The Adaptive Value of Love: Evolutionary Mechanisms Underlying Mate Selection

Introduction

In the mating game, men and women have a variety of conscious and unconscious strategies that they utilize to secure partners. These strategies were developed over millions of years of evolution, and we’re still programmed to use them today. This programing has developed in every living thing that reproduces sexually. The comparisons between species are an aspect that is vital to fully understand mate selection. One of these differences is the influence of the modern world on humans having sex.

Although science is far from having all the answers to why we behave in the ways we do, people have discovered some possible explanations.

The Mechanics of Human vs Animal Mate Selection

Sexual selection, according to Arianne Albert and Dolph Schluter in their article, “Selection and the origin of species”, is when a member of one sex mates with a member of the other sex due to various reasons. With reference to humans it is the form of natural selection that favors characteristics that assist in either attracting the selecting sex or help one in competing with others f the same sex. We attempt to clarify what some of the general factors underlying animal and in specific human mate selection are.

    Albert and Schluter both argue that the outcome of sexual selection can be seen in the behavioral displays as well as the genital shapes and sounds that “characterize male courtship and mating behavior.” Male peacocks must impress the peahens with impressive feather displays and the peahen is given the ultimate choice. Human selection is similar to mating behaviour amongst other animals in this respect because the onus of impressing the prospective mate falls on the man. Mammal females tend to be more selective of their mates as, in accordance with the differential parental investment theory, the woman has an initially higher investment in the offspring and therefore has more to lose from a genetically poor mate. Males can fertile at minimal cost as their direct input requires no more then their genes. Women however, invest the gestation period as well as the postnatal care and therefore they have to ensure that this investment has not been in vain. Women therefore tend to demand evidence of superior genetic capability before choosing to mate while men are relatively non-selective about their choice of mate. 

Click on the link below to further this information with a video:

http://videos.howstuffworks.com/animal-planet/28898-ms-adventure-primping-peacocks-video.htm

Hanna Kokko, Robert Brooks, Michael D. Jennions, and Josephine Morley, in their article, “The evolution of mate choice and mating biases” argue that there are two types of selection: direct and indirect. Direct selection (the one related more closely to successful evolutionary practices) is when the sexual selection is made to increase fitness. “A female’s mating biases are favored by direct selection if they increase he own lifetime reproductive output. Direct selection favors mating biases toward males that are more fertile, provide superior resources, offer more parental care or otherwise reduce the female’s current reproductive costs,” (3). Thus sexual selection in the direct sense is based on increased fitness overall.

Due to the structure of human society and the emphasis on monogamy, it is assumed that the man will directly contribute genes and indirectly contribute resources, financially and temporally, that will be needed to meet the needs of the offspring. Human mate selection  therefore follows along similar lines where a man’s genetic potential is valued by his physical attractiveness while his fitness potential is valued by his social standing, dominance within the social hierarchy or ambition.

Indirect selection however, is the selection of a mate based on characteristics that could possibly endanger the viability of the species. In the case of peacocks for instance, peahens tend to mate with the more attractive of the peacocks but the excess plumage however, makes these peacocks more vulnerable to predators. Indirect selection is therefore more about preference than about fitness, an aspect of evolutionary mate selection that is playing into evolutionary discourse today.

Kokko’s article says that “fitter males and the females who preferentially mate with them, will have offspring that inherit the genes for both fitness and the mating preference,” (3).Thus, the genes for both indirect and direct selection are passed to the offspring. Direct selection seems self-explanatory in terms of evolution: the fact that the female would choose a male who would increase overall fitness would fall right in line with natural selection and therefore evolution. However, indirect selection is a little more questionable. How do females evolve to choose males indirectly? How does natural selection allow for females to choose traits that might not be beneficial for survival?

One theory, Kokko’s article argues, is that a process called sensory drive pushes females to choose males indirectly (4). “It may provide the initial ‘nudge’ often required to initiate choice-display coevolution. If males are not advertising, females are unable to choose…” (4). Thus in order for reproduction to work, males must advertise their features and these features are picked up by the females whose sensory drive processes choose which males to mate with. this argument is gaining more relevance today with the debate on the impact of birth control and its impact on evolution and natural selection. 
Watch the Video below to further your understanding.

 

Mate Selection for Females and Males

         According to many scholars, male and female mate selection is concerned with exploiting the “reproductive potential and reproductive investment of members of the opposite sex” (Geary, 29). 

         Reproductive potential is the “individuals’ ability to invest in the growth, development, and later social and reproductive competencies and/or the potential genetic benefit a make would confer on offspring” and “reproductive investment is the expenditure of this potential on offspring” (Geary, 29).

        In addition to biological factors, mate selection is restricted by kin, the marriage system, societal expectations, and ecological conditions. These factors impact human females and males in different ways and, therefore, impact their mating preferences in unique, sex-specific ways. Women’s mate selection strategy is to select a mate who will conceive, raise and provide for a child with them. This strategy causes the cost of reproduction to be higher for women than for men and weight costs versus benefits when selecting potential long-term and short-term partners. In contrast, human males, like other males, compete for “access to preferred and oftentimes, multiple mates” in order to produce as many offspring as possible (Geary, 29). With this objective, males seek out more short-term relationships and are more hesitant about entering into long-term relationships and thus the are more careful when selecting  long-term partners. Although these biological drives greatly influence our mate selection they do not completely determine who are partners will be. Culture, societal expectations, sexual preference and other factors influence our actions on these unconscious drives.

       Visit this link below to watch a video on "The Science of Sex Appeal"

http://videos.howstuffworks.com/discovery/35981-science-of-sex-appeal-women-are-choosier-video.htm 

Sources:

Multimedia Resources:

http://www.pbs.org/wgbh/evolution/library/01/6/real/l_016_08.html

Sources.

Hanna Kokko, Robert brooks, Michael D. Jennions and Josephine Morley. “The
evolution of mate choice and mating biases.” http://rspb.royalsocietypublishing.org/
content/270/1515/653.full.pdf+html

Arianne Y.K. Albert and Dolph Schluter. “Selection and the origin of species.”
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Mark Ridley. Evolution. http://www.blackwellpublishing.com/ridley/a-z/
Peacocks_Tail.asp

Mate Selection - Evolutionary Factors. <http://family.jrank.org/pages/1147/Mate-Selection-Evolutionary-Factors.html>