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Color blindness among Aymara in Chile.

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BRIEF COMMUNICATION
Color Blindness among Aymara in Chile’
R. CRUZ-COKE AND R. BARRERA
Deparhnent of Medical Genetics, Hospital J. J. Aguirre, and Department
of Genetics, School of Medicine, University of Chile, Santiago, Chile
ABSTRACT
Nine color blind subjects were discovered in a survey of 140 Aymaras
of Arica, Chile, using as screening test a portable Anomaloscope, Ishihara tables and
Hardy-Rand-Ritter plates. Pseudosisochromatic test failed on detecting four anomalous
trichrornates. Seven color blind subjects revealed foreign ancestors. Also a different
prevalence of defectives among subsamples was observed. Thus color blindness variability within the sample could be explained by gene flow. It is proposed to use
anomaloscopes as a screening device in order to survey with accuracy color vision genes
in human populations.
In two recent papers published in this
Journal (Adam, Doron and Modan, ’67 and
Adam, ’68) the authors stressed the necessity to survey color vision in primitive
populations with anomaloscopes, in order
to detect with accuracy the different phenotypes of color blindness. This proposition
is also supported by the human biologists
of the International Biological Programme
(Baker and Weiner, ’66).
We have reported a complete demographic, medical and genetic survey of
the Aymara speaking peoples living in the
Andrean regions of Arica, in northern
Chile (Cruz-Coke et al., ’66, ’67). In a
preliminary survey, using Ishihara and
H-R-R plates we were able to find a
gradient of increasing color blindness
from its absence in most primitive populations in the Sierra and Altiplano, down
to moderate frequencies in suburban
valleys near the port of Africa on the
Pacific Ocean (Cruz-Coke, ’66, Cruz-Coke
and Varela, ’66). Now we report the results of a new survey, using as a screening
device, a portable anomaloscope Nagel
type I (Schmidt and Haensch).
We examined all the population aged
10 years and older, who inhabited the
villages of Sobraya (coastal lowland valley
near Arica), Chapiquifia (Sierra at 3.300
meters) and Huallatire (Highland plateau
of Lauca at 4.500 meters). A small group
of 25 subjects from the far distant village
of Caquena, in the frontier with Bolivia,
were included in our total sample of 146
males and 139 females.
Every subject was examined under a
Mcbeth “daylight” Lamp with the Ishihara
AM. J. PHYs. ANTHROP.,31: 229-230.
tables (’64) and the Hardy Rand Ritter
(AO, ’57) plates. We also tested all the
sample with a portable anomaloscope
Nagel type 1. The Rayleigh equation was
tested thrice in one eye, and a mean redgreen mixture value to the nearest integer
was noted. Trichromate and Dichromate
defects were explored carefully along the
spectrum locus and the luminance yellow
in every testee.
From a total sample of 285 subjects,
sixteen of them ( 6 males and 10 females >,
with a normal testing of plates, were
unable to perform the anomaloscope testing-twelve
were schoolchildren, and
four, illiterate adults. All these subjects,
but three, lived in the altiplano.
The anomaloscope was able to detect
nine color blind subjects in the 140 remaining males examined (6.42% ) : two
protanomals, three deuter anomals, one
protanope and three deuteranopes. The
mean red-green mixture value for the 131
normal trichromates was 43.31 with a
standard deviation of 1.67, within the
normal range of the Anomaly quotient.
According to the expected frequencies of
the ratio q : qa not one color blind female
was observed. The plates of the Ishihara
and the H-R-R failed to detect two protanomals and two deuteranomals, a n omission error of 44% in the sample.
The table shows the distribution of the
defectives by geographical regions and
type of defect. The nine color blind subjects were unrelated and sporadic cases.
Two were born in southern Chile. Five
1 Supported by World Health Organization Grant
H.Q. W.H.O. 525/2.
229
230
R. CRUZ-COKE AND R. BARRERA
TABLE 1
Distribution o f defectives by geographical region altd type o f defect
Geographical
regions
Sobraya
Chapiquifia
Lauca
Male
53
47
26
Protan
Deutan
anomaly
anouia
anomalv
anonia
1
1
0
0
2
1
1
0
0
0
0
Total
51
1
0'
-
-
-
-
-
0
-
Arica gradient
12s
1
1
2
2
6
Caquena group
14
__
0
-
-
-
140
1
-
-
Total sample
3
3
9
1
2
2
1
1
1
3
No significant difference.
Mainly Bolivian sporadic travellers from Caquena, a frontier village with a population of 250.
out of seven natives on the region, traced
foreign ancestors from Bolivia, Peru,
Spain and southern Chile. Only two individuals, a deuteranomal of Sobraya
and a protanomal from Chapiquiiia, had
full native parents and grandparents.
Thus the existence of color blindness in
this sample can be explained by a significant gene flow from immigrants. Our
previous study, using the ABO system as
marker genes, have showed that the cumulated Caucasian admixture of this
Aymara speaking population was 13%
( m = 0.13) (Cruz-Coke et al., '67).
According with the results of our investigation we think that the study of
color vision variability among human
populations must be reviewed, using the
anomaloscope as a screening device. Certainly it is a complex and time consuming
method which needs a skilled observer,
but it is the sole possibility to obtain a n
accurate data on the color vision structure of mankind. This need is more urgent
if we consider that now, with the recent
discoveries of the two blue and two green
normal mutant (B1,Bz, GI and Gz) by
Waaler ('67, ' 6 8 ) , the number of the color
vision genes (cvp, cvP, cvd, cvD, cvt, and
cvT) have mounted up to 10. If we are
interested in applying evolutionary hypotheses to explain the origin and nature
of color vision polymorphism, a systematic
survey with anomaloscopes on the world
population, must begin without delay.
LITERATURE CITED
Adam, A. D., D. Doron and R. Moran 1967
Frequencies of protan and deutan alleles in
some Israeli communities and a note on the
selection-relaxation hypothesis. Am. J. Phys.
Anthrop., 26: 287-306.
Adam, A. 1968 Anomals and anopes among
Bedouin of Southern Sinai. Am. J. Phys.
Anthrop., 28: 227.
Baker, P. T., and J. S. Weiner 1966 The Biology of Human Adaptability. Oxford University
Press.
Cruz-Coke, R. 1966 Asociaci6n entre la oportunidad para la selecci6n natural, 10s defectos
de visi6n de colores y el alcoholismo crbnico
en diversas poblaciones humanas. Arch. Biol.
Med. Exper., 3: 21-26.
Cruz-Coke, R., A. P. Cristoffanini, M. Aspillaga
and F. Biancani 1966 Evolutionary forces
in human populations i n an environmental
gradient in Arica, Chile. Human Biology, 38:
421438.
Cruz-Coke, R., A. P. Critoffanini, E. Barrera and
A. Montenegro, A. 1967 Flujo genetic0 del
sistema ABO e n la poblacion de Arica. Rev.
Med. Chile, 95: 614-618.
Cruz-Coke, R., and A. Varela 1966 Inheritance
of alcoholism; its relation with color blindness.
Lancet, 2: 1282-1284.
Waaler, G . H. M. 1967 Heredity of two types
of normal coIor vision. Nature, London, 215:
406.
1968 Heredity of two normal types of
color vision. Nature, London, 218: 688-689.
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