The life history theory suggests that there exists trade-off between life processes like reproduction and growth and maintenance of the organism.

One significant trade off is between somatic effort (towards growth and maintenance of the body) and reproductive effort (towards producing offspring).

Quoting from wikipedia page Cost of reproduction hypothesis

The traditional view of the cost of reproduction says that a cost is caused by differential allocation of limited internal resources. (...) Reduced immune function and a decreased defense against environment stress are also important factors in the cost of reproduction.

It has been suggested that this kind of trade-off in resource allocation between different life processes has plasticity, that is, the resource allocation between different life processes in a given individual is dependent upon external factors like the absolute amount of nutrient input.

Reduced nutrient availability can substantially magnify, while increased nutrient availability can diminish or obviate an apparent trade-off. (...) For example, in laboratory and field experiments on bivalves, cladoc- erans, insects, and mammals, allocation to maintenance or storage was found to take precedence over allocation to reproduction under nutrient-poor or stressful conditions

So, my question is, what does all this mean? Could sexually inactive life for an organism, for whatever reason, actually correspond to longer health span? (Better immunity, growth and maintenance of the body, etc.)

I know that the rate of deterioration of health with age is hugely determined by the rigid parameters corresponding to the specie the organism belongs to. But for a given organism, the various life processes like reproduction, repair and maintenance, and immune system are fighting for the limited resources available, and it appears that there is some amount of plasticity in how much resource will be allocated to which life process. In other words, the rate of deterioration of health of an individual appears not to be completely written on stone.


1 Answer 1


I am not sure if life span could be extended in such circumstances but the probability of survival could probably increase, given the high metabolic costs of growing and raising offspring. I work mainly with marine mammals and there are multiple studies showing that the body condition of females following births is much lower (as to be expected), and thus health indices are worse. Therefore, these animals are at greater risk of being severely affected by infections or variable densities of available prey, showing to an extent the high costs of reproduction.

Another thing to consider is the level of stress that any member of the population is exposed to. Whether an individual is sexually active or not, various stressors (i.e., limited prey, pollutants that compromise the immune system) can limit their life span and increase mortality risks. For example, there are various studies on the effects of persistent organic pollutants such as PCBs (i.e., https://pubmed.ncbi.nlm.nih.gov/29096314/) that can be passed down to calves and persist in the body for long periods of time. These substances can compromise the immune system, thus putting animals with high concentrations of these pollutants in their bodies at greater risk irrespective of whether they become sexually active or not. Therefore, there might be a higher likelihood that an animal can live (potentially) longer as a result of the lack of investment in reproductive activities, because the resources can indeed be used for growth and body maintenance, but there are stressors that can limit survival rates before the animals are even born. Here is a study that is not directly related to the cost of reproduction, but investigated the plasticity of immune investment in individuals exposed to human-generated stressors and limited food availability: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0067132

I hope this answers your question and if you are interested in references to papers that were briefly mentioned but not specifically provided, I am happy to help!

  • $\begingroup$ You bring up an important factor with the human generated chemicals likely to contaminate much of what's currently likely to be observed. $\endgroup$ Apr 19, 2022 at 12:24
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    $\begingroup$ I wonder if this also relates to matriarchal societies needing their matriarchs to survive longer (to lead, pass on knowledge, etc) and menopause/cessation of female fertility? $\endgroup$
    – Shannon
    Apr 19, 2022 at 13:07
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    $\begingroup$ Also keep in mind that females can offload contaminants to offspring via gestation and lactation, therefore reducing the contaminant load of the mother. But whether or not reduced contaminant loads offset the energetic demands of motherhood is another question... $\endgroup$
    – ASimonis
    Apr 20, 2022 at 16:03

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