The Balancing Act of Life: How Having Children Historically Affected Lifespan in Rural Spain

– By Ángel Luis González Esteban & Francisco Marco-Gracia

For centuries, scientists have pondered a fundamental question: is there a biological trade-off between reproduction and longevity? In simpler terms, does having more children mean a shorter lifespan for mothers? This is a core idea in evolutionary theory, suggesting that bodies have limited resources, and investing heavily in having offspring might leave less for maintaining the mother’s health and extending her life.

While this idea has been supported by studies on animals, the picture in humans has been less clear, with many studies yielding conflicting results. This is often because it’s challenging to disentangle evolutionary factors from the complex mix of genetics, environment, and societal influences that shape human lives.

To shed more light on this, we delved into the rich historical records of rural Spain, specifically parish registers from 17 villages, spanning a remarkable five centuries, from 1536 to 1965. This allowed us to examine the lives of over 5,000 women, meticulously tracking their fertility and longevity, and even accounting for the experiences of their parents. This long-term perspective and the ability to consider intergenerational patterns are what make our study particularly valuable.

What Did the Data Reveal?

Our analysis revealed some fascinating insights into the historical relationship between motherhood and lifespan in this rural Spanish population:

– More Children, Shorter Lives: Overall, we found a significant negative impact of the number of children a woman had on her longevity. On average, each additional child was associated with a reduction in the mother’s lifespan. Having a large family (8 or more children, which was above average for any period in our study) was also clearly linked to reduced longevity. This suggests that the biological costs of pregnancy, childbirth, and potentially the demands of raising a large family did take a toll on women’s bodies over the long term.

– The Impact of Surviving Children: Interestingly, the number of children who survived past the age of five had an even stronger negative association with the mother’s lifespan. This highlights that the physical demands of childcare and breastfeeding likely played a significant role in the wear and tear on mothers, beyond just the act of pregnancy itself. Even considering that mothers with more children might have received more support, the negative effects on their longevity seemed to outweigh any potential benefits.

– The Timing of Motherhood Mattered: Having a first child at a very young age (before 25, and especially before 20) was associated with shorter lifespans. This could be because early motherhood, especially in a time of limited resources, placed a greater strain on still-developing bodies and was often linked to longer reproductive periods. Conversely, having the last child after the age of 40 was linked to increased longevity. This might seem counterintuitive, but it likely reflects that women who were healthy enough to conceive and carry a pregnancy to term at a later age were already predisposed to longer lives.

– The Pace of Reproduction: We also looked at birth intervals and the total length of a woman’s reproductive life. While the average time between births didn’t show a strong link to lifespan on its own, women with a long reproductive span (over 15 years) combined with consistently short birth intervals (what we termed “natural fertility”) lived significantly shorter lives, on average about 1.5 years less than others. This suggests that insufficient recovery time between pregnancies could accelerate aging.

– The Shift with Modernity: When we compared the pre-industrial period to the time after the onset of fertility control in the late 19th century, some patterns changed. For example, the number of surviving children became a more significant factor in the later period, likely due to lower child mortality rates meaning mothers spent more years actively raising their offspring. Notably, the negative impact of having children very early or very late seemed to lessen after the fertility transition, possibly due to changes in family planning and improved healthcare. The reduction in the overall reproductive period in more recent times appears to have been a key factor in improving women’s longevity.

– Nature vs. Nurture: We also considered whether these patterns could simply be due to inherited traits – perhaps long-lived women came from long-lived families and had fewer children due to genetic or culturally transmitted behaviors. However, even after accounting for the longevity and fertility of the women’s parents, our core findings remained consistent. This strengthens the idea that there was indeed a trade-off between fertility and longevity driven by the biological costs of reproduction.

Implications for Today

While our study focuses on historical populations with vastly different living conditions and healthcare access than today, it provides a valuable long-term perspective on the fundamental biological trade-offs that women have faced. The dramatic increase in women’s lifespan in modern times is undoubtedly linked to factors like improved nutrition, healthcare, and, crucially, the ability to control fertility, allowing for greater biological recovery between pregnancies and a shorter overall reproductive window. Our research underscores the profound impact that reproductive decisions and environmental context have on women’s health and longevity across generations.

We hope this glimpse into our research has been engaging. We believe that understanding the historical interplay between fertility and longevity can offer valuable insights into human biology and the remarkable changes that have shaped our lives over the centuries.

Read the original article: Marco-Gracia, F.J., & González Esteban, Á.L. (2025). Live fast, die young, leave a good-looking offspring: longevity and reproduction tradeoffs in rural Spain (1536-1965). Evolution & Human Behavior, 46(2), 106673.