Romance among the Sexes: A Conflict of Darwinian Interests

Eveline was a tall, attractive, red-headed women, who loved to draw and read Shakespeare—a true romantic. And like many women her age, she came to college looking for love (the degree was a mere side-product), looking for the one chivalrous man who would save her from her loneliness, love her for who she was, and would spend the rest of life with her most willingly. And one day love came crashing into her—literally. It began with a bike crash, and ended in dinner. They dated for a while, went on glamorous outings to Chipotle, told each other of their dreams over Tuesday Dollar Scoop Nights, stayed up late at night telling each other secrets, and even named a few of their future children. Eveline could have sworn that she was in love, that she had finally found the one. That was, until he split. Disappeared—nowhere in sight. Such is the story told over, and over, and over again—countless tales of women looking for the one, countless tales of men looking for the many. Yes, it is a tragedy for those lonely romantics out there, but biologically speaking this behavior makes complete sense.

And just how does a broken heart and lack of a suitable mate make biological sense? Am I just making excuses for poor and inconsiderate behavior? It would appear counterproductive—energy lost over romance and love (energy that could have been used for finding food or running from predators), with no offspring to show for it. However, remember that there was a time when contraceptives did not exist, and polygamy, rather than monogamy persisted—a time that is currently still the present for many non-human groups.

From the very beginning of time, there has been a conflict among the sexes. This very conflict in romantic interests falls under the category of sexual selection, a sub-category of one of evolution’s mechanisms—natural selection. Douglas Futuyuma, an evolutionary biologist who has written a textbook on evolution, describes evolution as the “change in the properties of groups of organisms over the course of generations” (Futuyma 2005). In other words, the prevalence of specific physical characteristics change in a population over time. In human terms, this is like saying that the frequency of black haired people throughout the world has increased with time.

Charles Darwin, the founding father of the notion of evolution and natural selection, proposed that evolution occurred through a mechanism called natural selection. He noticed that, on a wide scale, organisms normally produce more offspring than can survive, and that there was variation among traits that were genetically passed on to the next generation. Because of these truths, Darwin proposed that organisms who have more favorable physical traits in their environment survive to reproduce, therefore passing their genetic material onto the next generation. Thus, as long as these physical traits are favored in the organism’s habitat, the offspring will survive to reproduce and pass on the genes again, thus increasing the frequency of the gene in the population.

So, how are natural selection and sexual selection different from each other? Darwin noted that while “natural selection depends on the success of both sexes, at all ages, in relation to the general conditions of life”, sexual selection “depends on the success of certain individuals over others of the same sex, in relation to the propagation of the species” (Darwin 1871). In other words, sexual selection is one of the many mechanisms in which natural selection persists, yet focuses on the differences in successful reproduction among the sexes and how this relates to the species as a whole. On the other hand, natural selection looks at successful reproduction in terms of the entire population. Yes, it is true that both males and females wish to reproduce with the common Darwinian interest of their genetic material surviving to the next generation. However, because “females produce relatively few, large gametes (eggs) and males produce many small gametes (sperm)”, males tend to want to release as many as their sperm as possible, while females tend to be quite choosey with whom they mate with (Futyuma 2005).

Let’s give this example context, and look at it in terms of walruses. Male walruses can mate with as many females as they wish, with the overpowering consequence of increasing the chances of their genetic material’s survival with each time that they mate. If the sperm does not make it to the female’s egg, it is not a large energetic loss; sperm cost relatively energetically little to make, so the notion that a single egg is fertilized far outweighs the loss of many sperm.

On the other hand, females make fewer eggs because they are energetically costly. Why waste one of her precious eggs on a male who will make her offspring less likely to reproduce? What if her potential mate is rather small and therefore has trouble keeping warm (ie. might die of frostbite)? What if his tusks are not large enough to defend his territory? Females get fewer chances at reproduction, so they make sure that they only mate with those with the best genetic material.

Alas, the female’s resulting pickiness often results in a phenomenon called “Runaway Selection”. If a female walrus begins to favor larger tusks because it indicates that the male is better suited to defend himself from potential aggressors (and thus has better genetic quality), she will mate with males who have larger tusks. Thus, males with overall larger tusk size will be introduced into the next generation, females mating with males with larger and larger tusks and therefore creating this continuation of increasing tusk sizes into future generations. However, what happens when these tusks are so large that it prevents the male from running away from predators, or finding food? An equilibrium is found between large tusk size and survival of males, so that both the goal of survival and mating can be achieved.

Sure, this all makes sense in polygamous societies (ie. walruses), but we humans are monogamous and have values, correct? Yes, and no. Let’s look at it this way: it would make sense for men to copulate with as many women as possible, as doing so would increase chances of their genetic material’s survival. Sure, society encourages monogamous relationships through the highly coveted values of marriage and faithfulness; however, society on some level also encourages the promiscuity of males, while condemning it in females. Famous male stars, such as Hugh Hefner and James Bond, are accepted, even glorified, in their attempts to mate with as many women as possible. On the other hand, famous female stars, such as Britney Spears and Lady Gaga, are looked down upon for their promiscuous and provocative ways—not idolized for the embracement of their sexuality like Hugh Hefner or James Bond, rather condemned for their immoral behavior.

Okay, so this attitude is prevalent in our society. But why and how? Is this just how society has formed over time or can it be explained biologically? Evolutionary biologists would argue that it is instinctual. As the descendants of winners, our ancestors have been very successful in the propagation of their genetic material. Since males who copulate with many females generally have a higher chance of passing on their material, we can confidentially say that we are the descendants of males who have followed such practices.

Now that I have thoroughly slashed your ideas of true love and romance with a conflict of Darwinian interests, let me give you something else to think about: Eveline did eventually find love. And he did not disappear. He did not split after a few weeks. And he even had large muscles, which make him the perfect mate in terms of genetic quality. They settled down, started a family, and relished in a completely monogamous relationship. Now, what does that tell you about the Darwinian conflict among the sexes? Perhaps Darwin is not completely 100% correct. Perhaps there is still hope for the hopeless romantics out there. Here’s to hoping.