Dorret I Boomsma

DP Schmitt

K Dawood

KM Kirk

LF Cherkas

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Twin Research: Exploring female sexuality

Boomsma, D.I.

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Exploring female sexuality

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VU Research PortalExploring female sexualityBoomsma, D.I.published inEuropean Journal of Human Genetics2005DOI (link to publisher)10.1038/sj.ejhg.5201420document versionPublisher's PDF, also known as Version of recordLink to publication in VU Research Portalcitation for published version (APA)Boomsma, D. I. (2005). Exploring female sexuality. European Journal of Human Genetics, 13, 696-697.https://doi.org/10.1038/sj.ejhg.5201420General rightsCopyright and moral rights for the publications made accessible in the public portal are retained by the authors and/or other copyright ownersand it is a condition of accessing publications that users recognise and abide by the legal requirements associated with these rights.            • Users may download and print one copy of any publication from the public portal for the purpose of private study or research.            • You may not further distribute the material or use it for any profit-making activity or commercial gain            • You may freely distribute the URL identifying the publication in the public portal ?Take down policyIf you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediatelyand investigate your claim.E-mail address:vuresearchportal.ub@vu.nlDownload date: 03. Mar. 2023genes in a diagnostic setting: genotype–phenotype correlations and comparison ofdiagnostic DNA techniques in tuberoussclerosis complex. Eur J Human Genet2005; 13: 731–741.2 Jones AC, Shyamsundar MM, Thomas MWet al: Comprehensive mutation analysis ofTSC1 and TSC2-and phenotypic correla-tions in 150 families with tuberous sclero-sis. Am J Hum Genet 1999; 64: 1305–1315.3 Dabora SL, Jozwiak S, Franz DN et al:Mutational analysis in a cohort of 224tuberous sclerosis patients indicates in-creased severity of TSC2, compared withTSC1, disease in multiple organs. Am J HumGenet 2001; 68: 64–80.4 Sampson JR, Maheshwar MM, Aspinwall Ret al: Renal cystic disease in tuberoussclerosis: role of the polycystic kidneydisease 1 gene. Am J Hum Genet 1997; 61:843–851.5 Roberts PS, Dabora S, Thiele EA, Franz DN,Jozwiak S, Kwiatkowski DJ: Somatic mosai-cism is rare in unaffected parents ofpatients with sporadic tuberous sclerosis.J Med Genet 2004; 41: e69.6 Mayer K, Ballhausen W, Leistner W, Rott H:Three novel types of splicing aberrations inthe tuberous sclerosis TSC2 gene caused bymutations apart from splice consensussequences. Biochim Biophys Acta 2000;1502: 495–507.7 Li Y, Corradetti MN, Inoki K, Guan KL:TSC2: filling the GAP in the mTOR signal-ing pathway. Trends Biochem Sci 2004; 29:32–38.Twin Research. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .Exploring female sexualityDorret I Boomsma. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .European Journal of Human Genetics (2005) 13, 696–697.doi:10.1038/sj.ejhg.5201420Published online 6 April 2005Two recent twin studies providesome fascinating insights into justhow much of a role genes play indetermining variation in female sexualbehavior and debunk the common as-sumption that such behaviors are notheritable.Twin researchers have always shown akeen interest in exploring the causes ofvariation in a broad range of human traitsand disorders. Two papers in the December2004 and February 2005 issues of TwinResearch & Human Genetics that mightattract some attention from a wider audi-ence focus on the heritability of infidelityin a large sample of female twins from theUK, and on orgasm in Australian women.Both papers go some way beyond thesimple estimation of heritability. Specifi-cally they include multivariate measuresof the behavior under study and try tocome up with evolutionary explanationsfor their findings. Moreover the UK paperreports on a genome-wide linkage scan,and examines the association of infidelitywith a candidate gene suggested by ani-mal studies.In the UK study, Cherkas et al1 surveyedover 1600 pairs of female twins aboutepisodes of infidelity, lifetime number ofsexual partners and their attitudes to-wards infidelity. The average age of thewomen was 50 years and a quarter of thesewere divorced. Around 40% of the varia-tion in the number of sexual partners andinfidelity was due to genetic factors. Thegenetic correlation between the two traitswas estimated at 0.47. Interestingly, genesinfluenced the variation in actual beha-vior, but genetic factors did not appear toinfluence women’s attitudes to infidelity.Women who had been faithful had aboutfour sexual partners, compared to eight inthe infidelity group. This number is quitelarge compared to a previous study’sestimate of the number of lifetime part-ners that women desire.2 For a timeinterval of the next 30 years, womenworldwide averaged a desire for 2.5 part-ners (by contrast men expressed a desirefor an average of 13 partners).Based on research in pair-bonding ani-mals, the authors tested for associationwith a single tandem repeat marker in oneof the exons of the argentine vasopressin1A receptor gene in 149 dizygotic pairs.No significant results were found. How-ever, given that there are 18 alleles at thismarker the power of these tests might belimited so the lack of significant associa-tions might not be so surprising. Thelinkage scan (in 515 dizygotic twin pairs)showed a maximum LOD score of 2.46 tochromosome 7 for number of sexualpartners and a LOD of 1.93 at chromo-some 20 for infidel behavior.Dawood et al3 surveyed an even largersample of twins from the Australian twinregister. In a truly anonymous study(twins from the same pair had to agreetogether on a 10-digit number that servedas an identifier) 3080 women respondedto three questions about the frequencywith which they reached orgasm duringsexual intercourse, during other activitieswith their partner and during masturba-tion. Significant twin correlations werefound for all three variables with correla-tions in monozygotic twins higher than indizygotic twins. Broad-sense heritabilitieswere between 29% (orgasm during inter-course) and 40% (masturbation). Correla-tions among the three phenotypes werenot very high, and neither were geneticcorrelations, which may be derived fromthe path diagrams that summarize themultivariate analyses.Both sets of authors discussed theirfindings in the context of sexual behavioras a fitness trait and addressed the com-mon assumption that such traits shouldshow zero heritabilities. Previous papersfrom the Australian twin register havealready demonstrated that this is notnecessarily true.4 However, it is surprisingthat neither paper tried to relate theirphenotype to fitness indicators such asnumber of offspring.Remarkably, after the demonstration ofsignificant heritability in females, neitherpaper in its discussion, speculates on thepossible expression of these genes in males.It is unlikely that the UK study hascollected data in males, as the UK twinregister consists almost entirely of femaletwins, but the Australian study might havecollected data in male twins, includingtwins from opposite-sex pairs. Nonethe-less, as the first studies to show significantNews and Commentaries696European Journal of Human Geneticsheritability for individual differences infemale sexual behavior these papers arelikely to be widely read and cited. Thereactions that these findings will provokein those that read them will doubtless bediverse. As suggested by the UK study, thediversity in attitudes shows no geneticbasis, whereas actual behavior does’Dorret I Boomsma is at the Department ofBiological Psychology, Vrije UniversiteitAmsterdam, The NetherlandsE-mail: DI.Boomsma@psy.vu.nlReferences1 Cherkas LF, Oelsner EC, Mak YT, Valdes A,Spector TD: Genetic influences on femaleinfidelity and number of sexual partners inhumans: a linkage and association study ofthe role of the vasopressin receptor gene(AVPR1A). Twin Res 2004; 7: 649–658.2 Schmitt DP, 188 members of the Interna-tional Sexuality Description Project: Uni-versal sex differences in the desire forsexual variety: tests from 52 nations, 6continents, and 13 islands. J PersonalitySocial Psychol 2003; 85: 85–104.3 Dawood K, Kirk KM, Bailey JM, AndrewsPW, Martin NG: Genetic and environmen-tal influences on the frequency of orgasmin women. Twin Res Hum Genet 2005; 8:27–33.4 Kirk KM, Blomberg SP, Duffy DL, HeathAC, Owens IPF, Martin NG: Natural selec-tion and quantitative genetics of life-history traits in Western women: a twinstudy. Evolution 2001; 55: 423–435.News and Commentaries697European Journal of Human Genetics

English

DSpace at VU

genes in a diagnostic setting: genotype–
phenotype correlations and comparison of
diagnostic DNA techniques in tuberous
sclerosis complex. Eur J Human Genet
2005; 13: 731–741.
2 Jones AC, Shyamsundar MM, Thomas MW
et al: Comprehensive mutation analysis of
TSC1 and TSC2-and phenotypic correla-
tions in 150 families with tuberous sclero-
sis. Am J Hum Genet 1999; 64: 1305–1315.
3 Dabora SL, Jozwiak S, Franz DN et al:
Mutational analysis in a cohort of 224
tuberous sclerosis patients indicates in-
creased severity of TSC2, compared with
TSC1, disease in multiple organs. Am J Hum
Genet 2001; 68: 64–80.
4 Sampson JR, Maheshwar MM, Aspinwall R
et al: Renal cystic disease in tuberous
sclerosis: role of the polycystic kidney
disease 1 gene. Am J Hum Genet 1997; 61:
843–851.
5 Roberts PS, Dabora S, Thiele EA, Franz DN,
Jozwiak S, Kwiatkowski DJ: Somatic mosai-
cism is rare in unaffected parents of
patients with sporadic tuberous sclerosis.
J Med Genet 2004; 41: e69.
6 Mayer K, Ballhausen W, Leistner W, Rott H:
Three novel types of splicing aberrations in
the tuberous sclerosis TSC2 gene caused by
mutations apart from splice consensus
sequences. Biochim Biophys Acta 2000;
1502: 495–507.
7 Li Y, Corradetti MN, Inoki K, Guan KL:
TSC2: filling the GAP in the mTOR signal-
ing pathway. Trends Biochem Sci 2004; 29:
32–38.
Twin Research
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Exploring female sexuality
Dorret I Boomsma
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
European Journal of Human Genetics (2005) 13, 696–697.
doi:10.1038/sj.ejhg.5201420
Published online 6 April 2005
T
wo recent twin studies provide
some fascinating insights into just
how much of a role genes play in
determining variation in female sexual
behavior and debunk the common as-
sumption that such behaviors are not
heritable.
Twin researchers have always shown a
keen interest in exploring the causes of
variation in a broad range of human traits
and disorders. Two papers in the December
2004 and February 2005 issues of Twin
Research & Human Genetics that might
attract some attention from a wider audi-
ence focus on the heritability of infidelity
in a large sample of female twins from the
UK, and on orgasm in Australian women.
Both papers go some way beyond the
simple estimation of heritability. Specifi-
cally they include multivariate measures
of the behavior under study and try to
come up with evolutionary explanations
for their findings. Moreover the UK paper
reports on a genome-wide linkage scan,
and examines the association of infidelity
with a candidate gene suggested by ani-
mal studies.
In the UK study, Cherkas et al1 surveyed
over 1600 pairs of female twins about
episodes of infidelity, lifetime number of
sexual partners and their attitudes to-
wards infidelity. The average age of the
women was 50 years and a quarter of these
were divorced. Around 40% of the varia-
tion in the number of sexual partners and
infidelity was due to genetic factors. The
genetic correlation between the two traits
was estimated at 0.47. Interestingly, genes
influenced the variation in actual beha-
vior, but genetic factors did not appear to
influence women’s attitudes to infidelity.
Women who had been faithful had about
four sexual partners, compared to eight in
the infidelity group. This number is quite
large compared to a previous study’s
estimate of the number of lifetime part-
ners that women desire.2 For a time
interval of the next 30 years, women
worldwide averaged a desire for 2.5 part-
ners (by contrast men expressed a desire
for an average of 13 partners).
Based on research in pair-bonding ani-
mals, the authors tested for association
with a single tandem repeat marker in one
of the exons of the argentine vasopressin
1A receptor gene in 149 dizygotic pairs.
No significant results were found. How-
ever, given that there are 18 alleles at this
marker the power of these tests might be
limited so the lack of significant associa-
tions might not be so surprising. The
linkage scan (in 515 dizygotic twin pairs)
showed a maximum LOD score of 2.46 to
chromosome 7 for number of sexual
partners and a LOD of 1.93 at chromo-
some 20 for infidel behavior.
Dawood et al3 surveyed an even larger
sample of twins from the Australian twin
register. In a truly anonymous study
(twins from the same pair had to agree
together on a 10-digit number that served
as an identifier) 3080 women responded
to three questions about the frequency
with which they reached orgasm during
sexual intercourse, during other activities
with their partner and during masturba-
tion. Significant twin correlations were
found for all three variables with correla-
tions in monozygotic twins higher than in
dizygotic twins. Broad-sense heritabilities
were between 29% (orgasm during inter-
course) and 40% (masturbation). Correla-
tions among the three phenotypes were
not very high, and neither were genetic
correlations, which may be derived from
the path diagrams that summarize the
multivariate analyses.
Both sets of authors discussed their
findings in the context of sexual behavior
as a fitness trait and addressed the com-
mon assumption that such traits should
show zero heritabilities. Previous papers
from the Australian twin register have
already demonstrated that this is not
necessarily true.4 However, it is surprising
that neither paper tried to relate their
phenotype to fitness indicators such as
number of offspring.
Remarkably, after the demonstration of
significant heritability in females, neither
paper in its discussion, speculates on the
possible expression of these genes in males.
It is unlikely that the UK study has
collected data in males, as the UK twin
register consists almost entirely of female
twins, but the Australian study might have
collected data in male twins, including
twins from opposite-sex pairs. Nonethe-
less, as the first studies to show significant
News and Commentaries
696
European Journal of Human Genetics
heritability for individual differences in
female sexual behavior these papers are
likely to be widely read and cited. The
reactions that these findings will provoke
in those that read them will doubtless be
diverse. As suggested by the UK study, the
diversity in attitudes shows no genetic
basis, whereas actual behavior does’
Dorret I Boomsma is at the Department of
Biological Psychology, Vrije Universiteit
Amsterdam, The Netherlands
E-mail: DI.Boomsma@psy.vu.nl
References
1 Cherkas LF, Oelsner EC, Mak YT, Valdes A,
Spector TD: Genetic influences on female
infidelity and number of sexual partners in
humans: a linkage and association study of
the role of the vasopressin receptor gene
(AVPR1A). Twin Res 2004; 7: 649–658.
2 Schmitt DP, 188 members of the Interna-
tional Sexuality Description Project: Uni-
versal sex differences in the desire for
sexual variety: tests from 52 nations, 6
continents, and 13 islands. J Personality
Social Psychol 2003; 85: 85–104.
3 Dawood K, Kirk KM, Bailey JM, Andrews
PW, Martin NG: Genetic and environmen-
tal influences on the frequency of orgasm
in women. Twin Res Hum Genet 2005; 8:
27–33.
4 Kirk KM, Blomberg SP, Duffy DL, Heath
AC, Owens IPF, Martin NG: Natural selec-
tion and quantitative genetics of life-
history traits in Western women: a twin
study. Evolution 2001; 55: 423–435.
News and Commentaries
697
European Journal of Human Genetics


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Exploring female sexuality

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