Biological Basis of Morphological Variation of Non-Metric & Metric Characters | Anthropology Optional for UPSC PDF Download

Introduction

The study of racial differences is important for a variety of reasons:

• It provides us with many characteristics of human groups indicating ancient and prehistoric relationships among different people.
• Racial differences are examples of precise biological adaptations to the environmental needs that help in the understanding of human evolution, and
• The association of the racial traits with certain diseases represents an important medical problem

Early racial classifications were given by Linnaeus (1735), Bufon (1749), Blumenbach (1781) and Cuvier (1790). Linnaeus dealt with a classification of human diversity by using subspecies which he called human varieties: America, (Reddish), European (White), Asiatic (Yellow), Negro (Black). Blumenbach had a passion for the natural sciences, including anatomy and the variations of the human race.
He made a collection of biological and ethnographic objects and articles, incorporating basic differences in skin pigmentation and hair colour depending on facial features, shape of teeth, and skull morphology to identify five human races consisting of Caucasian, Malaysian, Ethiopian, American, and Mongolian. Though this classification was revised by later scientists, it laid strong foundation for undertaking studies of human variations. These early classifications, later called races, were determined by comparisons of skin colour, face form and skull shape.

Humans are a Polytypic Species

Monotypic species is a type of species with its members belonging to a single subspecies displaying at least one of the following properties:

• All members of the species are similar and cannot be subdivided biologically into distinct subcategories
• The individuals may vary considerably but the variation is essentially random and genetically meaningless
• The noticeable variations among individuals follow a pattern, with no clear dividing lines among separate groups.
  On the contrary, a polytypic species has two or more subspecies. These are separate populations that are more genetically different from one another and reproductively isolated; gene flow between these populations is much reduced leading to genetic differentiation. Thus it is assumed that humans are not a monotypic species, because the third clause/property is explainable on the basis of hybridization due to human migrations. Anthropologists have considered humans a polytypic species on the basis of morphology.

Origin of Modern Humans and their Geographical Differentiation

Human evolution tells that modern humans are the resultant of few hundred thousand years of human migration and population bottlenecks. Genetic analysis tells us that modern humans arose in Africa about 200,000 years ago and migrated northwards out of the continent about 50,000 - 100,000 years. As the early migrants spread out across the earth, communities were isolated and placed, by the environment, under considerable selective pressures.
This would have included food supply, disease, temperature, altitude, ultraviolet radiation and so on. In equatorial regions, strong sunlight and high temperatures strongly favour dark skin (to protect against UV-mediated destruction of the essential vitamin folate) and short curly hair (which keeps the head cooler). When they migrated out of Africa to areas where light intensity is lower and the temperature is cooler, there is less risk of UV-induced folate deficiency. At the same time, dark (melanised) skin can impair vitamin D synthesis, which is essential for calcium uptake and hence skeletal development.
For this reason those early people who moved further north lost their basal melanisation (i.e. became white), and also had less use for curly hair. Since these people lived in geographically isolated communities these traits concentrated within these populations, leading to the emergence of distinct-looking races. These groups could not evolve into new species as insufficient time has not allowed the genetic divergence that would be required to create novel species. As Biologists we can sort out some likely causes of speciation and race formation are the micro-evolutionary processes like mutation, recombination, natural selection, genetic drift, gene flow and nonrandom mating (www.thenakedscientists.com).

• Mutation: Heritable change in the genetic material.
• Recombination: New recombination of alleles.
• Natural selection: Favourable heritable variations that survive and provide individuals higher reproductive rate than others in the populations in different specific environments. The frequency of these variations increases in the next generation. Natural selection relates to the concept of fitness. Fitness is an individual’s lifetime reproductive output.
• Genetic drift: It refers to the statistical drift over time of gene frequencies in a population due to random sampling and other chance events that occur each generation.
• Isolation: Reproductive isolation in which members of a population become separated from another population by geographical or cultural barriers that prevent the interchange of genes between the separated populations.
• Non-random mating: This occurs when mating individuals are genetically related to one another, or phenotypically more (or less) similar to each other than two individuals chosen at random.
• Genetic admixture: Or gene flow will bring in different genes from other populations. This process however retards speciation and racial differentiation.

Biological Races

• The word ‘race’ has probably been drawn from the Arabic root ya’ys (meaning head or beginning) and was first used by the French scholar, F. Bernier (1684). The term, “race” in current biology has several meanings. In the 19th century, and before, the word “race” was often used in biology as a synonym for a division below the level of species. Today some biologists still use the word race to refer to kinds or strains of animals, and more often, of plants. Historically, there have been biological definitions of races. By the nineteenth century, western biologists separated human beings into various racial classifications under the assumption that there were distinct biological differences between them, similar to the differences between species or subspecies.
• As a biological term, race denotes a subspecies consisting of a more or less distinct population with anatomical traits that distinguish it clearly from other races. Sewall Wright (1978) suggested that human populations that have inhabited separate parts of the world should be considered as different subspecies. However, it is customary to use the term race rather than subspecies for the major subdivisions of the human species as well as for minor ones. It has been argued that it does not require a trained anthropologist to classify an array of Europeans, West Africans and Japanese with 100% accuracy by morphological features like skin colour, and type of hair despite much variability within each of these groups that every individual can be distinguished from every other.
• This typological approach to race was popular in the 19th Century and the first half of the 20th Century. The review of papers published in a renowned physical anthropology journal, reveal that 78 percent of the articles in the 1931 Journal of Physical Anthropology employed bio-racial paradigm, but in later years only 36 percent did so in 1965, and just 28 percent did in 1996. This only shows that emphasis of physical anthropologists changed from typological approach to studies related with the mechanisms and causes that caused human biological diversity. But race remain a valid biological entity.

Definition of Race

• According to Hooton (1926) race is “a great division of mankind, characterised as a group by sharing certain combination of features, which have been derived from their common descent, and constitute a vague physical background, usually more or less obscured by individual variations, and realised best in a composite picture.” Boyd (1950) defined race as a population which differs from other populations with regard to the frequency of one or more of the genes it possesses. Garn (1960) defines it as a breeding population, partially isolated reproductively from other breeding populationsMayr (1969) defined race as, “a subspecies is an aggregate of phenotypically similar populations of a species, inhabiting a geographic subdivision and differing taxonomically from other populations of the species.”
• According to Dobzhansky (1970) races are “genetically distinct Mendelian populations. They are neither individuals nor particular genotypes, who differ genetically among themselves.” Vogel and Motulsky (1986) define race as a large population of individuals who have a significant fraction of genes in common and can be distinguished from other races by their common gene pool. According to Templeton (1998), a subspecies (race) is a “distinct evolutionary lineage within a species, genetically differentiated due to barriers from genetic exchange that have persisted for long periods of time.

Morphological Criteria of Race

Humans are often defined by easily observable physical traits like skin and hair colour, hair form, characteristic features of nose, eyes, lips and face. In the beginning, only this criterion was used for the purpose of human taxonomy. The morphological traits have polygenic inheritance, where genotype-phenotype relationships are not clearly known. These characters are adaptive in nature, and that is a fundamental criticism used against these traits to measure genetic distance between human populations. Oliver and Howells (1957) emphasised the use of metric traits and morphological averages as an exploratory device in human taxonomy. The morphological traits fall into two major categories:

• Somatoscopic traits, which do not easily lend themselves to exact measurement and based on visual observation alone.
• Anthropometric traits, which can be exactly measured based on standardized methods, like stature, head length, head breadth and other body measurements.

Skin Colour
The most visible characteristic is skin colour and has been extensively used as a racial characterisation. Skin colour determines the amount of skin pigments like melanin, melanoid, carotene and factors like haemoglobin, oxyhaemoglobin and optic effect due to scattering. The amount of melanin present is the major factor for the colour of skin, hair and eye, produced by specialised cells called melanocytes. In skin, after formation, most of the melanocytes come to rest in the germinative layer of the epidermis where they form melanin and distribute to the numerous cells around them.
Spectrophotometry technique is used as an accurate measurement of reflected skin colour. One can use colour charts available with paint companies and dyers for subjective skin colour determination. Body parts exposed to direct sun light will result in tanning of pale skin. A number of genes are known to determine skin/hair/eye pigmentation and these genes are Albino - TYR, Brown TYRP1, Pink-eyed dilution- OCA2, under white -SLC45A2, Ocular albinism - SLC24A5, Extension/recessive yellow - MC1R (melanocortin 1 receptor), Agouti - ASIP, Steel - KITLG, IRF4, SLC24A4, TPCN2.
Global distribution of skin colour reveal that different human populations of the world may be classified into three major groups:

• White Skinned People or Leucoderms: This category includes Europeans, some groups of Western Asia or Near East, Polynesians, North Africans, where the skin colour varies from white to light brown.
• Yellow Skinned People or Xanthoderms: They exhibit yellowish tinge in their skin. They include Asiatic Mongoloids, Bushmen, Hottentots and Armenoids.
• Black skinned People or Melanoderms: They are characterised by black skin colour and are represented best by Negroes.

Morphological Characteristics of Hair

• In humans, scalp hairs are generally shed every two to four years, while body hairs are shed more frequently. The number of scalp hairs averages 100,000– 150,000. Hair grows about half an inch (13 mm) per month, but not all areas of the head will necessarily grow hair to the same final length.

Hair Colour

• Majority of people have darker shades of hair colour. Different shades of colour for hair range from jet black to iron grey and snow white. Blonde and red shades are predominantly found in the Western Europe. There is a gradient of increasing blondness from South to North Italy. Red hair varies from a deep orange-red through burnt orange to bright copper. It is characterised by high levels of the reddish pigment pheomelanin and relatively low levels of the dark pigment.
• Scotland is the country with the highest content of red haired people, as about 13% of them have red hair. The genetics of red hair was first discovered in the year 1997. It has been discovered that the changes in the gene melanocortin-1 receptor (MC1R), found on chromosome 16 is responsible for producing this hair colour. The MC1R is a recessive variant gene. The dark hair colour shades vary from various shades of brown to black.

Hair Texture
Hair texture is traditionally divided into three categories:

• Coarse
• Medium
• Fine

Coarse hair, such as that of the scalp, contains an additional inner core called the medulla. Microscopic studies have been done on the thickness of hair shaft. Coarse hair has the widest diameter and very fine hair has the narrowest. On the basis of such studies, Professor S. M. Garn found that that diameter of fine hair is =56µ; medium hair 57- 84µ and of coarse hair 85µ and above. The white-skinned people have average hair shaft diameter less than 70µ, whereas Mongoloids have between 90 and 100 µ.

Hair Form
There are about 12 types of head hair forms: Straight, slightly wavy, long wavy, wide wavy, narrow wavy, curly, crinkly, loose woolly (matted), tight woolly or frizzly, tufted, peppercorn, spiral. These categories have been broadly categorized under three major groups

• Leiotrichous: These are further of three types
  (a) Stretched- thick straight hair
  (b) Smooth- thin straight hair
  (c) Flat or slightly wavy- waves having
  wave length between 5.5 and 6 cm. Such hair are found in the Mongoloids, Amerindians and Eskimos, Polynesians and Ainus.
• Cymotrichous: These can be categorized into
  (a) Broad wavy- having smaller radius varying from 3.5 to 4 cm.
  (b) Narrow wavy- short and strongly curved waves having wave length of about 2.5 cm.
  (c) Curly- broad spirals having waves in different planes. These types of hair are found among people from Western Asia, The Veddas of Sri Lanka, Australians, Indo-Afghans, Indonesians, Ethiopians and Europeans in general.
• Ulotrichous or Woolly Hair: These comprise frizly, pepper corn and spirals. These can be divided into five categories
  (a) Frizzly- irregular waves in different directions.
  (b) Loose frizzly- circular or flat spiral of about 1.5 cm in diameter.
  (c) Thick frizzly- circular and flat spirals having about 7-10 mm. diameter
  (d) Pepper Corn or Filfill This type has knots of thick rolled hair
  (e) Spiral This type consist of hair having very narrow spirals of thick twisted hair of small length.
  It is generally difficult to distinguish between the last two categories. Such types of hair are found among the Negroes, Andemanese, Bushmen, Papuans, Melanesians, Sudanese and Bantus. The curliest hair is found in the Khoisans whose hair is often so tightly curled that it is called peppercorn hair because it looks like pepper corns placed on their heads. Christiano et al. (2008) have recently demonstrated that mutations in a gene, known as P2RY5, cause hereditary “woolly hair”- hair that is coarse, dry, tightly curled and sparse. Incidentally, it is the first discovery of the new gene whose primary function seems to be the determination of hair texture in humans.

Hair Quantity

• Based on visual observations, hair quantity is denoted under three groups: scanty, medium and rich. Observations on head hair should be accompanied by those on body, beard and moustaches. Caucasians (Armenians & Georigians) and Arabs have extremely heavy body hair; Mongoloids have sparse body hair, beard and moustaches; while Negroid varies from sparse to intermediate position. Human head hair show a wide range of variation. So weight of hair is considered mor suitable criterion for racial classification. Hair weight should be determined after dehydration in a desiccator.

Hair Limit or Hair Slope
The anterior and posterior head hair limit on the forehead and nape of the neck is said to be genetically controlled. The frontal hair limit profiling is of two major types

• U form- resembles letter U,
• M form or V form-resembles letter
  M or the central cone or V at the centre of the forehead while two legs are seen in the parietal region. M-form usually occurs in male, while U-form in females. Hair slope on the nape is very much variable.

Hair Whorls

• A hair whorl on the occipital region of the head is universally observed in humans. Usually there is a single whorl, but at times there can be more than one whorl. Single hair whorl may be classified as clockwise or anticlockwise.

Morphological Characteristics of Eye

• A number of eye characteristics, like eye colour, eye opening and eye fold have been used in describing ethnic groups.

Eye colour

• It presents a striking range of variation. The coloured part of the eye is the iris, which surrounds the pupil of the eye and contains muscles which dilate and contract the pupil. The iris has several layers, two of which contain melanin. The variation in eye colour is caused by the nature of pigmentation and iris may or may not be pigmented. If melanin is present in the external layer of the iris then the eye will be brown. If melanin is lacking, the iris will be colourless but perceived as blue.
• If melanin is present but unevenly distributed the eye is perceived as a brownish green called as olive or hazel. True green eyes are extremely rare, a condition caused by presence of pigment in the external layer of the iris, carotene. The yellowish carotene combined with the blue of an unpigmented iris gives a green tinge. A progressive decrease in the amount of pigment yields a graded series of colours from brown to green and finally to grey and blue. Most people in the world have brown eyes, and non-brown eyes for hunters are advantageous against a snowy or light coloured background.

Eye Opening
According to anthropological literature eye opening has been examined from two major perspectives

• Height of the eye opening There are three major types- wide, medium and
  narrow.
• Eye Slant This can be straight or horizontal, laterally upwards or downwards.

Eye Fold
Fold of the skin hanging down over the upper eye lid have wide variations. The epicanthic fold does seem to offer some protection against snow blindness, caused by sunlight reflecting from snow. The following variations are generally observed

• Internal Epicanthic Fold The inner corner of the eyelid is covered over in this characteristic and this fold makes the inner corner of the lid curve downward.
• External Epicanthic Fold In this case, the fold hangs down over the outer canthus alone.
• Median Fold Margins of the upper lid that fall towards both canthi are exposed and the fold hangs over the middle part of the upper eye lid.
• Complete Mongoloid Fold This folds runs over the entire margin of the upper eye lid, covering both inner and outer canthi.
• Absence of Fold When there is absence of the upper four conditions.

Morphological Characteristics of Nose
Human nose differs in anatomy and morphology between racial groups. Anthropological literature has given a lot of emphasis on nasal variations among humans by taking a series of measurements of the nose and somatoscopy observations of shape of the nasal profile. Armenians and North American Indians have convex nasal bridge, Australians, Lapps, and Bushmen have concave nasal bridge. The following descriptive observations are made on the nasal morphology

• Nasal depression None, shallow, medium, deep.
• Nasal bridge Straight, concave, convex, concavo-convex or wavy.
• Nasal tip Sharp, medium, thick, bulbous.
• Nasal septum Sloping upward, sloping downwards, horizontal.
• Disposition of the nares High and narrow, medium broad, broad and flaring.

Nasal Index

• It is a ratio of nasal breadth to nasal length multiplied by one hundred. P. Paul Broca emphasised the importance of nasal index as the best indicator for ethnic description. Nasal shape is determined from the nasal index value as follows

• Anthropometric studies have shown that Negroes have a broad and short nose the Mongoloids have short and moderately broad (mesorrhine) nose. Australoids possess excessively platyrrhine nose. The Whites usually exhibit leptorrhine type of nose. Studies have shown that nasal proportions do vary between ethnic groups but the size and shape of the nose does not define precisely Caucasian, Mongoloids and Negroid races respectively.
• Anthropologists agree that the nasal variations are due to man’s adaptation to the environment. But recent published data on nasal physiology have not shown significant differences between the ethnic groups despite obvious differences in nasal proportions.

Morphological Characteristics of Lips

• Human lips are a peculiar trait that gives an enormous range of oral expressions brought by a complex set of muscles. Human lips are different from those of all other animals because they are everted. Everted lips seem to have a slight ability to help cool the body because capillaries run very close to the surface of the lips, and the slight moistness of the lips helps in cooling by evaporation. The most everted lips are found on the faces of Negroids and the least everted lips on the faces of some Europeans. On the basis of thickness of the lips, these can be divided into four categories: thin lips, medium lips, thick lips, very thick everted lips. African Negroes usually have the last type of lips.

Morphological Characteristics of Face

• Human face has many distinguishing characteristics that help in recognising them from each other. On the basis of conformation of the face, hair line, the form of the jaw and the forehead, the facial form is determined. Somatoscopy observations on forehead include height, slope, and width and brow ridges size.

Facial Form or Shape

• There are about ten facial types that have been reported: elliptic, oval, reverse oval, round, rectangular, quadratic, trapezium, inverted trapezium and pentagonal. The face usually harmonizes with the form of the head, so that a narrow face accompanies a narrow head. There are notable exceptions, however; for broad faces with long heads occur among sonic Eskimos. Facial form is determined with the help of facial index.
  Facial Index = Morphological facial height/ Bizygomatic breadth × 100
  This index is divided into five categories
  Studies have shown that Armenoids have a long and relatively narrow face. Mongoloids usually have broad face with prominent cheek bone.

Prognathism

• Projection of the face is an important criterion of the racial classification. The facial angle indicates that the angle made by the whole face with brain cap i.e. the angle between the horizontal line and the straight-line joining the centre of the chin and the fore head. If the facial angle is 90 it is called orthognathism. Facial prognathism occurs if this angle is less than 83, and between 83 and 90, it is known as mesognathism. Most of the white races are orthognathists, black races are prognathists and yellow races are mesognathists.

Morphological Characteristics of Head

The Cephalic Index

• The form of the head is ascertained by measuring in a horizontal plane the greatest length from a definite point on the forehead (the glabella) to the back of the head, and the greatest breadth a little above the ears. The cephalic index is an expression of the breadth of the head or skull in terms of percentage of the length. The difference of the index taken on the living and on the skull is about two units. The head form of skulls is called cranial index. Hence the cephalic index can be converted into the cranial index by the subtraction and vice versa. Formula for calculation of Cranial Index or cephalic index, C.I. = (Maximum Head breadth/Maximum Head length) ×100. Head shape has been arbitrarily classified, on the basis of cephalic index, into three categories as follows:
  

Morphological Characteristics of Ear

• Ears are classified depending on the ear’s length and breadth as long and narrow, as found in Mongols; short and wide, as found in Negroes, Negritos, Bushmen and Hottentots. Majority of the people belong to intermediate type. Europeans are the most variable and have ears that span the entire range of human variation. Longest and narrowest ears are found in Australoids, Mongoloids and some Whites. Ear lobe, which is another ear feature, can be free or attached. Europeans and Mongoloids have well developed ear lobes while Negroids have small free lobes. The attached ear lobe is found among Whites and Negroids.

Morphological Characteristics of Body Build

• Much variation in body build of humans can be reduced to linear build versus lateral build. Stature may be divided into three categories: short, medium and tall. The extreme linear stereotype is found among tall people of East Central Africa. The chest, shoulder, and hip are very narrow and limbs are extremely long. The extreme lateral stereotype would be found in Asian and Native Americans. Eskimos, Japanese, Samoans, Apache, and many South American Indians exhibit lateral build and a few Caucasoid people of northern Europe. Laterally built people tend to have long and broad trunk, with wider chest, shoulder and hip. The widest hips of all can be found in Europeans. The limb bones tend to be short and less contributed to overall
  height.

Genetic Criterion of Race

After the rediscovery of Mendelism, it was observed that inheritance of traits in human follow Mendelian laws. Morphological traits were found to be adaptive, and hence human taxonomists started using genetic traits to study variations among human populations. The gene frequencies at various polymorphic genetic loci were used to supplement definition of race from morphological characters. Rosenberg et al. (2002) have shown that individuals can be assigned to specific clusters with high degree of accuracy on the basis of human genetic diversity despite the fact that the majority of variation is found within populations. During the first half of the 20th Century, the following genetic markers were used to study differences among human races on the basis of their relative phenotypic frequencies.

Blood Groups

• The antigens that express on the red blood cell determine an individual’s blood group. On the basis of these antigens, a number of blood group systems have been identified.

ABO Blood Group System

• ABO blood group has four phenotypes (A, B, AB, and O). The genes for O and A are widespread among all groups of people on the globe, while B is the rarest allele. 16% of humanity has B allele and about 21% have the A allele and O blood type is very common and about 63% of humans share it. The highest frequencies of A are found in small, unrelated populations, especially the Blackfoot Indians of Montana (30-35%), the Australian Aborigines (many groups are 40-53%), and the Lapps, or Saami people, of Northern Scandinavia (50- 90%). 
• The A allele apparently was absent among Central and South American Indians. Type O is particularly high in frequency among the indigenous populations of Central and South America, where it approaches 100%. It is also relatively high among Australian Aborigines and in Western Europe (especially in populations with Celtic ancestors). The lowest frequency of O is found in Eastern Europe and Central Asia, where B is common. Blood type B is relatively common in Chinese and Indians in about 25% of the population whereas it is less common in European countries and Americans of European origin, being found in about 10%. Blood type AB is the least common.
• Considerable numbers of variants of the A antigen are known, most of which are rare; the B antigen is less varia le but several rare variants are known. There are over 20 recognised variants of group A- although about 95% of all A’s are A1. Most of the variants are found in Africa, and probably represent adaptations to local parasites. These include A2, A3 and A-Bantu. The highest frequencies of A2 are found in small, unrelated populations, especially the Blackfoot Indians of Montana (30-35%), the Australian Aborigines (many groups are 40-53%), and the Lapps, or Saami people, of Northern Scandinavia (50-90%).

Rh Blood Group System

• From the clinical point of view the Rhesus or Rh system is the most important system other than ABO. Rh D blood group has two phenotypes: Rh D positive (Rh+) or Rh D negative (Rh-). Studies have shown that most African populations are around 75% Rh+. Europeans have the lowest frequency of this blood type for any continent; Rh+ is around 60%. The lowest known frequency is found among the Basques of the Pyrenees Mountains between France and Spain where it is only 47% Rh+.
• The complexity of the Rh blood group antigens begins with the highly polymorphic genes that encode them. There are two genes, RHD and RHCE that are closely linked. Numerous genetic rearrangements between them have produced hybrid Rh genes that encode a myriad of distinct Rh antigens. To date, 49 Rh antigens are known. The most common Rh haplotype in Caucasians, Asian Mongoloids, and Native Americans is DCe.
  Frequency distribution of various Rh antigens among different races is as follows:
  D 85% Caucasians, 92% Blacks, 99% Asians
  C 68% Caucasians, 27% Blacks, 93% Asians
  E 29% Caucasians, 22% Blacks, 39% Asians
  c 80% Caucasians, 96% Blacks, 47% Asians
  e 98% Caucasians, 98% Blacks, 96% Asians
• Frequency distribution of various Rh haplotypes among different races is as follows: Rh haplotype DCe: most common in Caucasians (42%), Native Americans (44%), and Asian Mongoloids (70%); Rh haplotype Dce: most common in Blacks (44%); Rh D-negative phenotype: most common in Caucasians (15%), less common in Blacks (8%), and rare in Asian Mongoloids (1%).

MN Blood Group System

• The frequencies of the M and N genes of the MN system have been found to be closely similar up to 50 per cent. There are three phenotypes: M, N and MN with specific variations. Australians have low frequency of M blood group, while American Indians have low N blood group. MN blood group phenotype frequencies among Caucasians are: 0270 (MM), 0.540 (MN) and 0.189 (NN). S and s antigens were discovered in 1947 and 1951 for a model of closely linked genes, two closely linked loci for CE/D loci of Rh blood group system, one determining the alleles M and N and the other S and s under MNSs system. Thus there are four haplotypes: MS, Ms, NS, and Ns. Under this system many new antigens have been found, but the Henshaw or He antigen, has great anthropological value, for it appears to be totally limited to populations of African ancestry.

Duffy Blood Group System

• The Duffy blood group was discovered in 1950. The allelic genes Fya  and Fyb account for all the phenotypes under this system. The Duffy null phenotype, Fy(a-b-), is rare among Caucasian and Asian populations, a common phenotype in Blacks (2/3rds). Fy allele has a frequency of 0.03 in Caucasian populations and 0.939 in African Negro populations, while Mongoloids have a frequency of 0.0985. Frequency of Fya allele is 0.9015 in Mongoloids from China, 0.0607 in African Negroes and 0.42 in Caucasians. Frequency of the other allele Fyb  is 0 in Mongoloids from China, 0 in African Negroes and 0.5492 in Caucasians. The racial variation in the distribution of Duffy antigens is a result of a positive selection pressure, because the absence of Duffy antigens on RBCs makes the RBCs more resistant to invasion by a malarial parasite.
  Summary of blood group variations (in %) among human populations
  
• The blood group variation among humans provides a useful opportunity to examine definition of race in terms of gene frequencies in populations rather than in terms of the characteristics of an isolated individual.

Other Genetic Traits

Ear Wax

The consistency of ear-wax is found to be under genetic control. Cerumen (earwax) may be wet (sticky) or dry (hard); the types are controlled by a pair of allelic genes, that for the wet type expressing itself dominantly in relation to that of dry. The distribution of the alleles, showed that wide variations in gene frequencies throughout the world, the dry allele being predominant in the Mongoloid peoples; wet allele in Caucasoids and absent in Negroids. The percentage frequency of gene bearing dry wax in some populations is as follows:

• Mongoloids = 92-98%,
• Melanesians = 53%,
• Micronesians = 61%,
• Whites = 15 - 20%,
• Negroes= <10%.

PTC Tasters and Non-tasters

• The majority of people in any population can taste phenylthiocarbamide (PTC) bitter. The ability to taste these substances was shown by Blakeslee and Salmon (1931) and by Snyder (1932) to behave as a Mendelian dominant character. The lowest frequency of PTC non-tasters is seen among Australian aborigines (50 – 70%) and the highest among Mongoloids (83 -100%) and Negroids (90- 97%).

Amino acid Excretion in Urine

• Urine is an indicator of internal body chemistry. Since the simultaneous discovery by Crumpler et al. (1951) and by Fink et al. (1951) that a particular amino acid, Beta-aminoisobutyric acid (BAIB), may be excreted in large quantities in the urines of certain individuals. Several investigators have shown that this trait as characteristic of individuals and largely independent of environmental factors.
• For example, beta-amino-isobutyric acid (BIAB) is rarely excreted in large amounts by Europeans, while excess excretion is common in Mongoloids. Harris (1953) classified individuals as “excretors” or non-excretors” and found that the frequency of “excretors” was 9.6 per cent in the United Kingdom and suggested that the trait was under genetic control. Differences among races have been observed from the urine-analysis for subtle and non-pathological traits.

Dermatoglyphics

• Dermatoglyphic patterns of fingers, palms and soles have been extensively analysed to study racial variations. Dermatoglyphic patterns are present at birth and do not change throughout the remainder life. The patterns present on finger tips are loops, arches and whorls. The similarity of patterns of two individuals can be used as an index of similarity. The data in Table 3.2 shows preponderance of loops in Caucasoids and African populations, while Mongoloids have more whorls than loops.
  Frequency of Fingerprint patterns in different populations
  
• Pattern intensity index is the number of tri-radii present on finger ball patterns. Among Whites, Nordic subgroup shows low pattern intensity; while Mediterraneans show higher intensity and Alpines are characterised by intermediate value of the index. Arabs, Syrians, Indians and Jews have slightly higher pattern intensities than Europeans.