A study conducted by the University of Michigan and published in the journal Science Advances has provided insights into the relationship between aging, genetics, and natural selection. The study focused on Williams theory, which was proposed in 1957, suggesting that genetic mutations associated with aging can be advantageous for natural selection if they expedite the reproductive process or increase offspring production at an early age.
In this research, more than 276,000 individuals from the British Biobank database were analyzed for genetic information and health data. The study revealed a strong negative correlation between reproductive function and life expectancy. Individuals with mutations that predispose them to have higher reproductive indicators are found to have a lower likelihood of surviving until 76 years of age compared to those with mutations predisposing to lower reproduction.
The researchers also discovered that genetic factors have a secondary role compared to environmental factors in influencing aging and reproduction. The impact of contraception and abortion on reproduction, as well as medical advancements increasing life expectancy, were identified as significant environmental influences. Nevertheless, the findings of the study support Williams’ hypothesis that aging is a by-product of natural selection, favoring early and abundant reproduction.
However, recent decades have witnessed substantial changes in human life expectancy, birth rates, and reproductive behavior, contradicting the changes expected from natural selection of genetic variations. These trends are primarily attributed to significant shifts in environmental factors, including changes in lifestyle and technology. For instance, the global average life expectancy has risen from 46.5 to 72.8 years since 1950.
The co-author of the article, Erping Long from the Chinese Academy of Medical Sciences and the Beijing Medical College, was a student at the University of Michigan when the study commenced. This study not only confirms Williams’ theory but also demonstrates the complex interplay between genetics and the environment in the process of human aging.