Direct Benefits and Mate Choice

This entry was written by Emily Bender as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2

Introduction

Mate choice is the deliberate selection of a mate, because they provide certain benefits and can occur in both males and females. There are two main models of benefits one can obtain from a mate, direct and indirect, however direct benefits will only be discussed. Direct benefits are benefits that are immediately available such as resources. Indirect benefits are things like good genes that are passed on to offspring. The evolution of mate choice will be discussed as well as how benefits influence mate choice, and the consequences of being too selective of direct benefits offered by potential mates.

Main Text

Evolution of Mate Choice

Mate choice is an important part of sexual selection and helps drive it. This is because the individuals that mate successfully, will pass their genes on to the next generation. This leads to whatever traits that made them successful at getting mates becoming more common because they were selected for by the opposite sex (Kokko et al., 2003). This causes the continuation of those traits over time, eventually shaping the evolution of a species. Mate choice preference, which is preferences for certain qualities in mates, evolved because indiscriminate mating especially for females can have a negative consequence on fitness (Kokko et al., 2003). This negative consequence arises because mates may not invest in offspring or may not have enough resources to ensure their offspring’s survival to maturity (Kokko et al., 2003). This shows how mate choice evolved and how mate preferences developed as a result to maximise fitness and to ensure offspring’s survival.

How benefits influence mate choice

The availability of direct benefits has a huge influence on mate choice. This is shown by studies such as Buss (1990) which found that in 37 countries females placed the ability of a male to gain money above everything including looks (Buss et al., 1990). Whether females choose mates on account of indirect or direct benefits depends on what type of relationship they are seeking. For short term relationships females will favour potential mates that can give them direct benefits such as immediate access to lots of resources. This is because the relationship will likely not last and this allows them to get the most benefits from the relationship (Buss et al., 1990). Aside from the direct benefits of choosing mates with additional resources, there are also direct benefits from choosing mates that are healthy. The direct benefit of choosing mates that are healthy is that which is being in good condition and being minimally effected by pathogens is that one will avoid becoming ill (Tybur and Gangestad, 2011). Another direct benefit relates to the care of offspring, males will choose female mates, that are in good health because disease would impact the level of care given to future offspring (Tybur and Gangestad, 2011). However, there are risks associated with females choosing the fittest male to mate with, and that is risk of catching sexually transmitted diseases. This is because the fittest male if not in a relationship would have had more opportunities to catch sexual diseases, which could be passed on the future offspring (Tybur and Gangestad, 2011). This would lead to females not necessarily choosing the healthiest male, but perhaps the one that would provide the most direct benefits to offset the risk of getting sexually transmitted diseases (Tybur and Gangestad, 2011). This highlight how direct benefits help shape mate choice and mate preference in humans as well as the type of direct benefits mates look for.

Consequences of being too selective

There are a variety of direct benefits that potential mates may look for such as territory, investment in offspring and resources such as food and wealth, however there are costs to being too selective in mate choice. This is because individuals who are too selective, will miss mating opportunities (Courtiol et al., 2016). These missed mating opportunities, may then cause them to fail to reproduce, leading them to fail to pass their genes on to the next generation. Another consequence of being choosy is that for males it limits fitness maximisation because they have less opportunity to have more offspring (Pawłowski and Dunbar, 1999). This is in contrast to younger men which could start several families in their lifetime, capitalising on their fitness. Also, males who reject mates because they are too choosy then waste more time finding a suitable mate than females due to a male based operational sex ratio (Johnstone et al., 1996). This male based operational sex ratio occurs because males have the option for less parental investment, and because they may not been investing have more opportunity for mating, leading to a skewed sex ratio (Johnstone et al., 1996). Additionally, for women, who wait to long for a partner also face reduced fecundity and fertility, reducing the amount of offspring they can have. The risk of reduced fecundity is in many cases outweighed by the potential benefits of an economically well of mate, although. However, in in hunter gather societies, younger women normally choose mate with older men, because they provide more direct benefits and also because risk of mortality is reduced because it is typically the younger men with less resources that die (Pawłowski and Dunbar, 1999)..This shows the potential consequences of being too selective when it comes to mate choice, particularly for men.

Conclusion

Direct benefits have a large impact on mate choice and the relationship between the two can be complex. This is shown by the reasoning behind why mate choice evolved, as a way to maximise fitness and ensure that offspring survive. The type of direct benefits mates select for was also examined, as well as why they would select those benefits, for example individuals would choose healthy mates because it means they have less chance of becoming ill. The cost of being too selective was also examined and how that may decrease fitness.

Literature Cited

Buss, D.M., Abbott, M., Angleitner, A., Asherian, A., Biaggio, A., Blanco-Villasenor, A., Bruchon-Schweitzer, M., Ch’U, H.-Y., Czapinski, J., Deraad, B., et al. (1990). International Preferences in Selecting Mates: A Study of 37 Cultures. Journal of Cross-Cultural Psychology 21, 5–47.

Courtiol, A., Etienne, L., Feron, R., Godelle, B., and Rousset, F. (2016). The Evolution of Mutual Mate Choice under Direct Benefits. The American Naturalist 188, 521–538.

Johnstone, R.A., Reynolds, J.D., and Deutsch, J.C. (1996). MUTUAL MATE CHOICE AND SEX DIFFERENCES IN CHOOSINESS. Evolution 50, 1382–1391.

Kokko, H., Brooks, R., Jennions, M.D., and Morley, J. (2003). The evolution of mate choice and mating biases. Proc. Biol. Sci. 270, 653–664.

Pawłowski, B., and Dunbar, R.I. (1999). Impact of market value on human mate choice decisions. Proc. Biol. Sci. 266, 281–285.

Tybur, J.M., and Gangestad, S.W. (2011). Mate preferences and infectious disease: theoretical considerations and evidence in humans. Phil. Trans. R. Soc. B 366, 3375–3388.

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