Importance of Male Muscularity in Mating Process

From the perspective of evolution, basically, everything we have seen on different species today has certain reasons that lie in the process of natural selection which has continued today since the dawn of time. Although from pure appearance, we human is not much more special or complicated than any other animals, in the realm of behavioral sciences, we most certainly are due to our more advanced social and behavioral practice that came right alongside our intellectual superiority. Of all those human behaviors, I’m particularly interested in mating behavior, because it has a close relation to the most foundational step in human evolution: sexual selection.

Why women commonly enjoy men’s muscularity? As simple as it looks like, there is actually a lot to process before answer this particular question. There have been many studies about the pattern of human mating, especially the traits or characteristics that we seek from the opposite sex (I rule out the homosexual case due to minimizing the complexity of the research). For many years, the mainstream study has focused on what males want on females, explanations of one specific trait that males care for certain reasons. Such emphasis exists largely due to comparing to female, the male preference on females generally more closely relate to their cues of fertility, which makes these studies can eliminate the disturbance from other more complicated factors.

In contrast, the male attributes that work in the mating environment have been widely considered as more of commitment and the ability to provide resources, and less about physical attractiveness (Frederick and Martie, 2007). However, since the assignment of this essay is aiming at human behavior rather than pure evolutionary biologic analysis, it’s not a terrible idea to analyze the reason for women’s preference for men and not vice versa.

There are many things that women want on men, and because of our advanced social dynamics, these requirements are not only massive on quantity, but also on the level of complexity. Therefore, for research to find the foundational drive behind all these desires, then the procedure of putting these demands into categories would be necessary.

Firstly, there are many researchers consider human mating pattern into two different modes, one is short-term mating, another is long-term mating. This classification of the time period is necessary because women have been observed having different needs under different scenarios (Buss, David M, 1994). The classification of short and long-term mating is important also because this system determines the subsequent traits that women demand from men, including the main focus of this essay, muscularity. For us to understand the full function of a particular trait, we must examine them under the framework of short and longterm mating.

Buss, David M. The Strategies of Human Mating. American Scientist 82, no. 3 (1994): 238-49. Figure 2
Buss, David M. “The Strategies of Human Mating.” American Scientist 82, no. 3 (1994): 238–49. Figure 2

From the perspective of women in the most time of human civilization, a male partner’s function except procreating shall be the ability to provide both resources to women and parenting help to the offsprings. A short-term relation although can satisfy the need for sexual intercourse, can’t provide much help for the latter. Therefore, between the two types of mating, the female has been observed favoring long-term relation by a significant margin, which is supported by an actual experiment conducted in a cross-cultural context under the method of interviewing and surveying (Buss, David M, 2016). For women in a short-term relation, they do not desire a “the more the better” male quantity since the increasing male sexual partners do not increase their chances to produce more offspring.

Therefore, compare to males, females are more selective in sexual partners, and such behavior will most certainly affect the requirements that women list for men. Because the relation is short-term, then the female will unlikely demand male to invest parentally in offsprings, therefore the commitment of male long-term resources provision will be in low priority. And regarding this immediate resource, it can be food, shelter, money, and also, protection would translate into several characteristics that a male shall possess: financial status, physical dominance, and willingness to provide these resources to his sexual partner. What about long-term relations? Although the genetic advantage is still important, the focus, however, changed to the side of commitment. The ability and willingness to provide longterm resources is the most important characteristic of a male to female in a long-term relationship. Moreover, the importance of physical prowess shall decline even more in a long-term relationship if we consider the perspective of a male. If a male has a dominant physical or genetic edge, the best interest of his from sexual selection degree would be to spread his gene as much as possible, and he can actually achieve such a goal by committing many short-term relations and avoid long-term relationships due to minimizing his parental investment. Therefore, on average, to the same female, the male she accesses to in short-term relation is likely to be genetically superior to the male she committed long-term relationship with. Such a pattern has been observed in many different pieces of research (Buss, David M, 1990)

Finally, we can start to analyze muscularity itself after we built up the context. As the figure is shown above, women in both types of mating desire the male partner to possess gene as good as possible, and for this single request along, why muscularity has shown attractiveness? How is it an edge in the process of sexual selection?

First, is muscularity a fitness cue among human males? Before I studied evolutionary biology, my guess to this question is that muscular men can protect better, and can also represent a better earning potential in an agricultural society. From the degree of morphology, some species could evolve some heavy metabolically occupied traits as long as it helps to attract the opposite sex, like the peacock. If we classify muscularity into this category (extra muscle is indeed hard to maintain), then we shall explain it like the beautiful tail of male peacocks. (Zahavi, 1975) In that way, the muscular body (or facial characteristics) shows that the male is in a good condition that has extra energy to generate and maintain such features. Moreover, Ono the idea of “muscularity is a sign of fitness”, there is also research that shows averagely muscularity decline our immune system (Folstad, Ivar, 1992), and since disease damage an individual’s muscularity, so if a male possesses a strong body, it means he maintained healthy even with relatively weaker immunity, then he shall be considered in a good condition.

However, just like the naive version of me thought about before, a muscular body can do more than the tail of the peacock, it’s unfair to only classify it as a display trait. For a very long period of time, the male who possesses a strong body is indeed appreciated among not only females, but male and the rest of society, and thusly more likely to have higher social status and resources. In this case, women in both types of mating patterns can benefit from a relationship with these men, and therefore increase their selective edge over the rest of men. For both short and long-term seeking females, one of the ways that they pursue reproductive success is to increase their offspring’s advantage in sexual selection. Therefore, to determine the heritability of muscularity will be important for knowing how much females desire such a trait. Based on the research of Thomis and Beunen’s (1998) experiment, “One twin study assessing gains in strength across a 10-week training period also found that the ability to add muscle mass beyond one’s baseline degree of muscularity is heritable”, if so, then it will be natural of the result we saw earlier in Prof. Buss’s experiment.

Is there any difference between women’s desire for men’s muscularity between short and long-term relations? Men who possess superior muscularity, need to secure such an advantage by seeking more sexual partners and pass down the DNA while limiting their investment in parental care. And if the term reverses, the men who do not have such an edge should best be focusing on a single companion, and invest in his offspring (Gangestad & Simpson, 2000). Therefore, for women who are looking for a long-term relationship, the muscular men are less likely to invest their resources to the offsprings, and also more likely to commit cheating, and both of these tendencies conflict with the foundational desire of women who are seeking a long-term relationship. Therefore, for women, the attractiveness of male muscularity differ between short and long term relations.

However, if muscularity is only highly desirable in short-term relations (it’s of course still desirable in the long-term, just not so much), why the women today, still consider it in high priority? For this question, I have a hypothesis: between a muscular male and a normal male (they are identical in other ways), although they both can have compatibility in different types of relations, the muscular male is likely to have sex with more people than the normal male, and therefore even the muscular man’s offsprings lack parental care (relatively), he still has a bigger reproductive success, thusly can increase the frequency of his gene in the next generation.