social sciences

Cheating from an evolutionary prespective

It often seems as if people want to create a division between men and women based on their behavior. And one of the much talked about aspects is relationships. I have been a part of several discussions on whether men or women cheat more on their significant other. From an evolutionary perspective, there is a lot to be said about the implications of cheating for men and women. 

However I’m not going to speculate on who cheats more, but the consequences of cheating for each individual. Buss, Larsen, Westen, and Semmelroth (1992) carried out a fascinating study on this topic. First of all, they address certain differences between males and females, which include pregnancy and parental certainty. In our species as many other species, females are at risk of getting pregnant through sex. So from that point on invest many resources in their offspring, whereas males can often easily abandon their offspring. Though the success of our species has been attributed to the fact that males throughout stuck around to care for their offspring (compared to other species, unfortunately this is not necessarily standard even in modern times). A problem for males is that they cannot be sure (without a DNA test) whether their offspring is genetically theirs.

Differences between men and women
All of these assumptions create a framework that can possibly explain jealousy caused by a cheating partner. As females find emotional cheating to be worse, whereas men can’t stand sexual cheating. Although I would like to point out that both sexes have issues with all types of cheating, there are significant differences in the degree of. These differences would have made a lot of sense in the Pleistocene era, the period of time when early humans transitioned to modern humans. The issue with emotional cheating for a female is that a male might get emotionally invested in another female. But for the offspring it would be beneficial for the male would be involved in their upbringing. Thus it would be problematic for the (pregnant) female to lose the parental investment from the male. For males it is a slightly different story, they seem to be more concerned with sexual cheating. The reasoning behind this is that the female could end up getting pregnant by a different male. And if a male were to be invested in offspring that isn’t theirs – he would be investing in survival and transfer of another individual’s genetics. This perspective is from a ‘selfish gene perspective’ in which a lot of strategies seemed to be based around the survival of one’s own genes through reproduction.

However not only do we invest in the survival of our own genes through reproduction, and making sure our offspring survives by caring and protecting them. We can also protect genes that aren’t in our offspring or in us, yet they are still ‘our’ genes as well. Our siblings approximately share 50% of our genes. This is because we get 50% from our fathers and 50% from our mothers, this seems to be the general rule. Though recent research has found that we might be getting just a little more from our fathers (Crowley et al, 2015). And following the same principle we share 12,5% of our genes with our cousins. Based on all of these assumptions were more likely to help out those we share genetic similarities with because it would guarantee survival of part of our own genes. This is referred to as kin selection, these heroic acts of saving relatives could even be in situations that decrease the chances of one’s own survival.

Issues with an evolutionary perspective
A lot is to be said about taking an evolutionary perspective. First of all, while some are convinced that we still carry the biologically programmed mechanisms that, for instance, make us feel jealous in certain situations, it is an oversimplification. There are many factors that influence our thoughts, behaviors, and emotions. And the current scientific paradigm does not propose genetic determinism, in the sense that genes are exclusively responsible for the aforementioned constructs. Environmental influences are known to influence these three major components as well, it is most likely an interaction between the two. Second of all, we no longer live in the Pleistocene era, we live in an epoch that comes after that, called Holocene. Although evolution takes a lot of time, we have several examples from the last 10,000 years. On example is lactase persistence, humans have become able to digest lactose, especially in certain regions in the world. These regions were involved in domestication of animals and consuming milk. This is referred to as gene/culture co-evolution, where culture and genetics are both susceptible to evolution and mutation. Third, in line with the previous argument, in many regions of the world, lifestyles have dramatically changed. Not only heterosexual couples take care of offspring, however this idea alone might have been an oversimplification for the Pleistocene epoch. Children are often looked after by many more or different people than (biological) parents.

Buss, D. M., Larsen, R. J., Westen, D., & Semmelroth, J. (1992). Sex differences in jealousy: Evolution, physiology, and psychology. Psychological science, 3(4), 251-255.

Crowley, J. J., Zhabotynsky, V., Sun, W., Huang, S., Pakatci, I. K., Kim, Y., … & Yun, Z. (2015). Analyses of allele-specific gene expression in highly divergent mouse crosses identifies pervasive allelic imbalance. Nature genetics, 47(4), 353-360.

social sciences

Sexual selection from an evolutionary prespective

Ask a couple why the choose each other and you probably get some story on how they thought their significant other was attractive. There are thousands of self-help books dedicated to helping you become more attractive. Even coaches exist to assist you in appearing appealing to the person of your liking. But what exactly makes people attractive? 

As suggested in the title, the following explanations are from an evolutionary perspective. This research field mainly seems to focus on heterosexual couples. Also, the first part of the theory will discuss physical attraction, the second part will look at personality characteristics. Hormones play a big role in secondary sex characteristics, which is essential in sexual selection. Men and women look at different cues that are important for reproduction.

Women look for characteristics that indicate high levels of testosterone, such as a broad jaw (Grammer & Thornhill, 1994). Such characteristics are the result of evolution through sexual selection. Because these indicate important physical traits to consider such as immunocompetence (the immune system being able to fight off antigens). These are favorable hereditary traits to pass on to your offspring. Yet another indicator of good genes is facial symmetry (Scheib, Gangestad, Thornhill, 1999). Which again, could be signaling good genes, as it could indicate development stability in puberty, the body withstood pathogens and perturbations (Gangestad & Thornhill, 2003). Ovulation can also influence females’ perceptions of attractiveness. As during this phase of the menstrual cycle, females prefer more masculine faces.

Men look for characteristics such as low hip-to-waist ratio since this could be an indication of good health (Sing, 1993). As for facial attractiveness, men seem to rate neonate faces as more appealing. These are faces with ‘young features’, such as big eyes or a small chin (Cunnigham, 1986). This could be due to the fact that women are fertile only for a certain period of time, which is linked to her younger years.

However, personality is still an important factor in attraction. Humor for one can influence people’s perceptions of attractiveness. Previous research has suggested that it displays intelligence. Li et al (2009) point out that someone who is already seen as somewhat appealing will be able to increase this by being funny. This means that people will also actively use this as a strategy to seem desirable to a potential partner.
People often claim ‘opposites attract’, however humans are not magnets. It actually seems like similarities attract, people are more likely to look for mates that share the same traits (Botwin, Buss, Shackelford, 1997).
Research has suggested that preferences for personality traits are influenced by culture, whereas physical attractiveness seems to be more universal. The differences between men and women were that men seemed to place more emphasis on physical attractiveness, while women looked for kindness, or humor. Though both genders found the aforementioned traits to be of importance, with intelligence being the highest ranked trait overall (Lippa, 2007).

Botwin, M. D., Buss, D. M., & Shackelford, T. K. (1997). Personality and mate preferences: Five factors in mate selection and marital satisfaction. Journal of personality, 65(1), 107-136.
Cunningham, M. R. (1986). Measuring the physical in physical attractiveness: Quasi-experiments on the sociobiology of female facial beauty. Journal of personality and social psychology, 50(5), 925.
Gangestad, S. W., & Thornhill, R. (2003). Facial masculinity and fluctuating asymmetry. Evolution and Human Behavior, 24(4), 231-241.
Grammer, K., & Thornhill, R. (1994). Human (Homo sapiens) facial attractiveness and sexual selection: the role of symmetry and averageness. Journal of comparative psychology, 108(3), 233.
Li, N. P., Griskevicius, V., Durante, K. M., Jonason, P. K., Pasisz, D. J., & Aumer, K. (2009). An evolutionary perspective on humor: sexual selection or interest indication?. Personality and Social Psychology Bulletin.
Lippa, R. A. (2007). The preferred traits of mates in a cross-national study of heterosexual and homosexual men and women: An examination of biological and cultural influences. Archives of sexual behavior, 36(2), 193-208.
Scheib, J. E., Gangestad, S. W., & Thornhill, R. (1999). Facial attractiveness, symmetry and cues of good genes. Proceedings of the Royal Society of London B: Biological Sciences, 266(1431), 1913-1917.
Singh, D. (1993). Adaptive significance of female physical attractiveness: role of waist-to-hip ratio. Journal of personality and social psychology, 65(2), 293.