Health experts have often discussed sex and its effects on human health. In their attempt to understand the effects of mating on health and lifespan in females, a study was carried out in an animal model. A general practice in science is to use animal models as study organisms and rats, monkeys and other mammals are often used as subjects of laboratory experiments.
In an article published in the top-tier journal Science, it was concluded that males of C. elegans, a soil roundworm, significantly shortened the lifespan of the opposite sex, both by mating and through secretion of bodily fluids. A previous study reported similar findings in Drosophila, a fly genus, which concluded that proteins in the seminal fluids of males shortened the female life span.
So, how can it be possible?
How can sex and/or reproduction adversely affect an organism's health? Aren't they critical to the survival of a species? Isn't it potentially anti-evolutionary for sex to accelerate death? Well, the authors of this study propose that this might in fact be an evolutionary strategy, adopted by male organisms to shorten female life span, in order to save on limited resources for the next generation. The hypothesis may take longer to prove, but the experimental facts cannot be denied.
Some interesting experimental observations:
- Males induced the signs of old age in female worms. Both behavioral and physical changes were seen, including lethargy, weakness and signs of cellular aging.
- A 20% decrease in the life-span of female in the presence of mating males. The scientists called this phenomenon as "Male-induced-demise" - (MID).
- Sterile females who mated with males, also showed a decreased life span, showing that reproduction related physical changes are not necessarily a cause of decreased life term.
- Upon careful genome-expression, it was found that mated females showed significant changes in the gene expression against their non-mated counterparts. The health deteriorating and age inducing factors were enhanced in females that underwent copulation with the males.
The scientists also created an interesting scenario, wherein mating wasn't allowed but the females were subjected to an environment in which males secreted their bodily fluids and hormones. Interestingly, these females also showed a shortened life span. It was concluded that both the presence of sex hormones/biochemicals which could diffuse into the female body from surroundings and mating-induced seminal discharge from males into the females act as contributing factors toward the shortened life term. Mating seems to enhance the efficiency of the whole process. As it is, the "sperm" by itself has been ruled out as being responsible for this observation.
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