A new study found that men and women infected with the brain-hijacking parasite Toxoplasma gondii are rated more attractive and look healthier than their non-infected counterparts.
This microscopic invader can infect anyone and is even believed to have already infected 50% of the whole population. It is best known as the parasite that alters the behavior.
However, the new study shows that it also changes the phenotypes of people that are making them look more attractive and symmetrical.
T. gondii's Unusual Benefit
From an evolutionary biology standpoint, scientists claim that the findings of the study, titled "Are Toxoplasma-Infected Subjects More Attractive, Symmetrical, or Healthier Than Non-infected Ones? Evidence From Subjective and Objective Measurements," published in the journal PeerJ make sense.
Researchers hypothesize that the parasite may occasionally benefit infected animals and perhaps people by helping spur its own transmission prospects, Science Alert reported.
The study's first author Javier Borráz-León, a biologist from the University of Turku in Finland, cited a 2011 study in which male rats with toxoplasmosis were perceived to be more sexually attractive and preferred as sexual partners by non-infected females.
The finding could also be related to human cases of toxoplasmosis in which infected men tend to have higher testosterone levels than non-infected men. Researchers noted that men with higher testosterone are also more likely to be infected in the first place.
But it could also be viewed that the parasite may be altering the phenotype of its host and manipulating the chemicals in the body, such as neurotransmitters and hormones. Borráz-León and his team suggest that some sexually transmitted T. gondii may produce behavioral changes due to the infection.
Furthermore, women infected with the parasite tend to have lower BMI and are perceived to be more attractive. They also have a higher number of sexual partners.
The parasite may have produced changes in the facial symmetry of its hosts by changing their testosterone levels. Also, the parasite could have influenced the metabolic rate, which enhances the perception of beauty and health.
T. gondii Might Be Changing Fear Into Sexual Attractiveness
When T. gondii infects rats, they turn the rodents into fearless animals with a reduced natural aversion to the odor of cat urine. According to NBC News, the 2011 study also hinted at how toxoplasmosis in rats could strangely turn fear into sexual attraction.
Researchers wrote that infected who were once afraid of the smell of cat urine now activate the part of the brain responsible for controlling sexual attraction, which spurs the animal to approach the odor instead of running away.
When they analyzed the brains of infected rats to non-infected rats, they found that the fear pathway is still working and shows signs of activity. But it also activated the sexual attraction pathway, which shows that sexual drive has trumped fear in the rats.
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