Microchimerism is a term that refers to the phenomena of cells or genetic material from another organism being present and integrated into a certain organism's body. Specifically, when referring to humans, it refers to the idea that women's bodies are infused with the DNA of their previous male sexual partners (that they engage in unprotected sexual intercourse with), or their male offspring (carried to term fully or not). It has been speculated that this male DNA or RNA could therefore influence the traits of their subsequent offspring, and could possibly also influence the women's own phenotype. The evolutionary advantage would be that the genes would replicate in a different organism thus increasing reproductive success via a separate pathway than direct fertilization of the egg cells.
Microchimerism are a contentious and taboo concept in humans, especially when linked to claims that unprotected sexual intercourse as a source of male chimerism in females. It is often derided as long debunked pseudo-science as the idea is roughly equivalent to the ancient concept of telegony. New research seemingly demonstrating that male semen is a potential source of microchimerism and possibly telegony in humans, however, has lead to a resurgence of interest in the topic.
Brief history of the concept[edit | edit source]
The idea of telegony was first formally developed by the Greek Philosopher and proto-scientist Aristotle (the idea that females and their offspring acquire traits from the mother's prior sex partners, particularly the mother's first). The concept was also well known to animal breeders throughout history,and the father of modern evolutionary theory, Charles Darwin, proposed a theory of telegony mediated by sperm molecules. The philosopher Otto Weininger briefly mentioned telegony in Sex and Character as being caused by the overwhelming influence a woman's "absolute sexual complement" exerts on her when she engages in intercourse with him.
Evidence[edit | edit source]
There have been scarce studies validating the concept of sexual intercourse resulting in the microchimerism of male DNA and RNA in the female body. This area represents a relatively novel field of research, that is likely being hindered by the potential political and social implications of this phenomena being common in humans. A brief overview of some of the relevant research into the matter follows:
- Jørgensen et al. (2012), examined (n=272) female participants in a seperate Danish longitudinal dietary study for evidence of male microchimerism. They commented: "We assumed male microchimerism to originate from pregnancies with a male fetus. Contrary to what we expected, we found no obvious association between the number of live-born boys and detection of male microchimerism." They stated that: "Also, a prior study of male microchimerism and breast cancer by Gadi et al. reported 33% of healthy control women without sons to test positive." They left the question open regarding the potential sources of this male chimerism in their female subjects, writing: "Although not yet studied, sexual intercourse without pregnancy has also been hypothesized as a source of male microchimerism. Information on sexual habits was not collected in this study, which is why we could not pursue the possibility that either current or past sexual activity could predict male microchimerism positivity."
- Chan & Nelson (2013) utilizing the technique of real-time polymerase chain reaction, found that 63% of the women in their sample exhibited male microchimerism. They also found a very tentative link between this male chimerism and Alzheimer's disease, concluding "We found brain Mc (microchimerism) to be relatively frequent in humans and widely distributed in this organ. Our data also suggested a lower prevalence of brain Mc in women without Alzheimer disease than women without neurological disease."
- Müller et al. (2015) examined a cohort of young nulliparous (not having borne children) Danish girls aged 10-15 (n=154) and discovered evidence of male microchimerism in 13.6% of the sample. They found a higher likelihood of male chimerism in females whose mothers had received blood transfusions or had previously given birth to male offspring, but stated that only half of the male chimerism found could be attributed to these factors. They concluded: "We speculate that sexual intercourse may be important but other sources of male cells likely exist in young girls."
- Zagoskin MV, Davis RE, & Mukha DV (2017) studied the semen samples of 'three 30 year old men' and found: "We have shown that human seminal plasma contains a repertoire of cell-free dsRNA. We do realize that the identity, source, and functioning of these dsRNA are yet undetermined. We hypothesize that these dsRNAs could influence the implementation of genetic information or gene regulation in offspring." They also speculated, based on the previous research by Crean et al. (in fruit flies), that nucleic acids found in human semen, may possible penetrate in the immature oocytes (egg cells) found in the women's ovary, and therefore potentially allow the women's subsequent offspring to inherit characteristics of her prior male sex partners, writing "We suggest that one of the possible functions of dsRNA in human seminal plasma may be to influence human oocytes and therefore, influence the offspring. They called for more research to be performed on the subject of telegony, (e.g. in other mammalian species such as dogs).
- Crean et al. (2014) conducted a study that demonstrated the existence of telegony in flies (Telostylinus angusticollis) finding: "Although the second male sired a large majority of offspring, offspring body size was influenced by the condition of the first male". They concluded that this finding of non-parental genetic transmission had important implications for evolutionary theorists: "The potential for such effects exists in any taxon characterised by internal fertilisation and polyandry, and such effects could influence the evolution of reproductive strategies."
Potential Implications[edit | edit source]
If microchimerism transferred through the emission of semen, thereby resulting in telegony was proven to exist in humans, it would demonstrate that there are very tangible and lasting consequences to unrestricted female promiscuity. Some women however, see the concept of telegony as arousing and amusing—it would mean that their prior desirable sexual partners have potentially left a permanent impression upon them and their offspring. Men would also potentially become jealous at the likelihood of being 'micro-cucked' by their wives or girlfriend's prior sexual partners.
Traditionalists also frequently use the purported existence of telegony as a rhetorical point to emphasize what they view as the strong drawbacks of widespread female sexual license. The concept is cited by some traditionalists as evidence that women that aren't virgins are irredeemably "tainted", and they claim that the concept, if validated, proves the wisdom of traditionalist practices that insisted (and still do in some regions) on the virginity of the woman before marriage. The concept is apparently promoted in Traditionalist Russian Orthodox circles, with the current Children's Rights Commissioner for the President of the Russian Federation, Anna Kuznetsova, being an outspoken prominent proponent of the theory. Though she backtracked somewhat when she was subjected to widespread vituperation due to her views on the subject.
There is also tentative evidence possibly linking male and fetal microchimerism to a host of health problems, including: Auto-immune disease (increased risk only found after "induced abortion"), increased risk of certain cancers (though it may actually be associated with increased chance of surviving certain cancers), and evidence linking greater levels of male chimerism in the female brain with Alzheimer's disease.
The concept—if validated—would also be of interest in the fields of evolutionary biology and evolutionary psychology, since it would possibly be a factor in explaining the male urge to 'mate-guard', and would potentially also influence the reproductive strategies pursued by organisms of either sex. It would likely also be of interest to those in the field of medicine and psychology, as the male chimerism (found in the brain) may potentially influence the psychology and therefore behavior of the females who have been chimerized.
Theoretically, it could also be possible to discern a women's number of prior sexual partners (that she had unprotected sexual intercourse with) through examining her DNA for signs of male microchimerism, and extrapolating the total amount of male chimerism in her genome.
References[edit | edit source]