Do mothers age faster? It depends on the context

Why do we age? From Aristotle’s musings about the body “drying up” to modern evolutionary theories, answers have swung between poetry and population genetics. 

Today’s leading idea, the disposable soma hypothesis, says aging is the trade-off we pay for reproduction.

Evolution prioritizes passing on genes, so energy spent on pregnancy, breastfeeding, and child-rearing is energy not spent repairing DNA, suppressing inflammation, or maintaining organs.

That logic should mean mothers who invest more in reproduction age faster. Yet, real world tests have given mixed results.

According to Elisabeth Bolund from the Swedish University of Agricultural Studies, it’s quite difficult to distinguish between correlation and causation, unless we have a large dataset covering several generations.

A natural experiment in hard times

Euan Young at the University of Groningen and colleagues suspected the confusion stemmed from a missing variable: the environment. Maybe the reproductive trade-off is elastic, i.e. masked in good times, glaring in bad ones. 

To test that, the team turned to a uniquely powerful record: parish books documenting more than 4,500 women across 250 years in Finland, including the catastrophic Great Finnish Famine of 1866–1868.

Those ledgers let the researchers line up lifespans, childbirth histories, and the timing of one of Europe’s worst 19th-century food crises with unusual precision.

Reproduction, motherhood, and aging

Outside the famine window, there was no meaningful link between family size and longevity. But among women who bore children during the famine, each additional birth shaved around six months off expected lifespan.

In other words, the cost of reproduction stayed invisible when resources were adequate, then revealed itself sharply when calories ran short.

These findings come close to identifying causation without devising a controlled laboratory experiment. Young’s team also ties the pattern to basic energetics: pregnancy and breastfeeding demand hundreds of extra calories per day.

During famine, the body can meet these demands only by decreasing basal metabolism, hence slowing or even shutting down other major  functions. This results in a decline in health and thus shorter lifespans.

The trade-off hides in modern life

That environmental dependence helps explain decades of contradictory studies. In many historical and low-resource settings, the trade-off shows up most clearly among women who were already stressed, malnourished, or repeatedly pregnant. 

In affluent societies, by contrast, the average reproductive burden has plummeted. Research in a Utah historical population suggests that clear longevity costs only appeared above five children.

That distinction may also help parse today’s longevity gap. Girls born in the UK between 2021 and 2023 can expect to live about four years longer than boys, and it’s tempting to chalk that up to biology alone. 

But lower reproductive costs for women today likely boost female life expectancy relative to the past, while lifestyle differences – men, on average, smoke and drink more – drag male life expectancy down. 

Mothers age faster under stress

The Finnish data doesn’t claim reproduction is the only driver of sex-specific aging. Genetics still matter, sometimes profoundly. Chromosomal differences likely play a role, too. 

That aligns with other recent demographic work from pre-industrial Quebec, where a similar trade-off appeared among mothers in poor health or under chronic stress.

Moreover, modern biomarker studies show how inflammation and nutrient scarcity push bodies toward short-term survival modes. 

Together, they sketch a consistent picture: evolution gave us flexible life history settings. When food is scarce or stress is high, mothers’ bodies channel what little energy there is toward offspring, even if that speeds their own decline.

What this means now

Motherhood doesn’t automatically come with a shorter lifespan – it depends on circumstances.

In places with good nutrition, strong prenatal care, and fewer pregnancies, the body has enough resources to repair and recover, softening or even erasing the usual trade-off between reproduction and longevity. 

Under duress – famine, chronic hardship, repeated pregnancies without recovery time – it becomes starkly measurable, as Finland’s 19th-century tragedy shows.

That nuance matters for policy and health. Supporting maternal nutrition, spacing births, and buffering families during economic shocks aren’t just “nice to have.” They’re levers that can literally reshape the aging curve for a generation of mothers.

And for scientists, it’s a reminder that big evolutionary ideas often hide in the details: to see the trade-off clearly, you have to look where life is toughest.

The study is published in the journal Science Advances.

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