Abstract. In order to study the effects of consanguinity on IQ, a survey was conducted among the Ansari Muslims of Bhagalpur residing in suburban and rural ...
Behavior Genetics, Vol. 18, No. 5, 1988
Consequences of Consanguinity on Cognitive Behavior M o h a m m a d A f z a l 1'2
Received 6 Sept. 1985--Final 19 Jan. 1988
In order to study the effects of consanguinity on IQ, a survey was conducted among the Ansari Muslims of Bhagalpur residing in suburban and rural areas. Both outbred (N = 390from suburban areas and N = 358 from rural areas) and inbred (N' s = 300 and 266, respectively) children aged 9 to 12 years from socioeconomically middle-class families were administered the Weschler Intelligence Scale for Children--Revised [WISC(R)-74]. The coefficient of inbreeding, F, was .0625. The inbred children showed lower verbal (20 and22%) and performance (30 and20%) subtest scores and lower verbal (11 and 11%), performance (17 and 12%), and full-scale (15 and 12%) IQs. A three-factor analysis of variance performed on the full-scale IQ scores indicated that both consanguinity and locality affect IQ. The interaction between these two factors was also significant. Neither age nor sex affected these scores. Overall, subjects' performance scores were lower than verbal scores. KEY WORDS: consanguinity; inbreeding; IQ; Weschler Intelligence Scale for Children--
Revised [WISC(R)-74];rural-suburban; Ansari Muslims. INTRODUCTION Studies dealing with the effects of consanguinity on IQ have been undertaken both in India and abroad (B66k, 1957; Slatis and Hoene, 1961; C o h e n et al., 1963; Schull and Neel, 1965; Bashi, 1977; Puri et al., 1978). These studies vary in methodology, scale used to assess IQ, type of popFinancial assistance received from the Council of Scientific and Industrial Research [Sanction No. 38(241)/80/EMR-II], New Delhi, is gratefully acknowledged. 1 Genetics Laboratory, Post-Graduate Department of Zoology, Bhagulpur University, Bhagalpur 812 007, India. 2 Present address: ZoologyDepartment, Aligarh Muslim University, Aligarh 202 001, India. 583 0001-8244/88/0900-0583506.00/09 1988PlenumPublishingCorporation
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ulation studied, and sample size. While most of these studies have shown some IQ-decreasing effect of inbreeding, some studies (Neel et al., 1970; Schull and Neel, 1972; Inbaraj and Rao, 1978) have not yielded any significant effects. Unfortunately, there are few studies that investigate individual subtests or that have large samples with varied age groups and gender. The present study, an investigation of the effects of consanguinity on IQ among Bihari (Indian) Muslims, sought to overcome these limitations. METHODS
Sample (Table I). The population of Bihar (India) is only 13.5% Muslim; however, three cities of Bihar, namely, Bihar Shariff, Darbhanga, and Bhagalpur, have higher proportions of Muslims, 35.8, 25.4, and 30.0%, respectively (Muslim India, 1983). The present study was conducted in Bhagalpur. The Muslims of Bhagalpur are predominantly Sunnis, although some are Shias and Ahmadiyas. Among the Sunnis, only about one-fourth belong to the socially higher caste, the Ashraffs (Hunter, 1870). Foremost among the lower castes are the Anaris (Roy-Chaudhary, 1962). The subjects of the present study were Ansaris.
Table I.
Subjects Available for IQ Study a Suburban
Nonconsan.
Rural
Consan.
Nonconsan.
Consan.
N
%
N
%
N
%
N
%
1. Total No. of married women 2. W o m e n i n t h e a g e group 30-36 years
5481
--
1728
--
2718
--
1806
--
825
15.0
245
14.2
405
14.9
252
13.9
1. No. of children of first two parity orders 2. Children d i d n o t a t t e n d school 3. Sick 4. Guardian did not permit 5. Children eligible for survey 6. Children actually surveyed
1606
--
478
--
798
--
496
--
398 24.7 120 23
7.4 1.4
120 25.1 25 7
295 36.9
5.2 1.4
30 10
3.7 1.2
1065 66.3
326 68.2
463
58.0
390 36.6
300 92.0
358 77.3
a Nonconsan., nonconsanguineous; consan., consanguineous.
162 34.4 26 6
5.2 1.2
302 60.9 266
88.0
Consequences of Consanguinity on Cognitive Behavior
585
Ansaris of Bhagalpus are primarily weavers (Momins). They are mostly neoconverts from the local Hindu population of lower rung, Julahas (Afzal, 1984). Recently the Ansaris' circumstances have improved with the introduction of power looms, weavers' cooperative societies, and commercial banks. They are highly religious, although without fanaticism, having high scriptural education and belonging to the Wahabi school of thought. The population is concentrated at six places, namely, Nathnagar, Champanagar, and Khanzerpur, which are all suburban, and Puraini, Khaira, and Katoria, which are rural. They are governed by a central Panchayat of a socioreligious nature, framed and imposed voluntarily. Subjects in the present study were from these six geographical areas. Subjects were contacted through a door-to-door survey. Parents aged 30 to 36 years with normal intelligence (as evidenced by their work skills) were selected. If their oldest child was aged 9 to 12 years, whether the marriage was consanguineous was noted, and for consanguineous couples, the coefficient of inbreeding was calculated. Only inbred children with a coefficient of inbreeding of .0625 were selected because other types of consanguinity were infrequent (10-20% of total consanguineous marriages). Children of consanguineous parents who themselves were the product of consanguinity were excluded, as they formed some sort of inbred line. Children from nonconsanguineous marriages served as a comparison group. No two children from the same parents were included. Only first- and second-born children were selected. Those having prolonged illness or suffering from congenital defects were excluded. These eliminations resulted in 463 outbred and 302 inbred children from rural regions and 1065 outbred and 326 inbred children from suburban regions. Of these available subjects, 358 outbred and 266 inbred children from rural regions and 390 outbred and 300 inbred children from suburban regions were tested. These samples correspond to about 77, 88, 37, and 90% of the available children. The subjects were selected randomly. Assessment Procedures. The verbal tests were translated from English into Urdu by the author, with two slight alterations in cultural reference, one each in the information and comprehension subtests. The subjects were approached through their parents and their name, age, sex, class, and school attended, along with parental consanguinity, were entered in the Weschler Intelligence Scale for Children--Revised [WISC(R)74] record form. The subject was then asked questions from the questionnaire as per instructions given in the manual and their answers were recorded on the schedule. Each subject was tested separately in one sitting which lasted approximately 1 hr, depending upon the intelligence and/or
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cooperation of the subject. Timing was noted with a stopwatch. Thirteen scores were recorded for each subject: 5 verbal scores, 5 performance scores, and 3 IQ scores. RESULTS
The full-scale intelligence quotient (IQ) scores of the entire sample are shown in Table II. Children born from both consanguineous and nonconsanguineous marriages among Ansaris show a normal distribution of scores. The scores range from 40 to 140. The mean IQ of the suburban sample was 92.3 _ 1.0 and 78.6 _ 0.9 for outbred and inbred children, respectively. Similarly, these values for the rural sample were 77.2 +__0.8 and 68.2 _+ 0.8. Overall, children from consanguineous marriages had lower scores (p < .001). This difference was also evident in the modal scores, which were 95 for suburban and 75 for rural outbred children, in constrast to 75 and 65, respectively, for the inbred children. It was expectable that the suburban sample would score higher than the rural sample. Gender did not appear to influence IQ in any of the samples. As mentioned earlier, the subjects were 9 to 12 years of age. A frequency distribution of IQ scores broken down by age is shown in Table III. The mean IQ for different age groups within the four samples did not differ. However, as expected, the range narrowed with increases in age. The total IQ scores discussed above were derived from the verbal IQ and performance IQ based, respectively, on five verbal subtests (Table IV) and five performance subtests (Table V). To investigate whether con-
Table II.
Frequency Distribution of Children for Their Full-Scale IQ Suburban
Rural
Class interval (IQ score)
Outbred
Inbred
Outbred
Inbred
40-49 50-59 60-69 70-79 80-89 90-99 100-109 110-119 120-129 130-140 T._otal (N) X • SE SD ( •
8 22 32 48 59 81 54 44 40 2 390 92.3 • 1.0 20.6
10 34 44 90 43 39 29 11 --300 78.6 • .9 16.8
13 34 62 127 45 54 18 11 4 -358 77.2 • .8 16.1
21 53 87 51 33 20 1 ---266 68.2 • .8 13.2
Consequences of Consanguinity on Cognitive Behavior
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