The Sexy Stench of the Opposite Sex’s Genes

Also posted to The Faster Times

There are many ways to attract potential sexual partners. Some animals show-off with elaborately choreographed song and dance routines, others entice through the display of brilliant coloration, and yet others forego personal flare and solicit the opposite sex by bribing them with food or real-estate. Although the methods utilized to attract mates vary widely, the drive to reproduce is hard-wired in all of life. The genetic compliment held by each organism extends its reach into the external world with aspirations of replication and conquest. According to some recently published research, females of one primate species use their nose to select those sexual partners hosting the most apt of these aspirant genes.

Generally speaking, the female gender of a species is often better positioned to be the ‘chooser’ when selecting potential sexual partners; they have the final say as to how far a relationship proceeds. Females are conferred the gift of mate-preference because they, unlike males, take on the costly biologic and energetic burdens associated with pregnancy and the rearing of young. In the natural world, toting around offspring and locating ample food-stuffs to feed those progeny represent liabilities to the mother. Because she endures these hazards, she is provided the opportunity to decide with which males to mate. But given that females are the ‘deciders,’ on what grounds are their mate-selections made, and what criteria do they weigh and measure prior to committing to a costly reproductive venture?

‘Choose, but choose wisely’ is the mantra of the discriminating female when seeking-out male suitors. Through selecting only the most fit, well-matched mates, females are able to reap the benefits of their own inclusive fecundity and be better enabled to garner the evolutionary dividends of more numerous and healthy offspring. In regards to the beastly species known as Homo sapiens, human fertility clinics can utilize modern molecular techniques to perform genetic assessments; however, ‘good genes’ typically aren’t identified by non-human kinfolk in laboratory settings. Rather than admission to fertility clinics, in the wild evaluation of mates is undertaken on the fly using an organism’s innate sensory capabilities.

In its simplest form, avoidance of certain physiological cues such as developmental deformities can aid a female in filtering-out unworthy genetic sets. Unusual appearances, irregular gaits or abnormal vocalizations of male callers tend to stand-out to females and are almost always avoided. In other cases, elaborate courtship rituals, male-to-male fighting or induced ovulation tactics may be summoned into play as means of determining the superlative mate. Some primate species, like the mandrill for example, use their nose to guide their choice of sexual partners.

Mandrills are a variety of Old-world monkeys that inhabit parts of Equatorial Africa. They are highly social primates and can be found living in troops consisting of more than 1000 individuals. Recent research conducted jointly by scientists from the United Kingdom, France and Gabon suggests that the female mandrill is able to read the genome of potential mates through her nose. Because the male mandrills don’t offer anything to the females as a direct benefit – like the before mentioned tactic of bribing with food – the females endeavor to mate with those males possessing different, though complimentary, genetic characteristics.

By reproducing with partners holding diverse genomes the female improves the robustness of her line’s immune system. More specifically, the major histocompatibility complex (MHC) is a multi-gene family found within the genome of vertebrates that plays a key role in facilitating the immune system’s response to disease. Basically, by possessing greater diversity in the MHC, an animal’s immune system is more enabled to combat a larger range of foreign proteins. Through reproducing with male mandrills having a differing MHC, the female mandrill enhances her offspring’s capacity to thwart illness and disease. This ability to stave sickness is critical for an animal that resides in a hot, wet habitat with an abundance of bacteria and parasites. As stated previously, she distinguishes diverse MHCs through application of her olfactory apparatus – her sense of smell.

Male mandrills attract the females by rubbing their scent-glands against trees and rocks throughout their home territory. This effectively publicizes their MHC for the female’s review. If after assessing the male’s advertised MHC the female determines that the male possess sufficiently aspirant genes, she will choose him as a sexual partner.


SETCHELL, J., CHARPENTIER, M., ABBOTT, K., WICKINGS, E., & KNAPP, L. (2009). Opposites attract: MHC-associated mate choice in a polygynous primate Journal of Evolutionary Biology DOI: 10.1111/j.1420-9101.2009.01880.x

Photo Courtesy of Joyrex