top) consists of morphological stability followed by rare bursts of evolutionary change via rapid cladogenesis – vertical equilibrium states separated by horizontal "jump" phases. In contrast, phyletic gradualism (below), is a more gradual, continuous model of evolution – with accumulation of small incremental changes represented by slanted bars that split at branch-points, where two separate modes of life are feasible but of which, each prospers best with divergent specializations.

In evolutionary biology, punctuated equilibrium (also called punctuated equilibria) is a theory that proposes that once a species appears in the fossil record, the population will become stable, showing little evolutionary change for most of its geological history. This state of little or no morphological change is called stasis. When significant evolutionary change occurs, the theory proposes that it is generally restricted to rare and geologically rapid events of branching speciation called cladogenesis. Cladogenesis is the process by which a species splits into two distinct species, rather than one species gradually transforming into another.

Punctuated equilibrium is commonly contrasted with phyletic gradualism, the idea that evolution generally occurs uniformly by the steady and gradual transformation of whole lineages (anagenesis).

In 1972, paleontologists Niles Eldredge and Stephen Jay Gould published a landmark paper developing their theory and called it punctuated equilibria. Their paper built upon Ernst Mayr's model of geographic speciation, I. M. Lerner's theories of developmental and genetic homeostasis, and their own empirical research. Eldredge and Gould proposed that the degree of gradualism commonly attributed to Charles Darwin is virtually nonexistent in the fossil record, and that stasis dominates the history of most fossil species.

History

Punctuated equilibrium originated as a logical consequence of Ernst Mayr's concept of genetic revolutions by allopatric and especially peripatric speciation as applied to the fossil record. Although the sudden appearance of species and its relationship to speciation was proposed and identified by Mayr in 1954, historians of science generally recognize the 1972 Eldredge and Gould paper as the basis of the new paleobiological research program. Punctuated equilibrium differs from Mayr's ideas mainly in that Eldredge and Gould placed considerably greater emphasis on stasis, whereas Mayr was concerned with explaining the morphological discontinuity (or "sudden jumps") found in the fossil record. Mayr later complimented Eldredge and Gould's paper, stating that evolutionary stasis had been "unexpected by most evolutionary biologists" and that punctuated equilibrium "had a major impact on paleontology and evolutionary biology."

A year before his and Gould's 1972 paper, Niles Eldredge published a paper in the journal Evolution which suggested that gradual evolution was seldom seen in the fossil record and argued that Ernst Mayr's standard mechanism of allopatric speciation might suggest a possible resolution.

The Eldredge and Gould paper was presented at the Annual Meeting of the Geological Society of America in 1971. The symposium focused its attention on how modern microevolutionary studies could revitalize various aspects of paleontology and macroevolution. Tom Schopf, who organized that year's meeting, assigned Gould the topic of speciation. Gould recalls that "Eldredge's 1971 publication [on Paleozoic trilobites] had presented the only new and interesting ideas on the paleontological implications of the subject—so I asked Schopf if we could present the paper jointly." According to Gould "the ideas came mostly from Niles, with yours truly acting as a sounding board and eventual scribe. I coined the term punctuated equilibrium and wrote most of our 1972 paper, but Niles is the proper first author in our pairing of Eldredge and Gould." In his book Time Frames Eldredge recalls that after much discussion the pair "each wrote roughly half. Some of the parts that would seem obviously the work of one of us were actually first penned by the other—I remember for example, writing the section on Gould's snails. Other parts are harder to reconstruct. Gould edited the entire manuscript for better consistency. We sent it in, and Schopf reacted strongly against it—thus signaling the tenor of the reaction it has engendered, though for shifting reasons, down to the present day."

John Wilkins and Gareth Nelson have argued that French architect Pierre Trémaux proposed an "anticipation of the theory of punctuated equilibrium of Gould and Eldredge."

Evidence from the fossil record

Main article: Rate of evolution

The fossil record includes well documented examples of both phyletic gradualism and punctuational evolution. As such, much debate persists over the prominence of stasis in the fossil record.Before punctuated equilibrium, most evolution biologists considered stasis to be rare or unimportant.The paleontologist George Gaylord Simpson, for example, believed that phyletic gradual evolution (called horotely in his terminology) comprised 90% of evolution. More modern studies, including a meta-analysis examining 58 published studies on speciation patterns in the fossil record showed that 71% of species exhibited stasis, and 63% were associated with punctuated patterns of evolutionary change. According to Michael Benton, "it seems clear then that stasis is common, and that had not been predicted from modern genetic studies." A paramount example of evolutionary stasis is the fern Osmunda claytoniana. Based on paleontological evidence it has remained unchanged, even at the level of fossilized nuclei and chromosomes, for at least 180 million years.

Theoretical mechanisms

Punctuational change

When Eldredge and Gould published their 1972 paper, allopatric speciation was considered the "standard" model of speciation. This model was popularized by Ernst Mayr in his 1954 paper "Change of genetic environment and evolution," and his classic volume Animal Species and Evolution (1963).

Allopatric speciation suggests that species with large central populations are stabilized by their large volume and the process of gene flow. New and even beneficial mutations are diluted by the population's large size and are unable to reach fixation, due to such factors as constantly changing environments. If this is the case, then the transformation of whole lineages should be rare, as the fossil record indicates. Smaller populations on the other hand, which are isolated from the parental stock, are decoupled from the homogenizing effects of gene flow. In addition, pressure from natural selection is especially intense, as peripheral isolated populations exist at the outer edges of ecological tolerance. If most evolution happens in these rare instances of allopatric speciation then evidence of gradual evolution in the fossil record should be rare. This hypothesis was alluded to by Mayr in the closing paragraph of his 1954 paper:

Rapidly evolving peripherally isolated populations may be the place of origin of many evolutionary novelties. Their isolation and comparatively small size may explain phenomena of rapid evolution and lack of documentation in the fossil record, hitherto puzzling to the palaeontologist.

Although punctuated equilibrium generally applies to sexually reproducing organisms, some biologists have applied the model to non-sexual species like viruses, which cannot be stabilized by conventional gene flow. As time went on biologists like Gould moved away from wedding punctuated equilibrium to allopatric speciation, particularly as evidence accumulated in support of other modes of speciation. Gould, for example, was particularly attracted to Douglas Futuyma's work on the importance of reproductive isolating mechanisms.

Stasis

Many hypotheses have been proposed to explain the putative causes of stasis. Gould was initially attracted to I. Michael Lerner's theories of developmental and genetic homeostasis. However this hypothesis was rejected over time, as evidence accumulated against it. Other plausible mechanisms which have been suggested include: habitat tracking, stabilizing selection, the Stenseth-Maynard Smith stability hypothesis, constraints imposed by the nature of subdivided populations, normalizing clade selection, and koinophilia.

Evidence for stasis has also been corroborated from the genetics of sibling species, species which are morphologically indistinguishable, but whose proteins have diverged sufficiently to suggest they have been separated for millions of years. Fossil evidence of reproductively isolated extant species of sympatric Olive Shells (Amalda sp.) also confirm morphological stasis in multiple lineages over three million years.

According to Gould, "stasis may emerge as the theory's most important contribution to evolutionary science." Philosopher Kim Sterelny in clarifying the meaning of stasis adds, "In claiming that species typically undergo no further evolutionary change once speciation is complete, they are not claiming that there is no change at all between one generation and the next. Lineages do change. But the change between generations does not accumulate. Instead, over time, the species wobbles about its phenotypic mean. Jonathan Weiner's The Beak of the Finch describes this very process."

Hierarchical evolution

Punctuated equilibrium has also been cited as contributing to the hypothesis that species are Darwinian individuals, and not just classes, thereby providing a stronger framework for a hierarchical theory of evolution.

Common misconceptions

Much confusion has arisen over what proponents of punctuated equilibrium actually argued, what mechanisms they advocated, how fast the punctuations were, what taxonomic scale their theory applied to, how revolutionary their claims were intended to be, and how punctuated equilibrium related to other ideas like saltationism, quantum evolution, and mass extinction.

Saltationism

Alternative explanations for the punctuated pattern of evolution observed in the fossil record. Both macromutation and seemingly "rapid" episodes of gradual evolution could give the appearance of instantaneous change, since 10,000 years seldom registers in the geological record.

The punctuational nature of punctuated equilibrium has engendered perhaps the most confusion over Eldredge and Gould's theory. Gould's sympathetic treatment of Richard Goldschmidt, the controversial geneticist who advocated the idea of "hopeful monsters," led some biologists to conclude that Gould's punctuations were occurring in single-generation jumps. This interpretation has frequently been used by creationists to characterize the weakness of the paleontological record, and to portray contemporary evolutionary biology as advancing neo-saltationism.

In an often quoted remark, Gould stated,

"Since we proposed punctuated equilibria to explain trends, it is infuriating to be quoted again and again by creationists – whether through design or stupidity, I do not know – as admitting that the fossil record includes no transitional forms. Transitional forms are generally lacking at the species level, but they are abundant between larger groups."

Although there exist some debate over how long the punctuations last, supporters of punctuated equilibrium generally place the figure between 50,000 and 100,000 years.

Quantum evolution

Quantum evolution was a controversial hypothesis advanced by Columbia University paleontologist George Gaylord Simpson, regarded by Gould as "the greatest and most biologically astute paleontologist of the twentieth century." Simpson's conjecture was that according to the geological record, on very rare occasions evolution would proceed very rapidly to form entirely new families, orders, and classes of organisms. This hypothesis differs from punctuated equilibrium in several respects. First, punctuated equilibrium was more modest in scope, in that it was addressing evolution specifically at the species level. Simpson's idea was principally concerned with evolution at higher taxonomic groups. Second, Eldredge and Gould relied upon a different mechanism. Where Simpson relied upon a synergistic interaction between genetic drift and a shift in the adaptive fitness landscape, Eldredge and Gould relied upon ordinary speciation, particularly Ernst Mayr's concept of allopatric speciation. Lastly, and perhaps most significantly, quantum evolution took no position on the issue of stasis. Although Simpson acknowledged the existence of stasis in what he called the bradytelic mode, he considered it (along with rapid evolution) to be unimportant in the larger scope of evolution. In his Major Features of Evolution Simpson stated, "Evolutionary change is so nearly the universal rule that a state of motion is, figuratively, normal in evolving populations. The state of rest, as in bradytely, is the exception and it seems that some restraint or force must be required to maintain it." Despite such differences between the two models, earlier critiques—from such eminent commentators as Sewall Wright as well as Simpson himself—have argued that punctuated equilibrium is little more than quantum evolution relabeled.

Multiple meanings of gradualism

Punctuated equilibrium is often portrayed to oppose the concept of gradualism, when it is actually a form of gradualism. This is because even though evolutionary change appears instantaneous between geological sedimentary layers, change is still occurring incrementally, with no great change from one generation to the next. To this end, Gould later commented that "Most of our paleontological colleagues missed this insight because they had not studied evolutionary theory and either did not know about allopatric speciation or had not considered its translation to geological time. Our evolutionary colleagues also failed to grasp the implication(s), primarily because they did not think at geological scales".

Richard Dawkins dedicates a chapter in The Blind Watchmaker to correcting, in his view, the wide confusion regarding rates of change. His first point is to argue that phyletic gradualism—understood in the sense that evolution proceeds at a single uniform speed, called "constant speedism" by Dawkins—is a "caricature of Darwinism" and "does not really exist". His second argument, which follows from the first, is that once the caricature of "constant speedism" is dismissed, we are left with one logical alternative, which Dawkins terms "variable speedism". Variable speedism may also be distinguished one of two ways: "discrete variable speedism" and "continuously variable speedism". Eldredge and Gould, proposing that evolution jumps between stability and relative rapidity, are described as "discrete variable speedists", and "in this respect they are genuinely radical." They assert that evolution generally proceeds in bursts, or not at all. "Continuously variable speedists", on the other hand, advance that "evolutionary rates fluctuate continuously from very fast to very slow and stop, with all intermediates. They see no particular reason to emphasize certain speeds more than others. In particular, stasis, to them, is just an extreme case of ultra-slow evolution. To a punctuationist, there is something very special about stasis."

Criticism

See also: Species problem, Species complex, and Push of the past

Richard Dawkins regards the apparent gaps represented in the fossil record as documenting migratory events rather than evolutionary events. According to Dawkins, evolution certainly occurred but "probably gradually" elsewhere. However, the punctuational equilibrium model may still be inferred from both the observation of stasis and examples of rapid and episodic speciation events documented in the fossil record.

Dawkins also emphasizes that punctuated equilibrium has been "oversold by some journalists", but partly due to Eldredge and Gould's "later writings". Dawkins contends that the hypothesis "does not deserve a particularly large measure of publicity". It is a "minor gloss," an "interesting but minor wrinkle on the surface of neo-Darwinian theory," and "lies firmly within the neo-Darwinian synthesis".

In his book Darwin's Dangerous Idea, philosopher Daniel Dennett is especially critical of Gould's presentation of punctuated equilibrium. Dennett argues that Gould alternated between revolutionary and conservative claims, and that each time Gould made a revolutionary statement—or appeared to do so—he was criticized, and thus retreated to a traditional neo-Darwinian position. Gould responded to Dennett's claims in The New York Review of Books, and in his technical volume The Structure of Evolutionary Theory.

English professor Heidi Scott argues that Gould's talent for writing vivid prose, his use of metaphor, and his success in building a popular audience of nonspecialist readers altered the "climate of specialized scientific discourse" favorably in his promotion of punctuated equilibrium. While Gould is celebrated for the color and energy of his prose, as well as his interdisciplinary knowledge, critics such as Scott, Richard Dawkins, and Daniel Dennett have concerns that the theory has gained undeserved credence among non-scientists because of Gould's rhetorical skills. Philosopher John Lyne and biologist Henry Howe believed punctuated equilibrium's success has much more to do with the nature of the geological record than the nature of Gould's rhetoric. They state, a "re-analysis of existing fossil data has shown, to the increasing satisfaction of the paleontological community, that Eldredge and Gould were correct in identifying periods of evolutionary stasis which are interrupted by much shorter periods of evolutionary change."

Evolutionary biologist Robert Trivers accused Gould of being "something of an intellectual fraud" for using claims that were "well known from the time of Darwin" (that evolution displayed "periods of long stasis interspersed with periods of rapid change") to support distinct but more "grandiose" claims regarding species selection, despite the "rate of species turnover [having] nothing to do with the traits within species—only with the relative frequency of species showing these traits".

Some critics jokingly referred to the theory of punctuated equilibrium as "evolution by jerks", which reportedly prompted punctuationists to describe phyletic gradualism as "evolution by creeps."

Darwin's theory

The sudden appearance of most species in the geologic record and the lack of evidence of substantial gradual change in most species—from their initial appearance until their extinction—has long been noted, including by Charles Darwin, who appealed to the imperfection of the record as the favored explanation. When presenting his ideas against the prevailing influences of catastrophism and progressive creationism, which envisaged species being supernaturally created at intervals, Darwin needed to forcefully stress the gradual nature of evolution in accordance with the gradualism promoted by his friend Charles Lyell. He privately expressed concern, noting in the margin of his 1844 Essay, "Better begin with this: If species really, after catastrophes, created in showers world over, my theory false."

It is often incorrectly assumed that he insisted that the rate of change must be constant, or nearly so, but even the first edition of On the Origin of Species states that "Species of different genera and classes have not changed at the same rate, or in the same degree. In the oldest tertiary beds a few living shells may still be found in the midst of a multitude of extinct forms... The Silurian Lingula differs but little from the living species of this genus". Lingula is among the few brachiopods surviving today but also known from fossils over 500 million years old. In the fourth edition (1866) of On the Origin of Species Darwin wrote that "the periods during which species have undergone modification, though long as measured in years, have probably been short in comparison with the periods during which they retain the same form." Thus punctuationism in general is consistent with Darwin's conception of evolution.

According to early versions of punctuated equilibrium, "peripheral isolates" are considered to be of critical importance for speciation. However, Darwin wrote, "I can by no means agree ... that immigration and isolation are necessary elements. ... Although isolation is of great importance in the production of new species, on the whole I am inclined to believe that largeness of area is still more important, especially for the production of species which shall prove capable of enduring for a long period, and of spreading widely."

The importance of isolation in forming species had played a significant part in Darwin's early thinking, as shown in his Essay of 1844. But by the time he wrote the Origin he had downplayed its importance. He explained the reasons for his revised view as follows:

Throughout a great and open area, not only will there be a greater chance of favourable variations, arising from the large number of individuals of the same species there supported, but the conditions of life are much more complex from the large number of already existing species; and if some of these species become modified and improved, others will have to be improved in a corresponding degree, or they will be exterminated. Each new form, also, as soon as it has been improved, will be able to spread over the open and continuous area, and will thus come into competition with many other forms ... the new forms produced on large areas, which have already been victorious over many competitors, will be those that will spread most widely, and will give rise to the greatest number of new varieties and species. They will thus play a more important role in the changing history of the organic world.

Thus punctuated equilibrium is incongruous with some of Darwin's ideas regarding the specific mechanisms of evolution, but generally accords with Darwin's theory of evolution by natural selection.

Supplemental modes of rapid evolution

See also: Rapid modes of evolution

Recent work in developmental biology has identified dynamical and physical mechanisms of tissue morphogenesis that may underlie abrupt morphological transitions during evolution. Consequently, consideration of mechanisms of phylogenetic change that have been found in reality to be non-gradual is increasingly common in the field of evolutionary developmental biology, particularly in studies of the origin of morphological novelty. A description of such mechanisms can be found in the multi-authored volume Origination of Organismal Form (MIT Press; 2003).

Language change

For broader coverage of this topic, see Language change.

In linguistics, R. M. W. Dixon has proposed a punctuated equilibrium model for language histories, with reference particularly to the prehistory of the indigenous languages of Australia and his objections to the proposed Pama–Nyungan language family there. Although his model has raised considerable interest, it does not command majority support within linguistics.

Separately, recent work using computational phylogenetic methods claims to show that punctuational bursts play an important factor when languages split from one another, accounting for anywhere from 10 to 33% of the total divergence in vocabulary, and around 24% of divergence among cognates in the Indo-European language family.

Mythology

Punctuational evolution has been argued to explain changes in folktales and mythology over time.