New Findings on Senescence and its Evolutionary Advantages

Evolutionary biologists at the HUN-REN Centre for Ecological Research, led by Eörs Szathmáry from the Hungarian Academy of Sciences and including András Szilágyi, Tamás Czárán, and Mauro Santos, used a computer model to demonstrate that under specific conditions, senescence can aid in responding to directional selection and facilitate adaptation to changing environmental factors.

New Findings on Senescence and its Evolutionary Advantages

Image Credit: Hungarian Academy of Sciences.

Their study, published in BMC Biology, sheds light on senescence, showing it is not solely a detrimental outcome of natural selection but can actually benefit organisms. This breakthrough marks significant progress in unraveling senescence, a long-standing challenge in evolutionary biology.

The age-old fascination with the mystery of aging persists, driven by the desire to impede or reverse the gradual decline in various bodily functions associated with aging. Despite being a natural facet of life, the emergence of senescence during evolution remains poorly understood among biologists.

The inevitability of aging is unclear, as some organisms seemingly defy aging altogether. Furthermore, the existence of negative aging or rejuvenation is evident in certain species, such as turtles, whose vital functions improve with age.

Researchers at the Institute of Evolution, led by Academician Eörs Szathmáry, have undertaken the task of substantiating a previously proposed yet unverified theory of aging. This theory posits that, given the right conditions, evolution can favor the proliferation of genes that regulate senescence.

To assess the hypothesis, the scientists employed a computer model that they had crafted. This algorithm possesses the capability to simulate extended processes within populations of organisms and genes, operating under controlled conditions set by the researchers.

Essentially, these models enable the execution of evolutionary scenarios, producing outcomes within a matter of hours rather than spanning millions of years. Contemporary evolutionary research heavily relies on computer modeling.

The core inquiry of the study was straightforward: Does aging hold any significance? Does it fulfill an evolutionary purpose, or is it truly a harsh and inevitable byproduct of life??

Aging can have an evolutionary function if there is a selection for senescence. In our research, we aimed to uncover this selection. According to classical explanations, aging emerges in the populations even without selection.

Eörs Szathmáry, Member, Hungarian Academy of Sciences

Szathmáry added, “That is because individuals would die sooner or later without aging as well (as a consequence of illness or accidents), therefore the force of natural selection in the population would get weaker and weaker.

This creates an opportunity for the genes which have an adverse effect for chronologically old individuals (thus causing senescence) to accumulate. Which would mean aging is only a collateral consequence of evolution and has no adaptive function,” continued Szathmáry.

Over the past century, various evolutionary theories have emerged to account for the seemingly unavoidable process of aging, attributing it to different biological mechanisms without a discernible positive function.

Initially accepted as a factual assumption by many scientists, the discovery of non-aging organisms has prompted an increasing number of researchers to challenge the inevitability of senescence. Instead, some suggest that aging might potentially harbor certain advantages.

It has become accepted in the evolutionary biology community that the classical non-adaptive theories of aging cannot explain all the aging patterns of nature, which means the explanation of aging has become an open question once again.”

Eörs Szathmáry, Member, Hungarian Academy of Sciences

Szathmáry added, “Alternative adaptive theories offer solutions for this problem by suggesting positive consequences of senescence. For example, it is possible that in a changing environment, aging and death are more advantageous for individuals, because this way the competition, which hampers the survival and reproduction of the more adaptable progeny with better gene compositions, can be decreased.”

Yet, this situation remains valid primarily when individuals are predominantly in proximity to their relatives. In cases where sexual reproduction occurs, non-aging individuals essentially “appropriate” the superior genes (better suited for the altered environment) from members of the aging population, leading to the attenuation of significant senescence.

Upon executing the model, Hungarian biologists discovered that aging can, indeed, expedite the process of evolution.

This proves advantageous in a dynamic environment, as accelerated adaptation facilitates the swift identification of suitable traits, thereby bolstering the survival and dissemination of descendant genes. Consequently, senescence can transform into a genuinely advantageous characteristic, garnering favor from natural selection.

Source:
Journal reference:

Szilágyi, A., et al. (2023) Directional selection coupled with kin selection favors the establishment of senescence. BMC Biology. doi.org/10.1186/s12915-023-01716-w.

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