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Definition: How do evolutionary theories explain the decline in fertility with age?

Evolutionary theories offer insights into the decline in fertility with age, providing explanations rooted in the principles of natural selection and reproductive success. These theories propose that the decline in fertility is a result of the trade-off between investing resources in reproduction versus investing in somatic maintenance and survival.

Antagonistic Pleiotropy Theory

One prominent evolutionary theory explaining the decline in fertility with age is the antagonistic pleiotropy theory. According to this theory, genes that enhance reproductive success early in life may have detrimental effects on health and fertility later in life. These genes are believed to have evolved because they confer a selective advantage during the reproductive years, despite their negative consequences in later life stages.

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Disposable Soma Theory

The disposable soma theory suggests that organisms have a limited pool of resources available for allocation between reproduction and somatic maintenance. As individuals age, the resources allocated to somatic maintenance, such as repairing cellular damage and maintaining organ function, become prioritized over reproductive investment. This prioritization leads to a decline in fertility as resources are diverted away from reproduction.

Grandmother Hypothesis

The grandmother hypothesis proposes that menopause and the decline in fertility with age are adaptive strategies that enhance the survival and reproductive success of offspring. According to this hypothesis, post-reproductive females can invest their resources in supporting their existing offspring and grandchildren, increasing their survival and reproductive success. By ceasing reproduction themselves, older females can allocate resources more effectively, ultimately increasing the fitness of their genetic lineage.

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Conclusion

Evolutionary theories provide valuable insights into the decline in fertility with age. The antagonistic pleiotropy theory suggests that genes favoring early reproductive success may have negative effects on fertility later in life. The disposable soma theory highlights the trade-off between reproductive investment and somatic maintenance. Lastly, the grandmother hypothesis proposes that menopause and decreased fertility in older females are adaptive strategies that enhance the survival and reproductive success of offspring. These theories collectively contribute to our understanding of the evolutionary basis for the decline in fertility with age.

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Keywords: fertility, reproductive, decline, success, resources, evolutionary, reproduction, somatic, maintenance