What is the influence of genetics on age at first birth and number of children?

Last week I had the opportunity to speak with Kayla Schulte from Oxford University about the Sociogenome research project, a "comprehensive study of the role of genes and gene-environment (GxE) interaction on reproductive behaviour. Until now, social science research has focussed on socio-environmental explanations, largely neglecting the role of genes.

Drawing from recent unprecedented advances in molecular genetics we examine whether there is a genetic component to reproductive outcomes, including age at first birth, number of children and infertility and their interaction with the social environment."

Although there is evidence of genetics influencing traits, including facial features, I'd always assumed socio-environmental factors played a dominant role in demographics and that if genetics played a role it would be through correlations, such as genetics associated with the Irish would also be associated with larger numbers of children.

The Sociogenome project is building on an article published in final form as: Nature Genetics 2016 December ; 48(12): 1462–1472. doi:10.1038/ng.3698.

Genome-wide analysis identifies 12 loci influencing human reproductive behavior 
Abstract
The genetic architecture of human reproductive behavior – age at first birth (AFB) and number of children ever born (NEB) – has a strong relationship with fitness, human development, infertility and risk of neuropsychiatric disorders. However, very few genetic loci have been identified and the underlying mechanisms of AFB and NEB are poorly understood. We report the largest genome- wide association study to date of both sexes including 251,151 individuals for AFB and 343,072 for NEB. We identified 12 independent loci that are significantly associated with AFB and/or NEB in a SNP-based genome-wide association study, and four additional loci in a gene-based effort. These loci harbor genes that are likely to play a role – either directly or by affecting non-local gene expression – in human reproduction and infertility, thereby increasing our understanding of these complex traits.

Although the article is behind a paywall a table with a list of the loci identified is table 1 at https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5695684/.

If you're interested you can check to see if your DNA results suggest an influence on your age at birth of your first child and number of children ever born.