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Inbreeding and reproductiveparameters amongMennonites in KansasMary Jane Moore aa Department of Anthropology , San Diego StateUniversity , San Diego, CaliforniaPublished online: 23 Aug 2010.

To cite this article: Mary Jane Moore (1987) Inbreeding and reproductiveparameters among Mennonites in Kansas, Biodemography and Social Biology,34:3-4, 180-186, DOI: 10.1080/19485565.1987.9988674

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Inbreeding and Reproductive ParametersAmong Mennonites in Kansas

Mary Jane Moore

Department of AnthropologySan Diego State UniversitySan Diego, California

ABSTRACT: The relationship between inbreeding and certain reproductive parameters wasstudied by analyzing the reproductive history questionnaires collected from 194 women whoattended a research clinic in the Mennonite community of Goessel, Kansas, and for whompedigrees were constructed from data at the Mennonite Historical Library and at theAlexanderwohl Church. Five reproductive parameters, age of menarche, age of menopause,length of reproductive span, number of children, and fetal wastage, were compared in inbredand noninbred women. There is no consistent evidence that absence of inbreeding or degree ofinbreeding (F = 0.00024—0.0332) significantly affects these reproductive parameters in thissample of Mennonite women. If inbreeding does have an effect on these reproductive variables,it is too small to be detected in this sample.

Inbreeding depression in domesticand experimental animals has long beenknown to result from the mating of bio-logically related individuals. Falconer(1960) in his discussion of inbreeding de-pression states that the reduction inmean phenotypic values with inbreedingis greatest for traits that are associatedwith reproductive fitness. Thus, charac-ters such as litter size or lactation inmammals are more strongly affectedthan those such as bristle number inDrosophila, which shows little or nochange.

The effects of inbreeding in humanpopulations have been a topic of re-search for many years. Most publishedstudies have been concerned only withthe consequences of inbreeding in thefetus, i.e., the offspring of parental con-sanguinity. But one can also study pa-rental inbreeding by seeing if reproduc-tive parameters of the individual areaffected by his or her own degree of in-breeding. In this paper the parametersof age of menarche, age of menopause,

reproductive span, number of livingchildren, and fetal deaths will be exam-ined in relation to degree of inbreedingin women of the Mennonite communityof Goessel, Kansas. These data are partof a large multidisciplinary study on ag-ing carried out at the University of Kan-sas.

MATERIALS AND METHODS

MENNONITE POPULATION

The Mennonite community of Goes-sel traces its historical origins to the Pr-zechowka Church in West Prussia in1669. The members kept very good re-cords which documented the popula-tion's growth and eventual migration toRussia in 1821. There, the congrega-tion's name was changed to Alexan-derwohl in honor of the Czar. Later, in1874, political and economic conditionsin Russia led the population to move tothe United States. Once in the UnitedStates, the group partitioned into threeparts. The group that settled in Goessel

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Vol. 34, No. 3-4 Mennonites in Kansas 181

(40 miles north of Wichita) becameknown as the "New Alexanderwohl"congregation. The AlexanderwohlChurch underwent fissioning in 1909and 1920, when two daughter congrega-tions formed. This study focuses on theNew Alexanderwohl Church and itsdaughter congregations—the GoesselMennonite Church and the Tabor Men-nonite Church. All of these congrega-tions are members of the General Con-ference of Mennonite Churches. Moredetails of Alexanderwohl history can befound in Crawford and Rogers (1982).

The Goessel community is a stable,homogeneous population living in a rel-atively low-stress environment. Mem-bers of this population share a commonreligion, history, and form of subsis-tence, farming. Thus, the rich historicalrecord and homogeneous socioeco-nomic conditions make Goessel an idealpopulation in which to compare repro-ductive parameters in inbred and nonin-bred women of the same community.

METHODS

Adult members of the Mennonitecommunity of Goessel were invited toparticipate in a multidisciplinary studyon aging in January, 1980. The researchteam which included anthropologists,sociologists, psychologists, physiolo-gists, and medical doctors established aresearch clinic to provide a meetingplace where the data could be collected.Five hundred and seventy (570) individ-uals participated in the Goessel researchclinic. This number represents 51 percent of the adult resident membership ofAlexanderwohl, Tabor, and Goesselchurches. The participants consisted of258 males and 312 females.

Women attending the clinic wereasked to fill out a reproductive historyquestionnaire. The questionnaire ob-

tained information on age of menarcheand menopause, number of living chil-dren, pregnancies and fetal wastage(miscarriages and stillborns), and if theindividual had undergone hormonetreatment, used the pill, or undergonesurgery affecting reproductive organs.

Pedigree data were collected at theMennonite Historical Library in NorthNewton, Kansas, and at the Alexan-derwohl Church in Goessel by LaurineRogers, formerly of the Department ofAnthropology, University of Kansas.Of the pedigrees collected, 62.5 per centwere five generations or more and 37.5per cent were four generations or less.Inbreeding coefficients were calculatedaccording to the method of Wright(1922) by Dr. Rogers.

Reproductive variables of the inbredand noninbred women were comparedusing Student's t test. For analyses ofmenopause and length of reproductivespan, all women who had surgery(oophorectomy or hysterectomy) orwho had used the pill or had undergonehormone treatment were excluded fromthe analysis. Women using other formsof birth control were not excluded.Comparisons of numbers of childrenand fetal wastage (miscarriages and still-borns) used data from women who hadcompleted their families. Women whohad experienced natural or surgicalmenopause formed this group.

Further analyses included regressingthe reproductive parameters on F (in-breeding coefficient) and a Pearson'scorrelation matrix of the parameters.Because there was such a wide range inthe degrees of inbreeding among thewomen, the inbred group was dividedinto three levels of inbreeding. The lev-els were determined by the F value thatis equivalent to the "n" values of the in-breeding coefficient formula, F = 4 x

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182 Moore Social Biology

V2" (Wright, 1922). The reproductivevariables in each inbreeding level wereanalyzed by Student's t test to determineif degree of inbreeding had effects onthe parameters.

Both age at menarche and age ofmenopause constitute recall data. Theinaccuracy of retrospective data is welldocumented (Damon et al., 1969).However, in order to examine the ef-fects of parental inbreeding, one mustknow age of menarche and menopausein the same woman. Except for a fewstudies like Treloar's (1974) large pro-spective study in Minnesota, longitudi-nal data are not used. Therefore, moststatus quo studies collect menarchealdata from school girls and menopausaldata from an older female group. In thisstudy, one has to use recall data so thatage at menarche and age of menopauseare obtained from the same woman.

RESULTS

Of the 312 female participants in theresearch clinic, 279 completed repro-ductive histories. The women ranged inage from 18 to 93 with an average age of54.5 years. Of the 279 women, pedi-grees had been previously constructedfor 194 of the women answering thequestionnaires. Sixty-four (64) of thesewomen were inbred and 130 were not in-bred. Individual inbreeding coefficients(F) ranged from a low of 0.00024 to ahigh of 0.0332. The average F of thegroup of women for which pedigreeswere available was 0.003.

Table 1 compares five reproductiveparameters between inbred and nonin-bred females. Women in the inbredgroup have F > 0 and women in thenoninbred group have F = 0. The num-bers (n) in each category of the analysisdiffer because some women did not an-

TABLE1

COMPARISON OF REPRODUCTIVE PARAMETERSIN INBRED AND NONINBRED WOMEN

Parameters n" Mean SD (Values*

MenarcheInbred 63 12.9 1.54 1.41Noninbred . . 122 12.6 1.47

MenopauseInbred 28 49.5 3.18 0.22Noninbred . . 40 49.3 3.98

SpanInbred 27 36.3 3.22 0.70Noninbred . . 37 36.9 3.84

ChildrenInbred 52 2.9 1.73 0.33Noninbred . . 94 3.0 1.84

Fetal wastageInbred 52 0.31 0.781 1.10Noninbred . . 94 0.46 0.757

"Numbers vary because some women did not answerevery question, and some women could not answer each ques-tion because of their reproductive status.

'For each 1 value, p > 0.05.

swer every question and others couldnot answer each question because oftheir reproductive status (had notreached menopause, had not completedtheir family, had surgical menopause orhormonal treatment, etc.). For exam-ple, some individuals did not give age ofmenarche; others had not reached men-opause. Both of these factors would af-fect the w's of each of the five parametercategories.

Although the inbred group does havea later menarche and a shorter repro-duction span, these differences are notstatistically significant, as in age of men-opause. Live children and fetal deathswere compared in inbred and noninbredwomen who had completed their fami-lies. Fetal wastage is the average num-ber of spontaneous abortions or still-births per woman. The two groups hadessentially the same average number ofchildren. The inbred group experienced

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Vol. 34, No. Mennonites in Kansas 183

less, instead of more, fetal loss. How-ever, this difference was not significantaccording to the t test.

To examine further the effects of in-breeding on reproductive factors, weperformed regressions of age at menar-che, age at menopause, reproductivespan, number of children, and fetalwastage on F coefficients > 0. Neithermenarche, menopause, reproductivespan, nor fetal loss was significantly af-fected by the degree of inbreeding.However a significant regression coef-ficient of 0.37 (p < 0.02) was obtainedwhen number of children was regressedwith F. In other words, women with ahigher degree of inbreeding had morechildren. This of course is the oppositeof the prediction of the working hypoth-esis that inbreeding will depress repro-ductive fitness.

Pearson's correlation coefficients,shown in Table 2, essentially confirm theresults of the regression analyses. Thereis no significant correlation between Fcoefficient and menarche, menopause,and fetal wastage; and there is a positivecorrelation with number of children.Reproductive span is also significantlycorrelated with F. Again, this is not ex-pected with the working hypothesis thatinbred women have shorter reproduc-tive spans.

TABLE2

CORRELATION COEFFICIENTS OF INBREEDINGCOEFFICIENT (F) WITH REPRODUCTIVE

PARAMETERS

Parameters n r p

Menarche 63 0.0035 p>0.05Menopause 28 0.2671 p>0.05Span 27 0.3385 p<0.05Children 52 0.3702 p<0.0\Fetal wastage . . . . 52 0.1612 p>0.05

In an attempt to elucidate why inbredwomen have more children, the datawere examined to see if age were correl-ated with F by regressing number ofchildren with age. This could demon-strate a possible volitional shift to asmaller family size in younger womenand a possible lower degree of inbreed-ing in younger women. Neither statisticwas significant; neither family size nor Fhas a relationship to age in this sample.

Since there is such a large differencein degrees of inbreeding among thewomen (0.00024—0.0332), the F coef-ficients were divided into three groups:Group 1 is the least inbred withF< 0.0039; Group 2 is the intermediatelevel with F values = 0.0040—0.0156;and Group 3 is the most highly inbredwith F> 0.0156. Student's t tests wereused to compare each inbred group bypairs in order to see if the level of in-breeding was affecting age of menarche,age of menopause, length of reproduc-tive span, number of children and fetalloss. Figure 1 shows the comparison ofthe three levels of inbreeding and repro-ductive parameters. The n's vary in eachparameter category for the same rea-sons given earlier. There is one less indi-vidual in the high Fgroup and reproduc-tive span because one woman did notreport age of menarche. The women inthe three inbred groups whose data areanalyzed in the children and fetal wast-age categories are women who had ex-perienced natural or surgical meno-pause. No significant differences wereseen comparing menarche, menopause,span, number of children, and fetalwastage. Though not statistically signi-ficant, the high inbred group surpris-ingly had an earlier menarche, latermenopause, longer reproductive span,and more children per woman than thelow inbred group. These results are the

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184 Moore Social Biology

D low level (F<0.0039)

H medium level (F=0.0040-0.0156)

• high level(F>0.0156)

Menopause

14.0

13.5

§13.0

12.5

12.0

Menarche

n=28n=22

iI

n=13

//

60.0

50.5

50.0

49.5

49.0

48.5

48.0

r

n=10

n=10

•n

iiIii

7/////

38.0

37.5

37.0

36.5

S 3 6 -°35.5

35.0

34.5

34.0

ReproductiveSpan

n=10

mM

n=10

n=7

//////////////

o 3.5

* 3.0CD

I" 2.5CD

2.0

Children

n=14

n=26

n=127"//////

0.70

1 § 0.60ja E= § 0.50

£ c 0.40

ols 0.30

§ 2 0.20> o0.10

Fetal Wastage

n=12

v

• n=26

n=14

FIG. 1.—Comparison of the three levels of inbreeding and reproductive parameters.

opposite expected by the inbreeding de-pression hypothesis. Only with a higherfetal wastage did the high inbred groupmeet the expectation of the hypothesis.However, as stated above, none of thesedifferences is statistically significant.

DISCUSSION

If inbreeding has the same deleteri-ous effects on reproductive perform-ance in humans as it does in many ani-mal species, it would be reasonable to

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Vol. 34, No. Mennonites in Kansas 185

expect the inbred women would havelater menarches, earlier menopauses,shorter reproductive spans, fewer chil-dren, and more fetal wastage. Theresults of this study do not support thishypothesis. Except for two positive cor-relations of children and reproductivespans with inbreeding coefficient, thereappears to be no difference between in-bred and noninbred women. Comparedto animal studies, this analysis is limitedby the small sample size and by the low Fcoefficients in general. Inbreeding de-pression among animals is often studiedin full sib matings where the Fof the off-spring is 0.25.

A review of the literature has notfound any other studies that analyzedthe effect of degree of inbreeding on ageof menarche, age of menopause, andlength of reproductive span. Howeverthere have been many studies investigat-ing inbreeding and human fertility.None of the largest and best designedstudies has demonstrated a consistentsignificant effect of parental consan-guinity on the frequency of deaths(Schull, 1958, 1959; Schull and Neel,1965; Schull et al., 1970a; Schull et al.,19706; Schull and Neel, 1972; Hook andSchull, 1973; Rao and Inbaraj, 1977).These references are studies of Schull,Neel, and their colleagues in Hiroshimaand Nagasaki and later in Hirado, Ja-pan, and the investigations of Rao andInbaraj in Tamil Nadu, South India. Inrelation to the positive correlation be-tween F and number of children foundin this paper, it is noteworthy that theparental inbreeding portion of theHirado study showed that inbred wiveshad significantly more pregnancies andlivebirths than noninbred wives (Schullet al., 1970a). In Schull's study, the in-breeding coefficients of the inbred sam-

ple ranged from second cousins to firstcousins (F = 0.0156 to 0.06). The Men-nonite women were not as highly in-bred; only 15 of the sample had F valuesin the range of 0.015 to 0.06 and of thosenone had a F value higher than 0.0332.

Aside from Schull's and his col-leagues' study in Hirado, there are onlytwo other reports dealing with parentalinbreeding. Warburton and Fraser(1964) in their analysis of reproductivehistories of women at Montreal Chil-dren's Hospital found no difference be-tween abortion frequency among wivesof inbred and noninbred husbands. Inanother study, Tanaka et al. (1967)found a significant increase in sterilityamong inbred wives, but no effect in in-bred husbands living in Hoshino andKurogi, Japan.

CONCLUSION

In conclusion, there is no consistentevidence that inbreeding significantlyaffects the reproductive parameters ofage of menarche, age of menopause,length of reproductive span, number ofchildren, and fetal loss in this sample ofMennonite women. The next step in theanalysis of this sample is to establishwhich of the husbands of these womenare inbred and to obtain their F coef-ficients. In view of previous studies,however, the conclusions outlined inthis paper will probably stay the same: ifinbreeding does have an effect on thesereproductive parameters, it is too smallto be detected in this sample.

ACKNOWLEDGMENTS

The author would like to thank MichaelH. Crawford, who organized the multidis-ciplinary study on aging, and Laurine Rog-

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186 Moore Social Biology

ers, who computed the inbreeding coef-ficients. This work was supported in part by aNational Institute of Aging Grant

AGO6146-02 of which M. H. Crawford wasa principal investigator.

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lation genetic models in the study of agingand longevity in a Mennonite community.Soc. Sci. Med. 16:149-153.

DAMON, A., S. T. DAMON, R. B. REED, and J.VALADIAN. 1969. Age at menarche of moth-ers, with a note on accuracy of recall. Hum.Biol. 41:161-175.

FALCONER, D. S. 1960. Quantitative genetics.Ronald Press, New York.

HOOK, E. B., and W. J. SCHULL. 1973. Why isthe XX fitter? Evidence consistent with aneffect of X-heterosis in the human femalefrom sex ratio data in offspring of firstcousin marriages. Nature 244:570-573.

RAO, P. S. S., and S. G. INBARAJ. 1977. In-breeding effects on human reproduction inTamil Nadu of South India. Ann. Hum.Genet. Lond. 41:87-98.

SCHULL, W. J. 1958. Empirical risks in consan-guineous marriages: Sex ratio, malforma-tion and viability. Amer. J. Hum. Genet.10:294-343.

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SCHULL, W. J., T. FURUSHO, M. YAMAMOTO, H.NAGANO, and I. KOMATSU. 1970. The effectof parental consanguinity and inbreeding inHirado, Japan. Humangenetik 9:294-315.

SCHULL, W. J., H. NAGANO, M. YAMAMOTO,and I. KOMATSU. 1970. The effects of paren-tal consanguinity and inbreeding in Hirado,Japan. I. Stillbirths and prereproductivemortality. Amer. J. Hum. Genet. 22:239-386.

SCHULL, W. J., and J. V. NEEL. 1965. The ef-fects of inbreeding on Japanese children.Harper and Row, New York.

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TANAKA, K., N. OHTSUKI, and T. FURUSHO.1967. Effects of maternal inbreeding on pre-natal deaths in man. Proc. Japan Acad.43:801-806.

TRELOAR, A. E. 1974. Menarche, menopauseand intervening fecundability. Hum. Biol.46:89-107.

WARBURTON, D., and F. C. FRASER. 1964.Spontaneous abortion risks in man: Datafrom reproductive histories collected in amedical genetics unit. Amer. J. Hum.Genet. 16:1-25.

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