A study published in the scientific journal Nature Communications has confirmed that men with strong, healthy immune systems, (and the physical qualities inherent therein), are typically deemed more attractive by members of the opposite sex.

The study, conducted at Scotland's Abertay University, concluded that classically attractive masculine traits — facial hair, a strong jaw and toned body — develop in conjunction with healthy testosterone levels, “due to the sex hormone's immunosuppressive action,” as written by the final paper's authors.

This means that men who produce adequate levels of the hormone are less likely to get sick and more likely to have the physical traits that make rugged, manly men types like Brad Pitt, George Clooney and Russell Crowe perpetually popular.

Researchers found positive relationships between testosterone levels, facial attractiveness and immune function in men. This research was done by injecting 74 Latvian men, all in their early 20s, with a shot of hepatitis B, which compromised the good health of the immune system.

Each man provided a blood sample immediately before the shot, and then again a month later. The men were each photographed, and the photographs were shown to 94 Latvian women of the same age group. These women were asked to judge each man's hotness on a scale of one to 10. Hotness ratings were then matched to each man's particular testosterone level and immune response.

Facial hair was linked with testosterone levels. Please make your own conclusions about this duo.

Facial hair was linked with testosterone levels. Please make your own conclusions about this duo.

The study found that men perceived as weak were less attractive and that high testosterone levels correlated with strong immune system responses and attractive facial features.

Researchers also found a link between testosterone, the immune system and the stress hormone cortisol. The connect here is that men with greater levels of cortisol (stress), have less healthy immune systems and lower testosterone levels, thus making them less attractive. Stress has long been known to compromise the immune system and manifest in flu, heart disease, thinning hair, teeth grinding, shortness of breath and a bevy of other decidedly unsexy symptoms.

The conclusion is pretty clear here: on a level of basic biology, women want to mate with a strong, healthy provider-man who can assist in the production of strong, healthy babies. What's significant is that women can detect such levels with the naked eye.

Oh, the gifts of animal instinct.

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