In a twist of evolutionary paradox, a study suggests genes promoting earlier childbearing come at a cost: a shorter lifespan. Analyzing 270,000 genomes, a University of Michigan-led study found a link between genes for early parenthood and a lower likelihood of reaching 76. This challenges the classic view of natural selection favoring longevity for more procreation. Instead, the culprit might be "antagonistic pleiotropy," where genes giving early reproductive advantages also shorten life. This discovery adds a fascinating wrinkle to the aging mystery, suggesting that nature's trade-offs can be surprising and complex.
As per a release, the University of Michigan's evolutionary biologist Jianzhi Zhang and a Chinese colleague tested the Williams hypothesis using genetic, reproductive, and death-registry information from 276,406 participants in the United Kingdom's Biobank database. They found reproduction and lifespan to be genetically strongly negatively correlated, meaning that genetic mutations that promote reproduction tend to shorten lifespan.
In addition, individuals carrying mutations that predispose them to relatively high reproductive rates have lower probabilities of living to age 76 than those carrying mutations that predispose them to relatively low reproductive rates, according to the study.
The link between early childbearing and a shorter lifespan, while intriguing, doesn't paint the whole picture. The authors acknowledge that both genetic predispositions and environmental factors, including contraception, abortion, and healthcare access, shape reproductive choices and lifespans. Understanding this complex interplay is crucial to unraveling the aging mystery.
"These results provide strong support for the Williams hypothesis that aging arises as a byproduct of natural selection for earlier and more reproduction. Natural selection cares little about how long we live after the completion of reproduction because our fitness is largely set by the end of reproduction," said Zhang, the Marshall W. Nirenberg Collegiate Professor in the U-M Department of Ecology and Evolutionary Biology.
