Class Note for ANT 275 with Professor Bindon at UA-Race, Ethnicity Human Variatn(2)
Class Note for ANT 275 with Professor Bindon at UA-Race, Ethnicity Human Variatn(2)
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Date Created: 02/06/15
The Distribution of Human Differences Races Clines Populations YABLE I sruDiEs or RACIAL APPoRnoNMENr 3 11991011 wpuiunon 39llndeuul may Daia siaimic race Lewomlri i972 i7 piaoa groups snannon inrorrnarian e a a a a5 4 measure arrerw wan in piaoa groups a snannon inrorrnaiion 2 Bel 4 on a La i i 775 4 an 2790 7 proreins 5 measure Hedrlck enzymes genlc sirniiarriy Loner pairea comparison ei ana Raycnouanuryw e2 proiein 23 pioaa Nel39s sianaara geneiic i5 04909 ai M50 i 052 nee but parsing or variance unclear yrnan cnaiaanorry ana i4 proiein o piooa Cnakrebcny nierarcni e 1H 5 439 2 me a a2 7790 a New was group 2 HLA gene diverle Exoomer smcuse ana a4 WDNA ioci aaorsirapping null i5 7722 ow a H e 74 7750 7 auarrroAs i 992 aisrriauiien assumpilo Dean ana coworkers i i5 RFLP loci unweignrea averaging 9 54 u lquot 3 Win 5 i 094 or aiieie rreauencies arpuiani ana coworkers 74 me an Boomrap rnurripie aiieii in Dell 7 3 e5 5 34 5 i 097 rnicrasarreiire loci rreauency cernpariso eieisraa Mincn ana a4 rnvDNA locl 22 aoomrapping V ana i2 5 miDNA e i Bi 4 rnvDNA Cavalllsi39oi39m wee piaiieiic rnioNA unciear 52 7 V miDNA a5 5 V singie nucieaiiae poiyrnorpnisrns aurasarnai iia V k eieisraa Mincn ana 2L amesarnai iaci aaoisrrapping39 2 u u 2auiosm 97 a Cavalllsl39orza i we in V crrrornasprne aurasrn i4 0 V auiosrn rnierosarreirre iaci 2 5 V as 5 V Genetic variability attributed to race 28 527 one analysis greater than 22 Table 1 Analyst at molecular variance AMOVA Eurasia which encompasses Europe the Middle East and CentralSouth Asia is treated as one region in the veregion AMOVA bul is subdivided in the sevenregion design The World I597 sample mimics a previous study 6 Variance compunents and 95 con dence intervals 96 Number Number of Sample nf Among A regions populaiicni Within populations pnpuiaticms 3921 within reginns E Wulld l 52 94 6 9173 918 54 52 57l World 5 52 932 929 935 25 24 26 World 7 52 94193 8 94 3 24 23 25 wmmaqr 5 l can 893 90 2 some 53 Atria l 6 96 9 96 I 97 l 312933l Eurasia 1 al 5359543an 151416l mm 3 21 nsawa 2954 Lgii l13 kuropc i a 99399i994j uiiob oqi Middle Last l 4 38 71985 5398 8 131214l CenLral Suulh Mia r 9 18 6 US 5 98 a 14 1 z 15 East Asia i is 93 719317909 131 i 14l Oteanld 1 z 93 5 1928 941 6 4 is r 7 2 America l 5 88 4 871390 H6l LO l2 3 Region is the analog for race in this study variability attributed to race is Among regionsquot Distribution of Genetic Variation 01 05 difference in DNA between any two people Race and Genetic Variation This is 5 of the 55 of DNA thaty rb twe q ces accounts for 5025 of human DNA 39quot quot7 V 7 5 Between Populations So how are racial markers distributed Hair Head Shape Nose Shape Body Build Skin color It is dif cult to form anyjudgment as to how the hair on the head became developed to its present great length in many races Our semihuman progenitors were not furnished with long tresses which must therefore have been a late acquisition This is l kewise indicated bythe extraordinary difference in the length ofthe hair in the different races in the negro the hair forms a mere curly mat with us it is of great length and with the American natives it not rarely reaches to the ground Some monkey species have their heads covered with moderately long hair and this probably serves as an ornament and was acquired through sexual selection The same view may perhaps be extended to mankind for we know that long tresses are now and were formerly much admired as may be observed in the works ofalmost every poet St Paul says ifa woman have long hair it is a glory to herquot and we have seen that in North America a chief was elected solely from the length ofhis hair Darwin 1871 Cephalic index Cranial Breadth divided by Cranial Length 2 long heads 4 5 broad heads Populations native to cold climates have larger and relatively broader skulls than populations in warm climates The distribution of many racial features is determined by various environmental factors Size and shape of the nose Size and shape ofthe skull Body Size and Shape Skin Color utsmmmm m wuth no nlu39xxulzn mm Lower the value thetaller more narrow the nose adapted to hot dry environments Higher the value the shomerand broader the nose adapted to hot humid The ltalian Anthropologist ani standing w three adult Vedda of pygmoid stature Bergmann39s Rule 1847 Within a polytypic warmblooded species the body size of the subspecies usually increases with decreasing mean temperature of its habitat An increasing body size means several things There is an increase in the amount of metabolizing tissue therefore internal heat gain is greater There is an overall decrease in the surface area to mass ratio meaning that heat loss is reduced Bergmann s TOTAL Rue In Y756305X 3970 Humans From Roberts 197818 EUROPEAN V 843 414X 0 AMERICAN 500 5327 123x wei ht sauonaowrn 9 vson 1oox AFRlCAN V 878 2512 X o 20 4o 60 so mean annual temperature F Allen39s Rule 1877 o In warmblooded species the relative size of exposed portions ofthe body decreases with decrease of mean temperature An increase in exposed portions ofthe body increasing surface area also has several natural concomitants Keeping mass constant surface area is increased by assuming a more linear formtaller with long slender arms and legs This is especially important for humans since heat loss from evaporation of sweat is greater than in any other animal and evaporative loss is directly proportional to the amount of exposed surface area 39 Short broad v1 Native American from extreme South America almost 60 South Tall slender Dinka from the upper Nile 10 North Stature Equalized r Allen s Rule in l g39 5359 r7 ax Humans 550 From Roberts 197823 AMERICAN 530 V540B 293X relative sitting height ggm POID 0 51 v5664 00 772x NEGROID 190 v5587r 750x I I l I 10 30 50 7o 90 mean annual temperature F mummmm 1ruwma Not an accident thatt ere are 8 divisions Biasutti preferred a 16 race system u an mum 1ch run Skin The body s largest organ Functions in many ways Therm oregulation Protection from physical and chemical Injury Protection from invasion by microorganisms Manufactures essential nutrient Skin Color As one ofthe most conspicuous human polytypic variations skin color has probably attracted more scholarly attention than any other aspect of human variability Skin color has served as a primary feature in most systems of racial classification Genetics of Skin color Skin color is a polygenic trait meaning multiple genetic loci are involved in determining skin color Multiple genes working together produce a continuous distribution in a Bell Shape curve of degrees of light to dark Recent work suggests many genes working together in very complex additive and nonadditive combinations that affect the synthesis ofmelanin One major gene has been identi ed 7 Melanocortln 1 receptor MCiR on chromosome 16 Measurement of Skin Color By the latter half of the nineteenth century while anthropologists still had no clear idea of the undertying causes of pigmentation they began to devise measurement techniques to use skin color in racial classi cation Broca established a 34 tone scale which was simpli ed by his student Topinard These techniques were used into the 20m century until the introduction of the reflectance spectrophotometer in the early 19508 Reflectance Spectrophotometer A Reflectance Spectrophotometer shines a light of a specific wave length using a filter and measures the intensity of light reflected by the skin The technique involves alcohol wash of the skin on the inner upper arm allow time for local circulation to return to normal shine light and measure re ectance Reflectance Spectrophotometry Melanin Skin color is Continuous Mean dot andsd bar of skin color for 22 populations 1 v V The primary determinant of variability in human skin color is the amount density and distribution ofthe pigment melanin Melanin has a dark brownpurpleblack V39 Sudan Banlu TuaEkonda I I I I th kum color that is intensified by denser 39 Miim mw compaction of the melanin granules in 39 cm the cells of the upper layers of the skin 5 2 0 3390 4 0 5390 3 7 3 Darker 4 g1l f Pciucniiigiz iii 1 Ijhl reflected Structure of the Epidermis Melanin Metabolism Tyrosinase Tyrosinase Tyrosine Dopa Dop aquinone stratum corneum 39gt Deucodopachrome 5787Cysteinyldopa 4 567Dihydroxyindolei Zicarboxylic acid x l 1 it Do achrome lquot I I 5757Cysteinyldopai stratum granulosumr y stratum h spinosum Mali ian 5 pg basal layer 7 l layer l stratum I basale II I x keratinocytes l I x qumgne 567Dihydroxyindole i l I a Benzothlazme x I I I I I I I I I I I I I i i I Intermediaries l I I t t I l i39 39 i39 i39 i V V 39 Lx gt contributes to melanocyte p copolymerization Epidermis from Robins 1991 2 Melanin Synthesis 2 Melanin Synthesis Dopaquinone undergoes a series of nonenzymatic reactions and rearrangements forming the different The metabolic pathway to melanin is molecules that are copolymerized to make up one extremely complicated involving several intermediate steps ofthe types of melanin Starts With the amino aCid terSine OXidized Eumelanin is the dark brownpurpleblack compound found by the coppercontaining enzyme tyrosinase in skin and hair to dihyd roxyphenylalanine dope and then to Phaeomelanin is the yellowtoreddishbrown pigment dopaquinone which is present in red hair A mutation to the gene for the enzyme tyrosinase Both forms of melanin combine with other proteins to form the melanosome that is distributed from the melanocyte to surrounding cells that produces a protein with decreased functionality will result in a reduced production of melanin In the extreme this produces a genetic form of albinism Distribution of Skin Color 244 um m wpvcimlamkei W my wt ccllsclvdln a Emu in W v m Vmilmmaieesz mm mm mm W boil ln olavammmhlt 30m ml mm f Lighter skin Skin Re ectance quota 3 Darker I l l l 1 5km 40 3o 20 1o 0 10 20 Southem Latitude Hemisphere l y l l 30 40 50 60 Northern Hemisphere Distribution of Skin Color 3 The clinal nature of skin color distribution suggests an association with environmental factors varying with latitude Ultraviolet Radiation in particular the quantity of UV rays striking the surface of Selection Favoring Dark Skin in Tropical Regions Selection favoring high levels of melanin pigmentation in areas of high Ultraviolet UV radiation may involve several selective agents Sunburn can cause skin lesions and infections preventing some degree of heat Skin cancer is found to be prevalent among light skinned individuals in tropical latitudes In Nigeria and Tanzania no albino over the age of 20 years was found to be free of malignant or premalignant skin lesions In Tanzania chronic skin damage was found in every albino infant bythe end of the first year of life This high rate and early evidence of skin damage suggests that cancer may have been a strong selective pressure in tropical areas loss the earth from the sun Skin cancer Temperature Secondary folic acid deficiency Folate Photolysis Skin Cancer Folic Acid Deficiency UV light causes denaturization a chemical breakdown of Folic Acid circulating in the blood This can induce a deficiency even if the diet supplies adequate folic acid Deficiency symptoms include anemia infertility and birth defects especially neural tube defects Reduces sperm production in men High melanin content in the epidermis can protect circulating Folic Acid thereby selecting for dark skin in low latitude areas Selection favoring depigmentation in higher latitudes As early members ofthe genus Homo left the tropics and encountered new environments in higher latitudes depigmentation became adaptive Selection favoring low levels of melanin pigmentation in ecosystems where there are low levels of UV radiation are thought to primarily be affected bythe regulation of Atamin D synthesis Regulation of Vitamin D Vitamin D in the body is derived primarily from the skin and secondarily from the diet Vitamin D is synthesized in skin by the action of UV B Precursor molecule is 7DHC or 7 dehydrocholesterol which occurs in the strata granulosum and basale ofthe epidermis UVB exposure causes a photochemical non enzymatic conversion of7DHC into previtamin D ngh melanin content in skin reduces UVVB ekposure and cuts pnotocnemical conversion Regulation of Vitamin D 2 Provitamin D3 istransformed into vitamin D by a temperature dependent process over 23 days Vitamin D then diffuses into the blood vessels of Potential for synthesis of previtamin D3 in lightly pigmented human skin based on annual average UV we N EEZPQ S the dermis 77 The liver and kidney further transform the Vitamin zn 13mm ZuluJ quotmsmum W D into 125dihydroxyvitamin thich is the most quot 39 mquot mquot n quot quot39quot quot quot 39quot quotquotquot active form ofthe vitamin my mmnbym The function of Vitamin D is to actively cause calcium absorption across the wall of the small intestine into the blood stream Sad9K ramva Regulation of Vitamin D 3 Calcium is used for bone and tooth development as well as for nervous and muscle action The skeleton serves as a calcium reservoir lf calcium levels in intracellular uid drops hormones are released to cause resorption of bone placing calcium into circulation Regulation of Vitamin D 4 A de ciency of Vitamin D in infants and children causes Rickets in adults a de ciency causes osteomalacia Rickets refers to a defect in the calci cation ofgrowing bone so that the bones are structurally weak and unable to withstand mechanical pressure symptoms include muscle weakness deformlty of tne long bones including powed legs knucklelike proiections along tne rib cage racnitic rosarv detormities of tne pelvis tnat are often permanent 7 Lung burle derormitv impairs locomonon e PElvlc distortion can make cnildoearing dangeruuswputentlally killing motner and oaov Prlor to Widespread vitamin D supplementation in tne lgsos Black women in tne u s snowed nearlv 8 times greater pelvic deformlty tnan Wnite women Rickets PELVIC INLET a AREA 1152cm 2 b AREA 65 cm Severe Childhood Rickets Normal Predicted shading of skin colors for indigenous humans Regulation of Vitamin D 5 Assuming ancestral dark skin as hominids moved to higher latitudes selection would have favored depigmentation to improve Vitamin D synthesis Need to consider the effects of clothing on northern latitude populations where selection against dark skin would be increased because of less skin exposure 0 Also the animal organ and fish diets in high latitudes may contribute more dietary Vitamin D Gradation of skin colors for known Predicted shadIng of skIn colors for Indigenous humans Indigenous human populations Gradation of skin colors for known indigenous human populations Races Clines or What Highly visible characteristics like skin color hair form nose shape body size show strong clinal variation conditioned by natural selection from the relevant environmental factors All genetic analyses show race or region accounts for very little global variability with most differences occurring between individuals within populations
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