Visual Acuity and Color Blindness Among Brazilian Cayapo Indians

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Human Heredity 22: 72-79 (1972)

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Visual Acuity and Color Blindness Among Brazilian Cayapo Indians F. M. SALZANO Departamento de Genética, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, Pôrto Alegre

Abstract. Tests with lsHIHARA's plates [6] showed that only 1 of Key Words Color blindness 120 males belonging to two populations of Brazilian Cayapo Indians was color-blind (deuterodefective). This characteristic was not observisual acuity Brazilian Indians ved among 149 women. Visual acuity was tested in 149 persons; they generally presented excellent vision, more than half showing an acuity better than 20/20. These results are in accordance with the hypothesis that selection may have been important in preserving individuais with exceptionally good visual acuity and a low frequency of color-blinds among hunters and gatherers.

lntroduction

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Recently severa! papers have stressed the importance o f the study of colo r vision and visual acuity in an evolutionary context [2, 8, 10, 14, 15]. It was pointed out, for instance, that the much lower frequency of defective color vision in primitive as compared to civilized .peoples could be explained at least in part by a relaxation of selection against individuais with this condition in agricultura! as contrasted with hunting-and-gathering societies. NEEL and PosT [10] suggested in addition the possibility of a transitory 'positive' selection for color blindness during the transitional period when hunting and gathering was being replaced by agriculture and pastoralism . Color-blind individuais would have been among the first to turn to other pursuits besides hunting and since these would be less hazardous a positive selection could have resulted. They further pointed out that color blindness provides the only clear example of a simple inherited defect whose frequency seems to have significantly increased with the advent of civilization; therefore, a considerable effort should be directed toward the testing of the correctness of these and other hypotheses .

Visual Acuity and Color Blindness Among Brazilian Cayapo Indians

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The situation with regard to visual acuity is much less clear, because fewer populations living at different stages of cultural development have been subjected to study and also due to the fact that the relative importance of heredity and training is not well established in this characteristic. But the lower frequencies of vision defects among different samples of hunters or erstwhile hunters and the higher frequencies among populations with relatively long histories of agriculture and settled habits also suggest the occurrence of selection relaxation [15]. Despite this existing interest, not much is known about these conditions in South American Indians. I have been able to locate only 9 articles dealing with color blindness in these populations [3, 5, 7, 9, 11, 16, 17, 20, 21] and 3 with visual acuity [9, 11 , 21]. The present communication furnishes additional data about these characteristics in two populations of Brazilian Cayapo Indians; it is related to a series of other papers which h ave dealt with se1ected aspects of the hea1th, demography, morphology and genetic polymorphisms of these Indians [4, 12, 13, 18, 19, 22]. Materiais and Methods The subjects studied belong to two Cayapo subgroups, the Kuben-Kran-Kegn and Mekranoti. The former live near the Riosinho ri ver, an affluent of the Fresco (Iat. 8°10' S ; long. 52°8' W), numbering some 310 persons, while the Mekranoti are located in the Iriri river region (Iat. 8°40' W; long. 54° W) and have their popu1ation estimated as 260 individuais. Both o f these places are quite isolated and the lndians (especially the Mekranoti) have not been much disturbed in their traditional ways of life. They are still semi-nomad, most of the group leaving their semipermanent village for extended periods of time to hunt in the forest ; but they do practice some agriculture. Some 20 years ago they were still hostile to non-Indians. For further information see SALZANO [18). The color vision tests were performed with plates 26-38 of ISHIHARA's [6) book. These plates, designed for illiterate people, were shown to the subjects who in turn were instructed to follow the lines with a little brush. Mter performing the test with plate 38 (whose lines can be seen by ali persons) another was offered at random from plates 30--37. Mterwards the individual was asked to follow the !ines of plates 26 or 27. Plates 28 and 29 were also offered to the one color-blind person found . Visual acuity was tested with a Snellen Illiterate E Chart at 20ft, both eyes being tested simultaneously.

Results

Table I summarizes our results on color blindness. Tests were made with 120 males (27 Mekranoti and 93 Kuben-Kran-Kegn) ; ofthese, only one was color-blind (deuterodefective). This 36-year-old man also presented diver-

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Tab/e I. lncidence o f color blindness in two populations of Cayapo lndians compared with similar data from other South American Indian populations Population

Males Number studied

Mekranoti Kuben-Kran-Kegn Total Cayapo Xavante2 Caingang3 Severa! tribes4 Carajá5 Jivaro 6

27 93 120 172 301 205 35 183

F em ales Number and % defective

o p 11

o 73

2

o 2 13

6 7

Number studied

Numberand % defective

53 96 149 186 224 95

o o o o o o o o

o 144

1

Deuterodefective. NEEL et a/. [11]; WEINSTEIN et a/. (21]. 3 SALZANO [16, 17]; FERNANDES et a/. (5]; MATTOS (9]. 7 = 5 protodefective, 2 not diagnosed. 4 MATTOS (9]. 5 JuNQUEIRA et al. [7]. The two color-blind individuais were deuterodefective. 6 SUNDERLAND and RYMAN (20]. 2

gent strabismus. As expected, none of the 149 females studied presented defects. These results can be compared with those obtained in 5 other investigations, which included 896 men and 649 women. No color-blinds were observed among the latter. Among males those belonging to two other tribes (the Xavante and Caingang) who speak a Ge language as the Cayapo do, show widely divergent figures. Among the Xavante no defectives were found [11, 21], while 7 of the 301 Caingang tested were color-blind (5 protodefectives, 2 not diagnosed) [9, 16, 17]. There is also heterogeneity in the results reported in the three other studies. None of20S individuais belonging to severa! tribes tested by MATTOS [9] showed color blindness but defectives were observed among the Carajá and Jivaro [7, 20]. The results of CRUZCOKE and BARRERA [3] were not incorporated in the table beca use the Aymara speaking individuais studied included many Mestizos (7 of the 9 color-blinds found presented some non-Indian ancestry). lnformation about the visual acuity studies is given in table 11. A total of 194 individuais was studied (52 Mekranoti and 142 Kuben-Kran-Kegn). The differences between subgroups were insignificant. The Cayapo generally


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Table li. Visual acuity in two populations of Cayapo lndians compared with similar data from another Brazilian Indian tribe Populations and age range, years Mekranoti 0-14 15-30 31 and over

Sex

Number 20/70 tested

M F M F M F

4 13 7 14 6 8 52

Total %

Kaben-Kran-Kegn M 0-14 15-30 31 and over

F M F M F

15-30 31 and over Total %

Xavante [11, 21] Total % 1

o o o o o o o

o o o o o o o

o o o

o o o o o o o

p

o o

142

Total %

Total Cayapo 0-14

14 8 36 34 25 25

M F M F M F

20/50

194

o o o o o o o

301

3

18 21 43 48 31 33

o o o 11

o o

20/30

o o o o

20/20

4

20/15

3 6 4 8

20/10

o 3 2 2

2

4 3 4

3 6

17 33

23 44

o o o 5 7 5

3 3 7 10 8 16

9 5 21 18 7 2

17 12

47 33

62 44

15 10

o o o 5 9 6

4 7 8 14 11 20

12 11 25 26 8 3

2 3 10 2 3 4

20 10

64 33

85 44

24 12

28 9

65 22

131 44

73 24

o 2

This 30-year-old female lost one of her eyes in infancy, due to an accident.

9 17

2

o 8

o 3 2

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present excellent visual acuity (more than half of the individuais tested showed an acuity better than 20/20), which as expected showed some reduction with age. These figures are similar to those observed among the Xavante [11, 21]; however, in the data presented here the marked sexual difference in visual acuity observed among the latter was not apparent. Two other investigations dealing with the visual acuity of American Indians were not summarized in the table due to differences in methodology. MATTOS [9] studied 250 males and 143 females from severa! tribes, comparing their vision with those of Neo-Brazilians: 227 males and 192 females from Central Brazil, as well as 56 males and 44 females from São Paulo. Since he tested the two eyes separately, his results cannot be strictly compared with those presented here. He found significant heterogeneity between individuais from two groups of tribes, the Carajá, Cayapo, Caingang and Xingu Indians showing better vision than the Fulnio, Xavante, Guarani and Terena. There were also differences between the Neo-Brazilians, those from Central Brazil showing better vision. The Indians of the first group, who are in generalless acculturated than the other, always showed better vision when compared Table //la. Second test. Comparison oftests made on the same subject in the Kuben-KranKegn subgroup after an interval of 3 years

First test Males

Fe males

20/15

20/20

1 4

o

o o

o

o o

o

o

20/10 20/10 20/15 20/20 20/30 20/10 20/15 20/20 20/30 20/70

3

o o 1

o

2

o o o

1

o

1

o o o

20/30

5

3 2

o

o

o

20/50

o o o o o o o o

Table /1/b. Summary of the performance in the 2nd test

Equal Males F e males

Better

5

7

5

10

Worse

Total 13 16


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with Neo-Brazilians; in some of the comparisons, however, those of group 2 presented about the same degree of visual acuity as the Neo-Brazilians. On the other hand, ÁDAMS et al. [1] studied the visual acuity of 323 Papago children and adults using a Landolt ring test for far vision. Their acuity was notas good as the Cayapo and Xavante ones, only 25% ofthe sample showing vision better than 20/22 to 20/18. Their sample included more individuais under 15 years of age, but the sex distribution was about the same as that of the persons studied here. Among those under 30 years of age a difference between the sexes was apparent. Since I have visited the Kuben-Kran-Kegn two times, in 1965 and 1968, an opportunity arose to test the same individual more than once, with an interval of 3 years. A series of circumstances limited this type of observation to 13 males and 16 females. The results of these two examinations are presented in tables Illa and b. No differences among the sexes are apparent. About one third of the individuais showed an equal performance in the two tests. The majority, however, obtained better ratings at the second time, indicating the importance of familiarity with the test. Only two persons presented a worse result at the second examination: a mal e whose age was estimated as 48 years at the first test showed an acuity of 20/20 in 1965 and 20/30 in 1968; anda 47-year-old female, who obtained a 20/10 rating at the first time and a 20/20 value in 1968.

Discussion As was emphasized in the introduction, the color blindness polymorphism presents a series of features of great evolutionary interest. But care should be taken to avoid hasty conclusions. One important point concerns the proper identification of the condition. There is a defini te possibility that some of the forms seen in a given population are 'acquired' [2]. This may be true in relation to the only color-blind individual found among the Cayapo, since he showed another eye defect. On the other hand, it is well known that lsHIHARA's [6] plates detect only a fraction of the color-blinds present in a group; ideally, therefore, surveys should be conducted with portable anomaloscopes. The problem is that their use involve complex, time-consuming procedures plus the need for a skilled observer (for a discussion of this point see ref. 2). lt is still uncertain if South American Indians presented the color-blind genes in polymorphic frequencies before their contact with Europeans. The presence of these genes in some tribes may be due to admixture, but it is

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difficult to interpret their occurrence in all groups by postulating just this factor. In a general way, however, the results are in accordance with the hypotheses of selection relaxation or the 'positive' selection outlined before [10, 14], since South American hunters and gatherers with incipient agriculture seem to have lower frequencies of these genes. The results reported here confirm the excellent visual acuity observed in individuais from other South American Indian tribes living at a comparable stage of cultural development. They also do not contradict PosT's [15] hypothesis of selection relaxation concerning this characteristic; as a matter of fact, the duplicate observations made in the same individual among the Kuben-Kran-Kegn indicate that the vision ofthe Cayapo and Xavante may be even better than the results have suggested to date.

Acknowledgements Thanks are dueto F. J. DA RocHA and G. V. SIMõES for help in the field work and the Fundação Nacional do Índio who gave permission to study the lndians and provided ali facilities. Transportation to and from the villages was made possible by AsAs DE SocoRRO. This work is part of the Brazilian contribution to the International Biological Programme. Our researches are supported by the Conselho Nacional de Pesquisas, Conselho de Pesquisas da Universidade Federal do Rio Grande do Sul, Coordenação do Aperfeiçoamento do Pessoal de Nível Superior, Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul, and the Wenner-Gren Foundation for Anthropological Research.

References

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ADAMS, M. S.; BROWN, K. S.; lBA, B. Y., and NISWANDER, J. D.: Health of Papago lndian children. Publ. Hlth Rep., Wash. 85: 1047-1060 (1970). CRuz-coKE, R.: Color blindness. An evolutionary approach (Thomas, Springfield 1970). CRuz-CoKE, R. and BARRERA, R.: Color blindness among Aymara in Chile. Amer. J. phys. Anthrop. 31: 229-230 (1969). DA RocHA, F. J. and SALZANO, F. M.: Anthropometric studies in Brazilian Cayapo Indians. Amer. J. phys. Anthrop. (in press). FERNANDES, J.L.; ]UNQUEIRA, P.C.; KALMUS, H.; ÜTIENSOOSER, F.; PASQUALIN, R., and WISHART, P.: P. T. C. thresholds, colour vision and blood factors o f Brazilian lndians. I. Kaingangs. Ann. hum. Genet. 22: 16---21 (1957). ISHIHARA, S.: Tests for colour-blindness (Kanehara Shuppan, Tokyo 1957). JUNQUEIRA, P. C.; KALMUS, H., and WISHART, P.: P. T. C. thresholds, colour vision and blood factors of Brazilian lndians. 11. Carajas. Ann. hum. Genet. 22: 22-25 (1957).


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8 KALMUs, H.: Diagnosis and genetics of defective colour vision (Pergamon, Oxford 1965). 9 MATIOS, R. B.: Acuidade visual para longe e freqüência de discromatopsia em índios brasileiros. M. D. thesis, São Paulo (1958). 10 NEEL, J. V. and PosT, R. H.: Transitory' positive' selection for colorblindness? Eugen. Quart. 10: 33-35 (1963). 11 NEEL, J. V.; SALZANO, F. M.; JuNQUEIRA, P. C.; KEITER, F., and MAYBURY-LEwrs, D.: Studies on the Xavante lndians ofthe Brazilian Mato Grosso. Amer. J. hum. Genet. 16: 52-140 (1964). 12 NUTELS, N.; AYRES, M., and SALZANO, F. M.: Tuberculin reactions, x-ray and bacteriological studies in the Cayapo Indians of Brazil. Tubercle 48: 195-200 (1967). 13 PENA, H. F.; SALZANO, F. M., and DA RocHA, F. J.: Dermatoglyphics o f Brazilian Cayapo Indians. Human Biol. (in press). 14 PosT, R. H.: Population differences in red and green color vision deficiency. A review, and a query on selection relaxation. Eugen. Quart. 9: 131-146 (1962). 15 PosT, R. H.: Population differences in vision acuity. A review, with speculative notes on selection relaxation. Eugen. Quart. 9: 189- 212 (1962). 16 SALZANO, F.M.: Rare genetic conditions among the Caingang Indians. Ann. hum. Genet. 25: 123-130 (1961). 17 SALZANO, F.M.: Color blindness among Indians from Santa Catarina, Brazil. Acta genet., Basel14: 212- 219 (1964). 18 SALZANO, F. M.: Demographic and genetic interrelationships among the Cayapo Indians of Brazil. Soe. Biol. 18: 148-157 (1971). 19 SALzANo, F.M.; GERSHowrTz, H.; JuNQUEIRA, P.C.; WoooALL, J.P.; BLACK, F. L., and HIERHOLZER, W.: Blood groups and H-Lea salivary secretion of Brazilian Cayapo Indians. Amer. J. phys. Anthrop. (in press). 20 SUNDERLAND, E. and RYMAN, R.: P. T. C. thresholds, blood factors, colour vision and fingerprints of Jivaro Indians in Eastern Ecuador. Amer. J. phys. Anthrop. 28: 339-344 (1968). 21 WEINSTEIN, E.D.; NEEL, J. V., and SALZANO, F. M.: Further studies on the Xavante Indians. VI. The physical status of the Xavantes of Simões Lopes. Amer. J. hum. Genet. 19: 532-542 (1967). 22 WEITKAMP, L.R.; NEEL, J.V.; SALZANO, F.M., and WooDALL, J.P.: Serum proteins, hemoglobins and erythrocyte enzymes of Brazilian Cayapo Indians (in preparation).

Author's address: Dr. F. M. SALZANO, Departamento de Genética, Instituto de Biociências, Caixa Postal 1953, 90000 Pôrto Alegre, Rio Grande do Sul (Brazil)