ANNALS OF HUMANBIOLOGY, 1978, VOL. 5, NO.

2,

159-163

The incidence of colour-blindness among the tribal populations of Andhra Pradesh

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J. M. N A I D U and V. R. BABU Department of Human Genetics and Physical Anthropology, Andhra University, Waltair, India and P. V E E R R A J U Department of Anthropology, Andhra University, Waltair, India. [Received 19 November 1976; revised 15 August 1977] Summary. Among 126 Valmiki, 128 Bagatha, 129 Konda Dora and 73 Samanta tribals of Andhra Pradesh, the incidence of red-green colour-blindness in the males ranges from zero to "2.27 per cent. Samanta males exhibit no colour-blindness. In the females, only Konda Doras exhibit a frequency of 2.44 per cent of the trait. Comparison of the present data with the other available tribal and non-tribal data of Andhra Pradesh shows that our results fall well in the range for other data. Post's (1962) hypothesis of relaxation of selection against colour-blindness is also supported by our Andhra Pradesh data. 1.

Introduction

Population variation in sex-linked defective colour-vision has long been known. We report here a survey of the incidence of red-green colour-blindness among four tribal populations of Andhra Pradesh, namely Valmikis, Bagathas, Konda Doras and Samantas. 2.

Materials and methods

The present investigation was carried out in Paderu block of Visakhapatnam district of Andhra Pradesb. The sample includes 126 Valmikis (male, 57; female, 69), 128 Bagathas (male, 93; female, 35) 129 Konda Doras (male, 88; female, 41) and 73 Samantas (male, 31 ; female, 42). Only unrelated subjects aged 18-70 years were tested in the survey. Ishihara (1960) plates numbered from 1 to 24 for colour-blindness were used to test the subjects in indirect sunlight. 3.

Results and discussion

The sex-wise frequency of colour-blindness with its subclassification in the pooled sample of all the tribes namely Valmikis, Bagathas, Konda Doras and Samantas is listed in table 1. The males and females show the frequencies of the trait to be 1"49 and 0.53 per cent respectively. The subclassification of the five affected individuals reveal two protanope and two deuteranope males and a single protanope female. An attempt has been made to compare our data with the data from different Andhra tribal populations previously surveyed. Table 2 gives the incidence of colourblindness in 52 male samples, 27 female samples and 1 mixed sample drawn from

J . M . Naidu et al.

160

different populations of Andhra Pradesh. Out of the 52 male samples, 25 samples come from tribal series and 27 from non-tribal series, while among the 27 female samples, 16 samples are from tribal series and 11 from non-tribal series. Our results fall well within the range for other data. Of all the 25 tribal male series, Konda Kammara (Andhra University reports, 1977) record the maximum frequency of colour-blindness as 6.80 per cent.

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Colour-blind Sex Male Female Both sexes

Protans*

Deutans*

Protanope

Deuteranope

Number tested

No.

~

No.

~

No.

269 187 456

4 1 5

1.4869 0. 5347 1.0965

2 1 3

0. 7435 0. 5347 0. 6579

2 0 2

0.7435 0-0 0.4386

* No Protanomalous and Deuteranomalous cases were observed in the present study. Table. 1 Incidence of colour-blindness among Andhra tribal populations.

Relaxation of natural selection According to Post (1962), it is expected that there will be high prevalence of colour-blindness incidence among the populations belonging to pastoral-agricultural economies or settled habitat and low incidence rate in the hunter and food gatherer groups due to the effect of relaxed selection. But Indian populations so far tested include only "pastoral or agricultural economics" or "settled" or "protected" habitat groups. Practically none of the "wild" or "natural" or "hunter-food gatherer" groups is represented. Virtually all the tribals practise agriculture and secondarily, hunting. Nevertheless, in order to study the selective mechanisms, the populations belonging to the "culturally advanced" society and the "primitive tribals" can be t a k e n into account (Dutta, 1966). An attempt has been made to test the validity of Post's hypothesis (1962) of relaxed selection against colour-blindness, by categorizing the available data of Andhra Pradesh populations into sex-wise distribution of "advanced non-tribal" and "primitive tribal" series and by pooling the results of all the samples so far investigated (table 3). The "primitive tribal" category people having their primitive cultural background have reported the overall lowest mean prevalence rates of 0.0231, 0.0011 and 0.0163 defective colour-vision in males series, female series and both sexes series respectively. It may be thought that life would be handicapped with such a condition, and the low prevalence may, for one reason, be due to the result of the high degree of selection pressure, whereas the culturally advanced people, the "advanced non-tribal" series, have exhibited the overall higher prevalence rates of 0.0431, 0.0076 and 0.0372 in male series, female series and both sexes series respectively, which may, at least in part, be due to the low degree of selection pressure. If these two divisions are compared, it appears that the higher prevalence rates of the advanced non-tribals might have been caused by the effect of relaxed selection against colourblindness. The differential rates between them~are statistically highly significant. This prevalence rate difference can be considered as evidence in support of Post's (1962) hypothesis of selection relaxation. However, some investigators such as Adam, Doron and Modan (1967) and Adam (1968).question the validity of testing the hypothesis of selection and relaxation on the .data based on Ishihara charts. Adam

Colour-blindness a m o n g A n d h r a Pradesh tribals Colourblind

Population School Children (NT) (Rayalaseema) [1 ] Sudras (N.T) [2]

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Brahmins (N.T) [2] Konda Reddis (t) [3] Konda Rajus (t) [3] Koya Doras (t) [3] Koya Kammaras (t) [3] Sugalis (t) [3] Pandavanayakas (t) [3] School Boys (N.T.) [3] Brahmins (N.T.) [4] Kshatriyas (N.T.) [4] Vysyas (N.T.) [41 Kapus (N.T.) [4] Kammas (N.T.) [4] Chettibalijas (N.T.) [4] Other Sudras (N.T.) [4] Harijans (N.T.) [41 Christians (N.T) [4] Muslims (N.T) [4] Konda Reddis (t) [5] Koya Doras (t) [5] Bagathas (t) (Chinthapalli) [6] Valmikis (t) (Chinthapalli) [6] Chencbus (t) [7] Gonds (t) [8] Bagathas (t) (Chinthapalli) [9] Valmikis (t) (Chinthapalli) [91 Konda Reddis (t) [10]

No. Sex tested No.

Colourblind

~

Population Brahmins (N.T) [11] Reddys (N.T) [11] Kammas (N.T) [11] Velamas (N.T.) [11] B.C (N.T) [11] S.C. (N.T) [11] Kshatriyas (N.T.) [11] Muslims (N.T.) [11] Christians (N.T.) [11] Jalaries (N.T.) [12] School Children (N.T.) [12] College Boys (N.T.) [13] Jathapus (t) [13]

-M F M F M M M M M M M M F M M F M F M M M F M F M F M M F M

536 180 112 83 122 61 6 966 44 51 24 277 122 70 13 35 10 171 48 33 44 121 27 47 12 18 17 13 170 147 216

22 16 0 5 1 0 1 25 2 1 0 15 9 0 3 I 0 8 0 3 5 9 0 1 0 1 0 2 5 0 4

4.10 8.89 0.0 6.02 0.82 0.0 16.66 2.59 4.54 1.96 0.0 5.41 7.38 0.0 23.07 2.86 0.0 4.68 0.0 9.09 11.36 7.44 0.0 2.13 0.0 5.55 0-0 15.38 2.94 0.0 1.85

F

100

0

0.0

Rellis (S.C.) [18]

F M M

110 94 77

0 1 5

0.0 1.06 6,49

M

114

Valmikis (t) (Paderu) [19] Bagathus (t) (Paderu) [19] Konda Doras (t) [19]

M M F

130 336 352

1 5 1 0

0.88 3.85 0.30 0.0

161

Savaras (t) [131 People of Visakhapatnam (N.T.) [14] Bagathas (t) (Paderu) [15] Valmikis (t) (Paderu) [15] Gadabas (t) [15] Bagathas (t) (Araku) [161 Konda Kammara (t) [17] Koya Dora (t) [17]

Samantas (t) [19]

No. Sex tested No. M M M M M M M M M M M F

396 101 78 78 163 112 98 419 45 325 131 118

18 2 4 1 9 1 2 10 1 8 6 3

4.54 1.98 5.13 1.28 5.52 0.89 2.04 2.38 2.22 2.46 4.58 2.54

M M F M F

503 78 84 98 77

24 0 0 2 0

4.77 0-0 0.0 2.04 0.0

M F M F M F M F M F M F M F M F M F M F M F M F

169 151 120 85 116 80 117 75 260 220 103 105 75 78 115 100 57 69 93 35 88 41 31 42

5 2 1 1 2 0 1 0 4 0 7 0 1 0 2 0 1 0 1 0 2 1 0 0

2.96 1-32 0.83 1.18 1.72 0.0 0.85 0.00 1.54 0.0 6.80 0.00 1.33 0.00 1.74 0.0 1.75 0-0 1.07 0-0 2.27 2.44 0.0 0.0

Key t; Tribe; N.T: Non-Tribe; S.C: Scheduled Castes; B.C: Backward (Class) Castes; M: M ale; F: Female. Sources of data [1] Ramachandriah (1960) [2] Dronamraju and Meerakhan (1961) [3] Dronamraju and Meerakhan (1963) [41 Chakravartti et al. (1971) [5] Andhra University Reports (1971) [61 Andhra University Reports (1972) [71 Ramana Rao et al. (1972) [8] Ramana Rao et al. (1973) [9] Venkateswara Rao and Reddy (1973) [10] Veerraju (1973) Table 2.

[11] [12] [13] [14] [15] [16] [17] [181 [19]

Murty and Vijayalaxmi (1974) Andhra University Reports (1974) Andhra University Reports (1975) Busi and Rao (1976) Andhra University Reports (1976) Reddy (1976) Andhra University Reports (1977) Naidu and Mathews (1977) Present study

Incidence of colour-blindness in different Andhra populations.

162

J . M . Naidu et al. Defective colour vision Sex

Cultural division

Advanced Non-Tribal Primitive Tribal Advanced Non-Tribal Female Primitive Tribal *Advanced Non-Tribal Both sexes Primitive Tribal Ann Hum Biol Downloaded from informahealthcare.com by Chulalongkorn University on 12/30/14 For personal use only.

Male

Sample size

Number

Prevalence rate

3890 3525 787 1700 5213 5225

171 73 6 2 199 75

0.0440 0.0207 0.0076 0.0012 0.0382 0-0114

X2 1 d.f.

~

(

'1 f 'l f

f ~ f ~_

31.4110 P < 0.001 6. 9743 0.01 >P>0.001 57.9252 P

The incidence of colour-blindness among the tribal populations of Andhra Pradesh.

ANNALS OF HUMANBIOLOGY, 1978, VOL. 5, NO. 2, 159-163 The incidence of colour-blindness among the tribal populations of Andhra Pradesh Ann Hum Biol...
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