Saumya Pandey
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Written By: saumya pandey | Updated : December 11, 2023 9:01 AM IST
Reproductive behaviors have played a significant role in these demographic transformations.
In 1957, evolutionary biologist George Williams proposed the antagonistic pleiotropy theory, suggesting that genetic mutations promoting earlier reproduction could be favored by natural selection, even if they contribute to aging. The antagonistic pleiotropy theory posits that certain genetic mutations, beneficial for reproduction early in life, may also contribute to the aging process. A recent study led by U-M evolutionary biologist Jianzhi Zhang revisits this theory. The study not only offers substantial genomic support for the antagonistic pleiotropy theory but also underscores the dynamic interplay between genetic factors and environmental influences in shaping the trajectory of aging and reproduction in human populations. The study's findings are contextualized within the broader shifts in human demographics. Contrary to genetic influences, recent trends in declining birth rates and increasing life expectancy are predominantly attributed to environmental factors. Lifestyle changes, technological advancements, and shifts in reproductive behaviors emerge as the driving forces behind the transformative demographic landscape.
People involved in the study used data from the UK Biobank database, including genetic, reproductive, and death-registry information from over 276,000 participants. The study found a strong genetic negative correlation between reproduction and lifespan, supporting the antagonistic pleiotropy theory at a genomic scale. It identified that individuals carrying mutations promoting higher reproductive rates tended to have a lower probability of living to age 76 compared to those with mutations favoring lower reproductive rates. This supports the idea that genetic mutations influencing reproduction may impact lifespan.
The study emphasizes that both reproduction and lifespan are influenced by genes and the environment. However, genetic factors play a relatively minor role compared to environmental factors, including contraception, abortion, and medical advances. The research underscores that natural selection prioritizes fitness by the end of reproduction.
Examining 583 reproduction-associated genetic variants, the researchers found that variants linked to higher reproduction have become more common, despite their association with shorter lifespans. This aligns with the antagonistic pleiotropy hypothesis, suggesting that mutations favoring higher reproduction may have larger fitness advantages than disadvantages.
Despite genetic factors, the study highlights that recent human demographic trends, such as declining birth rates and increased life expectancy, are primarily influenced by environmental shifts. Lifestyle changes, technological advancements, and global shifts in reproductive behaviors have played a significant role in these demographic transformations.
While the study provides genomic evidence supporting the antagonistic pleiotropy theory, it emphasizes the crucial role of environmental factors in shaping human demographic changes. The contrast between genetic influences and environmental shifts underscores the dynamic interplay between evolution, genetics, and changing lifestyles in human populations.
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