scholarly journals Mega-analysis of 31,396 individuals from 6 countries uncovers strong gene-environment interaction for human fertility

2016 ◽  
Author(s):  
Felix C. Tropf ◽  
Renske M. Verweij ◽  
Peter J. van der Most ◽  
Gert Stulp ◽  
Andrew Bakshi ◽  
...  
Keyword(s):  
Individual Differences ◽  
Twin Studies ◽  
Genetic Effects ◽  
Age At First Birth ◽  
Environment Interaction ◽  
First Birth ◽  
Time And Space ◽  
Number Of Children ◽  
Human Fertility ◽  
Gene Environment

AbstractFamily and twin studies suggest that up to 50% of individual differences in human fertility within a population might be heritable. However, it remains unclear whether the genes associated with fertility outcomes such as number of children ever born (NEB) or age at first birth (AFB) are the same across geographical and historical environments. By not taking this into account, previous genetic studies implicitly assumed that the genetic effects are constant across time and space. We conduct a mega-analysis applying whole genome methods on 31,396 unrelated men and women from six Western countries. Across all individuals and environments, common single-nucleotide polymorphisms (SNPs) explained only ~4% of the variance in NEB and AFB. We then extend these models to test whether genetic effects are shared across different environments or unique to them. For individuals belonging to the same population and demographic cohort (born before or after the 20th century fertility decline), SNP-based heritability was almost five times higher at 22% for NEB and 19% for AFB. We also found no evidence suggesting that genetic effects on fertility are shared across time and space. Our findings imply that the environment strongly modifies genetic effects on the tempo and quantum of fertility, that currently ongoing natural selection is heterogeneous across environments, and that gene-environment interactions may partly account for missing heritability in fertility. Future research needs to combine efforts from genetic research and from the social sciences to better understand human fertility.Authors SummaryFertility behavior – such as age at first birth and number of children – varies strongly across historical time and geographical space. Yet, family and twin studies, which suggest that up to 50% of individual differences in fertility are heritable, implicitly assume that the genes important for fertility are the same across both time and space. Using molecular genetic data (SNPs) from over 30,000 unrelated individuals from six different countries, we show that different genes influence fertility in different time periods and different countries, and that the genetic effects consistently related to fertility are presumably small. The fact that genetic effects on fertility appear not to be universal could have tremendous implications for research in the area of reproductive medicine, social science and evolutionary biology alike.

scholarly journals Social Science Genetics and Fertility

2018 ◽  
Author(s):  
Felix C Tropf
Keyword(s):  
Molecular Genetic ◽  
Age At First Birth ◽  
Life Outcomes ◽  
Environment Change ◽  
Fertility Choice ◽  
Number Of Children ◽  
Human Fertility ◽  
First Child ◽  
Molecular Genetic Data ◽  
The Social

To what extent do genes influence the age at which you have your first child and the total number of children that you have? Does the (social) environment change genetic effects on fertility? Do genes lead to spurious associations between life outcomes such as education and age at first birth? The social sciences have been reticent to integrate a genetic approach to the study of fertility choice and behaviour, resulting in theories and findings that are largely socially deterministic. This dissertation investigates genetic and environmental influences on human fertility—aswell as their interplay—using both twin data as well as molecular genetic data of more than 31,000 genotyped individuals from 6 countries.

Examining the link between religiousness and fitness in a behavioural ecological framework

2019 ◽  
Vol 52 (5) ◽  
pp. 756-767 ◽  
Author(s):  
Janko Međedović
Keyword(s):  
Life History ◽  
Reproductive Success ◽  
Parental Investment ◽  
Life History Theory ◽  
Community Sample ◽  
Future Research ◽  
Harsh Environment ◽  
Age At First Birth ◽  
First Birth ◽  
Number Of Children

AbstractIn recent years there have been attempts to explain religiousness from an evolutionary viewpoint. However, empirical data on this topic are still lacking. In the present study, the behavioural ecological theoretical framework was used to explore the relations between religiousness, harsh environment, fitness (reproductive success and parental investment) and fitness-related outcomes (age at first birth, desired number of children and the romantic relationship duration). The data were collected from 461 individuals from a community sample who were near the end of their reproductive phase (54% females, Mage = 51.75; SD = 6.56). Positive links between religiousness, harsh environment, fitness and fitness-related outcomes were expected, with the exception of age at first birth, for which a negative association was hypothesized. Hence, the main assumption of the study was that religiousness has some attributes of fast life-history phenotypes – that it emerges from a harsh environment and enables earlier reproduction. The study findings partially confirmed these hypotheses. Religiousness was positively related to environmental harshness but only on a zero-order level. Religious individuals had higher reproductive success (this association was especially pronounced in males) but religiousness did not show associations with parental investment. Religiousness was positively associated with desired number of children and negatively associated with age at first birth, although the latter association was only marginally significant in the multivariate analyses. Finally, path analysis showed that desired number of children and age at first birth completely mediated the relation between religiousness and reproductive success. The data confirmed the biologically adaptive function of religiousness in contemporary populations and found the mediating processes that facilitate fitness in religious individuals. Furthermore, the findings initiate a more complex view of religiousness in a life-history context which could be fruitful for future research: a proposal labelled as ‘ontogeny-dependent life-history theory of religiousness’.

scholarly journals Intelligence and Fitness: The Mediating Role of Educational Level

2017 ◽  
Vol 15 (2) ◽  
pp. 147470491770693 ◽  
Author(s):  
Janko Međedović
Keyword(s):  
Reproductive Success ◽  
Cognitive Abilities ◽  
Evolutionary Status ◽  
Age At First Birth ◽  
First Birth ◽  
Short Term ◽  
Number Of Children ◽  
Mediating Role ◽  
Fitness Indicators

The evolutionary status of intelligence is not clear: It is positively related to various indicators of fitness but negatively to reproductive success as the most important fitness marker. In the present research, we explored the links between intelligence and three fitness indicators: number of children (short-term reproductive success), number of grandchildren (long-term reproductive success), and age at first birth. Participants were individuals in a postreproductive stage ( N = 191; mean age = 66.5 years). Intelligence had a positive correlation with short-term reproductive success and age at first birth but a negative correlation with long-term reproductive success. Participants’ education turned out to be a significant mediator of the link between intelligence and criterion measures. The results showed that intelligence can elevate short-term reproductive success. Furthermore, individuals with higher intellectual abilities tended to delay reproduction, which negatively affected their long-term reproductive success. Education was revealed as a very important resource which affects the link between cognitive abilities and fitness, thus proving its evolutionary role in contemporary populations.

scholarly journals Maternal age at first birth and offspring criminality: Using the children of twins design to test causal hypotheses

2013 ◽  
Vol 25 (1) ◽  
pp. 17-35 ◽  
Author(s):  
Claire A. Coyne ◽  
Niklas Långström ◽  
Martin E. Rickert ◽  
Paul Lichtenstein ◽  
Brian M. D'Onofrio
Keyword(s):  
Antisocial Behavior ◽  
Maternal Age ◽  
Monozygotic Twin ◽  
Age At First Birth ◽  
Causal Association ◽  
First Birth ◽  
Criminal Convictions ◽  
Children Of Twins ◽  
Gene Environment ◽  
Selection Factors

AbstractTeenage childbirth is a risk factor for poor offspring outcomes, particularly offspring antisocial behavior. It is not clear, however, if maternal age at first birth (MAFB) is causally associated with offspring antisocial behavior or if this association is due to selection factors that influence both the likelihood that a young woman gives birth early and that her offspring engage in antisocial behavior. The current study addresses the limitations of previous research by using longitudinal data from Swedish national registries and children of siblings and children of twins comparisons to identify the extent to which the association between MAFB and offspring criminal convictions is consistent with a causal influence and confounded by genetic or environmental factors that make cousins similar. We found offspring born to mothers who began childbearing earlier were more likely to be convicted of a crime than offspring born to mothers who delayed childbearing. The results from comparisons of differentially exposed cousins, especially born to discordant monozygotic twin sisters, provide support for a causal association between MAFB and offspring criminal convictions. The analyses also found little evidence for genetic confounding due to passive gene–environment correlation. Future studies are needed to replicate these findings and to identify environmental risk factors that mediate this causal association.

A Nuclear Twin Family Study of Self–Esteem

2018 ◽  
Vol 32 (3) ◽  
pp. 221-232 ◽  
Author(s):  
Wiebke Bleidorn ◽  
Anke Hufer ◽  
Christian Kandler ◽  
Christopher J. Hopwood ◽  
Rainer Riemann
Keyword(s):  
Individual Differences ◽  
Environmental Influences ◽  
Twin Studies ◽  
Self Esteem ◽  
Personality Psychology ◽  
Gene Environment ◽  
Environmental Component ◽  
Increased Sensitivity ◽  
Nationally Representative ◽  
Twin Families

Twin studies suggest that both genes and environments influence the emergence and development of individual differences in self–esteem. However, different lines of research have emphasized either the role of genes or of environmental influences in shaping self–esteem, and the pathways through which genes and environments exert their influence on self–esteem remain largely unclear. In this study, we used nationally representative data from over 2000 German twin families and a nuclear twin family design (NTFD) to further our understanding of the genetic and environmental influences on individual differences in self–esteem. Compared with classical twin designs, NTFDs allow for finer–grained descriptions of the genetic and environmental influences on phenotypic variation, produce less biased estimates of those effects, and provide more information about different environmental influences and gene–environment correlation that contribute to siblings’ similarity. Our NTFD results suggested that additive and non–additive genetic influences contributed to individual differences in self–esteem as well as environmental influences that are both shared and not shared by twins. The shared environmental component mostly reflected non–parental influences. These findings highlight the increased sensitivity afforded by NTFDs but also remaining limitations that need to be addressed by future behavioural genetic work on the sources of self–esteem. Copyright © 2018 European Association of Personality Psychology

scholarly journals Fertility Postponement and Regional Patterns of Dispersion in Age at First Birth: Descriptive Findings and Interpretations

2019 ◽  
Vol 44 ◽  
Author(s):  
Mathías Nathan ◽  
Ignacio Pardo
Keyword(s):  
North America ◽  
Family Formation ◽  
Developed Countries ◽  
The United States ◽  
Age At First Birth ◽  
First Birth ◽  
Regional Patterns ◽  
Human Fertility ◽  
Using Data ◽  
The Postponement

Previous studies have documented an increasing heterogeneity in first-birth timing in countries experiencing the postponement transition. Sobotka (2004), for instance, showed a rising dispersion in age at first birth in developed countries, particularly in the United Kingdom and the United States, where the timing polarisation between more and less advantaged women is most evident. However, these studies have included few countries outside Europe and North America, and lack a thorough interpretation of the rising dispersion in first births. Our aim is to compare the evolution of dispersion in age at first birth in countries in Europe, East Asia, North America and South America. Using data from the Human Fertility Database and the Human Fertility Collection, we describe the evolution of the period mean age at first birth and its variance for 21 countries since 1970. In line with previous studies, our results show a widespread pattern of increasing heterogeneity in age at first birth after the onset of the postponement transition, although with marked differences among regions and countries. The greatest heterogeneity can be found in countries where timing of family formation varies greatly among women with different socioeconomic status. Chile and Uruguay, in particular, exhibit the highest heterogeneity even though they are at the beginning of the postponement transition. There is no general explanation of why dispersion increased as the mean age at first birth rose. Further studies in this area should investigate causes and interpretations of this trend, and develop measures for studying heterogeneity in fertility timing.

Genetics

2018 ◽  
Author(s):  
Carol Kan ◽  
Ma-Li Wong
Keyword(s):  
Complex Traits ◽  
Association Studies ◽  
Genetic Correlations ◽  
Twin Studies ◽  
Epidemiological Studies ◽  
Environment Interaction ◽  
Genome Wide Association Studies ◽  
Small Magnitude ◽  
Gene Environment ◽  
Genetic Overlap

An association between type 2 diabetes mellitus (T2DM) and depression has been reported in epidemiological studies. Finding a genetic overlap between T2DM and depression will provide evidence to support a common biological pathway to both disorders. Genetic correlations observed from twin studies indicate that a small magnitude of the variance in liability can be attributed to genetic factors. However, no genetic overlap has been observed between T2DM and depression in genome-wide association studies using both the polygenic score and the linkage disequilibrium score regression approaches. Clarifying the shared heritability between these two complex traits is an important next step towards better therapy and treatment. Another area that needs to be explored is gene–environment interaction, since genotypes can affect an individual’s responses to the environment and environment can differentially affect genotypes expression.

scholarly journals Schizophrenia risk and reproductive success: a Mendelian randomization study

2019 ◽  
Vol 6 (3) ◽  
pp. 181049 ◽  
Author(s):  
Rebecca B. Lawn ◽  
Hannah M. Sallis ◽  
Amy E. Taylor ◽  
Robyn E. Wootton ◽  
George Davey Smith ◽  
...  
Keyword(s):  
Reproductive Success ◽  
Mendelian Randomization ◽  
Causal Effect ◽  
Sexual Partners ◽  
Age At First Birth ◽  
First Birth ◽  
Genetic Liability ◽  
Number Of Children ◽  
Fitness Advantage ◽  
Number Of Sexual Partners

Schizophrenia is a debilitating and heritable mental disorder associated with lower reproductive success. However, the prevalence of schizophrenia is stable over populations and time, resulting in an evolutionary puzzle: how is schizophrenia maintained in the population, given its apparent fitness costs? One possibility is that increased genetic liability for schizophrenia, in the absence of the disorder itself, may confer some reproductive advantage. We assessed the correlation and causal effect of genetic liability for schizophrenia with number of children, age at first birth and number of sexual partners using data from the Psychiatric Genomics Consortium and UK Biobank. Linkage disequilibrium score regression showed little evidence of genetic correlation between genetic liability for schizophrenia and number of children ( r g = 0.002, p = 0.84), age at first birth ( r g = −0.007, p = 0.45) or number of sexual partners ( r g = 0.007, p = 0.42). Mendelian randomization indicated no robust evidence of a causal effect of genetic liability for schizophrenia on number of children (mean difference: 0.003 increase in number of children per doubling in the natural log odds ratio of schizophrenia risk, 95% confidence interval (CI): −0.003 to 0.009, p = 0.39) or age at first birth (−0.004 years lower age at first birth, 95% CI: −0.043 to 0.034, p = 0.82). We find some evidence of a positive effect of genetic liability for schizophrenia on number of sexual partners (0.165 increase in the number of sexual partners, 95% CI: 0.117–0.212, p = 5.30×10 −10 ). These results suggest that increased genetic liability for schizophrenia does not confer a fitness advantage but does increase mating success.

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