PB was initially thought to occur as a result of shaving (Blaine, 1899). Bertolino, A. P., Freedberg, I. M.  (1987)  Disorders of epidermal appendages and related disorders: Hair. Hair follicles go throughcycles of growth and dormancy. Other studies further support the presence of inflammation in PB. However, most of those studies have ignored the role that the environment plays in the development of disease, and they overlook the importance of looking at the disease from an evolutionary approach. Baldness in men is related to the male hormone dihydrotestosterone, which causes old hairs on the scalp to be replaced by progressively shorter and thinner hairs in a … From Ford et al., 1996. Heart disease has already been associated with other infectious diseases such as periodontitis (DeStefano et al., 1993). It is only by considering all three possible causes for a disease that we are able to fully comprehend its etiology and find ways to treat it, or ultimately, prevent it from developing in the first place. B. However, they stress the importance of inflammation in the development of PB, and suggest using an anti-inflammatory strategy to help prevent or control the progress of PB. The eagle eye is among the strongest in the animal kingdom, with an eyesight estimated at 4 to 8 times stronger than that of the average human. In a sense, we are involved in a never-ending arms race where neither the host nor the pathogen ever gets the upper hand for too long. DDT had caused problems for the bald eagle because it altered the bird's nervous system. A Bald eagle only weighs around twelve pounds but can weigh even as little as six pounds. Browse the library of TED talks and speakers, 100+ collections of TED Talks, for curious minds. That's what we're talking about today in Wonderopolis! Alopecia means loss of hair and the natural type that so many men experience is androgen, meaning it’s caused by steroid hormones. The researchers suggested preventing PB by controlling the microorganisms that inhabit the scalp, which have been shown to be potent elicitors of the immune response (Piérard-Franchimont, 1995, cited in Piérard, 1996). The second study examined 135 pairs of twins found in an Adult Twin Registry in Japan (Hayakawa et al., 1992). Why we go bald: an evolutionary hypothesis. Acta Derm Venereol 79: 347-350. Hairs probably first evolved as a mechanoreceptor used to sense the outside environment. Mahé, Y. F., Michelet, J. F., Billoni, N., Jarrousse, F., Buan, B., Commo, S., Saint-Léger, D., Bernard, B. Find out why these majestic birds are so cool. In humans, although hair is not essential, some hairs actually have specific functions. wyatt Wonders, “Why do people go bald?” Thanks for WONDERing with us, wyatt! The notorious pesticide DDT – responsible for the decline of the honeybee, among others species – has also taken its toll on the U.S. eagle population. Mostly bald, you’re an ape, descended from apes; your features and actions are carved or winnowed by natural selection. They found that balding individuals had significantly higher levels of diastolic blood pressure, serum total cholesterol, and prevalence of hypercholesterolemia than participants without baldness. The presence of immunoglobulins on the scalp indicates that an antigen is present, perhaps a microbe. But the scalp is particularly shiny because of the sebaceous glands. Finally, light may further exacerbate the problem by acting on bacteria to produce porphyrins, which also excite the immune system and cause inflammation. Not all people that are genetically predisposed to male pattern baldness will go totally bald. As I have shown, we are still far from determining with certainty the exact causes of pattern baldness. Sueki, H., Stoudemayer, T., Kligman, A. M., Murphy, G. F.  (1999)  Quantitative and ultrastructural analysis of inflammatory infiltrates in male pattern alopecia. Hamilton, J. The problem with this study, aside from the small sample size, is that subjects were selected on the basis of having a previous diagnosis of psoriasis or atopic dermatitis. Furthermore, within the bald populations, individuals with higher degrees of baldness had higher diastolic blood pressure than those with fewer degrees of baldness. PB baldness is not simply a consequence of aging, as once thought; instead, it is an inflammatory disorder of the scalp. Genetics also seem to play a role in the development of PB. For my final project, I decided to explore male pattern baldness from an evolutionary perspective. Top Answer. This link is suspiciously similar to the link between heart disease and periodontitis (DeStefano et al., 1993). A healthy human scalp contains 90% anagen hairs, and about 10% catagen or telogen hairs. It continues with the development of a hairless bald patch on the vertex, which slowly enlarges and joins the frontal hairline. Most of the skin on your body is actually covered with tiny hairs called vellus hairs that give your skin a slightly velvety, peach-fuzz look. I’ve included my entire (lengthy) paper below. There is little recession of the front hairline; instead, there is a diffuse hair loss throughout the midscalp (Odom et al., 2000). This is important because other studies have found that high levels of lipoprotein (a) are by themselves a risk factor for heart disease (Ari & Yigitoglu, 1997, cited in Sasmaz et al., 1999). He reasoned that over generations of males picking less hairy mates, the overall population, of both males and females, became less hairy due to genetic mixing. The density of follicles was not noticeably diminished, although some were destroyed by the intense inflammatory infiltrate. This differentiates it from other types of hair loss that are attributed to disease. The anagen phase continues for a period depending on the type of body hair, then slows down for the resting, or telogen, phase. Therefore, humans evolved to fill their mobile needs by losing the fur over the course of generations. They also found porphyrins in 58% of PB subjects and in 12 % of controls. (1958)  Age, sex, and genetic factors in the regulation of hair growth in man: a comparison of Caucasian and Japanese populations. This fact is interesting, because current research has also presented supporting evidence for infectious causation of heart disease (Ewald & Cochran, 2000). Androgens are responsible for promoting the growth of pre-pubertal vellus hairs into pigmented terminal hairs (Sinclair, 1998). They suggested that PB was not a direct risk factor for heart disease, but instea,d it worked as a marker for some other underlying risk factor. Unless women start finding bald men attractive, and men with hair unactractive. Why Do Some Men Go Bald While Others Don’t? The presence of inflammation in the scalps of balding patients is now beginning to be recognized. It is likely that genetic, infectious, and non-infectious environmental causes play a role in the development of the disease. Z., Wolff, K., Freedberg, I. M., Austen, K. F. (Eds). Ann Dermatol Venereol 127:1534-1536. Therefore, if PB is shown to correlate with heart disease, and if heart disease is shown to be caused by pathogens, then it is possible that pathogens are also responsible for the development of PB. Answer. However, because most chronic diseases take a long time to develop and do not have a clear pathogenic cause, we often overlook the possibility of infectious causation in the development of the disease. From Setty, 1970. However, this study failed to distinguish between individuals with a full head of hair or those with PB, so they might have also overestimated the real figure. (2001) have found a significant association between PB and a gene that codes for an androgen receptor. Periodontitis is an inflammation of the soft tissues around the teeth caused by bacteria (Encyclopædia Britannica, 2001). The first twin study was conducted with 18 pairs of white American twins registered in the Twin Registry files (Lynfield, 1974). Interestingly, D. follicularum has long been known to cause mange in animals, a disease characterized by inflammation, itching, thickening of the skin, and hair loss (Encyclopædia Britannica, 2001). My guess is that the natural selection theory will prevent a bald future. With every completion of the hair cycle the hair follicle becomes progressively smaller, and thus the hair they produce becomes smaller as well. Exceptions are generally caused by: Domestication, thanks to the intensive breeding process their ancestors were subjected to. Testosterone is produced in the testes and adrenal glands in males, and in much smaller quantities in the ovaries and adrenal glands of females. Herrera, C. R., Lynch, C.  (1990)  Is baldness a risk factor for coronary artery disease? Androgens are hormones that play an essential role during adolescence in inducing and maintaining secondary sexual characteristics such as pubic and other body hairs. Young, J. W., Conte, E. T., Leavitt, M. L., Nafz, M. A. Schroeter, A. L.  (1991) Cutaneous immunopathology of androgenetic alopecia. Since PB begins in areas that are most frequently exposed to the sun, Young and coworkers argued that light may excite porphyrin production by the resident flora, producing an inflammatory reaction. Kligman (1988) was the first to notice the difference in the degree of inflammation in balding as opposed to control subjects. PB affects about 30% of Caucasian men in their thirties, 40% in their forties, and so on until age 70 (Sinclair, 1998). But what a special simian you are. You asked about animals. As mentioned above, it appears that antibiotics may help in reducing hair loss by reducing the number of microbe flora and reducing inflammation (Piérard et al., 1996). Most importantly, the most distressed balding men are those who are younger and are romantically unattached—men who are looking for a mate. Piérard, G. E., Piérard-Franchimont, C., Nikkels-Tassoudji, N., Nikkels, A. F., Saint Léger, D.  (1996)  Improvement in the inflammatory aspect of androgenetic alopecia. British Journal of Dermatology 127: 239-246. translators. Trevisan, M., Farinaro, E., Krogh, V., Jossa, F., Giumetti, D., Fusco, G., Panico, S., Mellone, C., Frascatore, S., Scottoni, A., Mancini, M.  (1993) Baldness and coronary heart disease risk factors. DHT is catalyzed by testosterone by a 5α-reductase enzyme present in hair follicle cells. Ewald, P. W., Cochran, G, M.  (2000)  Chlamidia pneumoniae and cardiovascular disease: an evolutionary perspective on infectious causation and antibiotic treatment. When one begins to research the life of an eagle they can end up with all sorts of fascinating thoughts. Journal of the American Medical Association 32: 524-525. Pattern baldness (PB), also called androgenetic alopecia, is characterized by a progressive patterned hair loss from the scalp, which begins usually during the twenties or thirties (Odom et al., 2000). Y ou are an animal, but a very special one. Compared to other apes and indeed all other mammals, humans are practically bald, and this may have allowed our species to thrive Share on Facebook Share on Twitter Men go bald for a variety of reasons. Journal of Clinical Epidemiology 43: 1255-1260. Mahé and coworkers argue that for each individual, the causal agent may be different (androgens, microbial flora, stress, genetic imbalance). The Darwinian Homo sapiens lost their hair because males found less hairy females sexier. Researcher and dermatologist Cato Mørk explains how hormones affect the manes of so many men. He concluded his paper by stating that PB is an “inflammatory disorder that should not be construed as premature aging.”  He hypothesized that suppression of the inflammation could decelerate the process of PB. It is likely that their results overestimated the actual number of twin concordance because a preexisting skin disease may have contributed to the development of PB. Küster, W., Happle, R.  (1984) The inheritance of common baldness: Two B or not two B? Environment and resources effect every everything on this planet why should humans be any different. In Fitzpatrick, T. B., Eisen, A. A pilot study with an antimicrobial lotion. Journal of the American Academy of Dermatology 26: 926-931. The first phase is the anagen, or growing phase, which lasts about 3 years. Middle European Journal of Medicine 111: 976-977. Some people have a lot of hair and, well, some people don't! New York: McGraw-Hill Book Company. Pubic and auxiliary hairs help in disseminating odors, eyelash and eyebrow hairs protect the eyes, scalp hairs protect the head from the sun and are used for beauty, and beard hairs in men are used for sexual displays. Second, there is growing evidence of the presence of inflammation in the scalp of balding individuals (Kligman, 1988; Young et al., 1991; Jaworsky et al., 1992; Piérard et al., 1996; Sueki et al., 1999; Mahé et al., 2000). Cash, T. F.  (1992)  The psychological effects of androgenetic alopecia in men. The above-mentioned articles suggest a link between heart disease and PB. Piroctone olamine is a powerful antifungal agent and triclosan is a common antibacterial. Learn more about the (1992) Intrapair differences of physical aging and longetivity in identical twins. Some… Lord, M.  (1998) Is a common bug cutting your rug? They observed that the degree of hair loss was identical in 92% of monozygotic twins, while it was identical in 67% of dizygotic twins. As a Senior in college, I took a class on evolutionary medicine with Professor Paul Ewald. For most men, losing your hair is an inevitable side effect of aging. Experts respond to questions about autoinflammatory diseases, 2020 Boston Children’s Hospital Autoinflammatory Disease Family WorkshoP, Health­-related Social Media Use by Parents of Children with Rheumatic Diseases, The Rheumatology Image of the Week Project (#RheumIOW), Managing Your Autoinflammatory Disease: Lifestyle and Wellness Workshop. As suggested by the name, hair loss in PB follows a specific pattern, as described by Hamilton (1951, cited in Sinclair, 1998). Paradoxically, the same androgens that promote adult body hair growth also seem to be involved in reducing scalp hair count and in the development of male pattern baldness. It has been shown that the excess of DHT in the scalp enlarges the sebaceous glands (Lattanad & Johnson, 1975; Bergfeld, 1995, both cited in Mahé et al., 2000). In PB, the hair loss is a result of an increase in the ratio of telogen to anagen hairs and the miniaturization of the hair follicle (Rushton et al., 1991; Sinclair, 1998). DeStefano, F., Anda, R. F., Kahn, H. S., Williamson, D. F., Russel, C. M.  (1993)  Dental disease and risk of coronary heart disease and mortality. Encyclopædia Britannica (2001)  “Porphyrins.”  Britannica.com. Hair loss or fur loss can be seen in several animals, including coatis, Andean bears and cats of various species. Since a man with hair is more attractive (to some women) the genetic procreation will keep the hair gene in the gene pool, thus ensuring the survival of haired humans. Scientists have long pondered, why do some people lose their hair, and how can we bring it back? Sasmaz, S., Senol, M., Ozcan, A., Dogan, G., Tuncer, C., Akyol, O., Sener, S.  (1999) Journal of the European Academy of Dermatology and Venereology 12: 123-125. Human hair comes in two basic types: terminal hair, which grows on the scalp, eyebrows and eyelashes, and vellus hair, which is found everywhere else. (2000)  Androgenetic alopecia and microinflammation. (1991) found immunoglobulin M or C3 (or both) present on the basement membrane of 96% of individuals with PB and on 12% of controls. It works by blocking the conversion of testosterone to DHT, and thus reduces scalp and serum DHT concentrations. The eagle has the longest life-span of its species. New York: Academic Press, Inc. Hamilton, J. A longitudinal study conducted in Italy with 872 men set out to examine the relationship between PB and heart disease over a 15-year period (Trevisan et al., 1993). This is unlikely since baldness has been shown to have negative effects on body image satisfaction (Cash, 1992). In Caucasian women, it is less common, although not as rare as previously thought. Further support for the increased risk of heart disease with PB came from Sasmaz and coworkers (1999) who analyzed the difference of lipid parameters in 41 men with PB and 36 age-matched controls. Hairs then enter the catagen phase, which is a controlled regression of hair growth, a transitional phase between the growing and resting phase that lasts 1 or 2 weeks. The DDT created an abundance of calcium in the eggshells too, which led to brittle eggs that easily snapped when delivered. They concluded that the specific variation of the androgen receptor gene is necessary, but not sufficient for the development of PB. The first is minoxidil (Rogaine), which does not require a prescription. Beyond that, the main difference between hair types is how long they grow for before the follicle runs out of steam. Less than 5% appear to “divorce”, much less than the national average among humans. We can now see that predicting baldness isn’t as simple as just carrying the X-linked baldness gene or not! The human scalp normally contains 100,000 hairs that follow a specific growth cycle (Odom et al., 2000). Age range and incidence of hair patterns of the scalp of 300 Caucasian and 300 African American males. The fourth possibility is to take medication. Because hair is not essential for survival, bald individuals are able to live healthy lives despite their lack of scalp hair. Genetic instructions may code for the production of excess DHT, which enlarges the sebaceous glands and provides a more hospitable habitat for microbes. This sounds like a logical argument when you have only half the facts. In women, the hair loss pattern is different (Figure 2). Furthermore, he noted that bald people often report scaling and itching during the early stages, presumably because of the inflammation. Why are humans Eagles predators? Hair plays no vital function in human physiology, as we can live perfectly well without having any hair (Bertolino & Freedberg, 1987). Why we go bald: an evolutionary hypothesis Pattern baldness (PB), also called androgenetic alopecia, is characterized by a progressive patterned hair loss from the scalp, which begins usually during the twenties or thirties (Odom et al., 2000). Sueki and coworkers (1999) noticed a significantly greater number of lymphocytic inflammations around the hair follicle cells in PB patients than in controls. PB was initially thought to occur as a … The Journal of Investigative Dermatology 116: 452-455. Watch, share and create lessons with TED-Ed, Talks from independently organized local events, Short books to feed your craving for ideas, Inspiration delivered straight to your inbox, Take part in our events: TED, TEDGlobal and more, Find and attend local, independently organized events, Recommend speakers, Audacious Projects, Fellows and more, Rules and resources to help you plan a local TEDx event, Bring TED to the non-English speaking world, Join or support innovators from around the globe, TED Conferences, past, present, and future, Details about TED's world-changing initiatives, Updates from TED and highlights from our global community. (Eds)  The Biology of Hair Growth. Why do bald heads get so oily? Share on Reddit. A. What we do know is that men who are bald are regarded as more mature and less aggressive than other people,” he says. 2001). Sure, there's a lot of variation among human populations. Clinics in Dermatology 6: 108-118. Regelson speculated that the scalps of some individuals are sensitive to the mites, and thus become inflamed and interrupt the normal hair cycle. Balding is a complex trait and scientists are still working to discover all the genes behind it. A review of the literature. It has been proposed that the same bacteria that cause periodontitis are the causative agents of heart disease (Mattila et al., 1989, cited in DeStefano, 1993). Kligman explained that the chronic inflammation prevents the anagen follicles from being fully reconstructed during each new cycle, which explains the shortening of the anagen phase in PB. Animals, like humans, do go bald. Share on Facebook. The numbers must be read as the maximum possible genetic involvement in the development of the disease, not as its actual genetic contribution to because pathogens or other common environmental factors may contribute significantly to the disease. Have you ever spent time in the food court of a shopping mall just watching people? Hair loss or fur loss can be seen in several animals, including coatis, Andean bears and cats of various species. They concluded their paper by suggesting the use of antimicrobials to reduce the number of natural flora and a reduction in sun exposure to help control the extent of PB. Ellis et al. It occurs when hair follicles shrink and only grow tiny hair that doesn’t stay viable for long periods of time. The Life of an Eagle and Why Humans Are Very Similiar. . Eagles' high-flying lifestyle requires better vision than humans need, and the physical properties of our eyeballs limit us to 20/10 or 20/8 vision at best. The source of pattern baldness is genetically linked, and there are no known cures. Sarthak Sinha explores the basics of baldness. Why would a gene for cancer not be weeded out by natural selection? Sorry, your blog cannot share posts by email. 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