Marriage patterns drive fertility decline

Jul 21, 2010
This is one of the images from pre-industrial Finnish church records used in the study. Credit: Virpi Lummaa

Researchers at the University of Sheffield have applied an evolutionary 'use it or lose it' principle when studying past marriage patterns, to show that marriage can influence the evolution of age-patterns of fertility.

Researchers Duncan Gillespie, Dr Virpi Lummaa and Dr Andrew Russell, from the University's Department of Animal and Plant Sciences, studied Finnish church records from the 18th and 19th centuries, a time during which almost everyone married and divorce was forbidden, to trace the survival and histories of 1,591 women.

They found that women aged 30-35 were the most likely to be married. Those that married wealthy husbands were married at a younger age but to relatively older men, thereby gaining the family size-benefits of wealth but also an increased risk of widowhood. This high chance of widowhood, coupled with low re-marriage prospects for older widows with children, limited the percentage of women in the population with the opportunity to reproduce at older ages.

In today's society however, women do not start childbearing until an older age as marriage is often delayed, and casual or short-term relationships and divorce are more common. As a result, the natural selection maintaining young-age fertility might weaken and the relative strength of on old-age fertility could increase, something that could potentially lead to improvements in old-age fertility over many generations.

This is one of the images from pre-industrial Finnish church records used in the study. Credit: Virpi Lummaa

Duncan Gillespie from the University of Sheffield's Department of Animal and Plant Sciences, said: "In today's society, family-building appears to be increasingly postponed to older ages, when relatively few women in our evolutionary past would have had the opportunity to reproduce. As a result, this could lead to future evolutionary improvements in old-age female fertility.

"Childbearing within a relationship is still the norm in modern society, but at ages where fewer have the chance to reproduce, we should expect the evolution of lower fertility."

Explore further: A two generation lens: Current state policies fail to support families with young children

More information: Read the full paper entitled Pair-bonding modifies the age-specific intensities of natural selection on human female fecundity at the following link: www.ncbi.nlm.nih.gov/pubmed/20536363

Provided by University of Sheffield

4 /5 (6 votes)
add to favorites email to friend print save as pdf

Related Stories

Mothers trade child quantity for quality

Jan 23, 2008

Researchers at the University of Sheffield have shown that mothers are choosing to have fewer children in order to give their children the best start in life, but by doing so are going against millenia of human evolution. ...

Divorce reduces chance of new, successful relationship

Sep 07, 2007

After a separation or divorce the chances of marrying or cohabiting again decrease. In particular, a previous marriage or children from a previous relationship, reduce the chances of a new relationship. Moreover, the prospects ...

Recommended for you

Scholar tracks the changing world of gay sexuality

Sep 19, 2014

With same-sex marriage now legalized in 19 states and laws making it impossible to ban homosexuals from serving in the military, gay, lesbian and bisexual people are now enjoying more freedoms and rights than ever before.

User comments : 0