🐣 When giving life reduces one's own life expectancy

In Japanese quail, a biological trade-off creates a cost to motherhood. Producing more for one's chicks accelerates aging and shortens lifespan.

The study, published in Proceedings of the Royal Society B, is based on an experiment. Researchers from the University of Exeter selected quail lines capable of laying either large eggs or small ones. In this species, parental effort is limited after hatching. The bulk of the maternal investment is concentrated on egg production.


Over five to six generations, the differences become marked. Females producing large eggs give birth to more robust chicks with better survival chances. But this biological generosity has a measurable price.

The scientists observe that these females age more rapidly. Their life expectancy drops by about 20% compared to those laying smaller eggs. On average, they live 595 days, compared to 770 days for their less invested counterparts.

This result illustrates an old idea in evolutionary biology. Every organism has limited resources. The energy devoted to reproduction cannot be used for the natural maintenance of the organism, such as cellular repair or immune defenses.

According to the authors, this link between reproductive effort and aging remained difficult to demonstrate experimentally. The selection approach used here provides direct proof. It also shows that these two traits, reproduction and longevity, are linked.

Previous work had already suggested underlying mechanisms. Quail that invest heavily in their eggs show less efficient cellular repair and a weakened immunity. These weaknesses could accelerate the body's wear and tear.

Males, on the other hand, generally live longer. The experiment did not, however, last long enough to clearly establish the effect of this selection on their longevity. Their limited role in reproduction, in this species, could explain a different biological pressure.

These observations go beyond the case of birds. They show a general principle of living things: reproduction is never free. Behind every reproductive strategy lies an evolutionary trade-off between transmitting life and preserving one's own.