9.1.1 Sexual Selection

Evolutionary Explanations for Partner Preferences

• Bodily Features and Behaviours: This concept suggests that physical traits and behaviours that are valued by the opposite sex increase an individual's chances of successful mating. Over time, these desirable attributes become more common in the species due to greater reproductive success.

• Genetic Quality: The genetic quality of a mate significantly impacts the genetic makeup of offspring. Mating with a low-quality partner is more likely to result in unattractive or unhealthy offspring, while mating with a high-quality, healthy partner increases the chances of producing strong, attractive offspring, thereby enhancing the likelihood of passing on one's genes.

  

• Female Mate Preferences: Females typically prioritise quality over quantity in mate selection. They are often attracted to males who can provide resources, physical protection, good parenting potential, and who minimise risks to themselves and their offspring.

• Male Mate Preferences: Males are generally attracted to females who display signs of fertility, which indicates their reproductive value. This is because males have a greater quantity of sperm and remain fertile throughout their lives, allowing them to maximise their reproductive success.

Intrasexual Selection

Intrasexual selection, often referred to as "mate competition," is the strategy typically employed by males. It involves competition between males for access to females.

Males that are successful in these competitions are more likely to mate and pass on their genes. Over time, the traits that lead to success in these competitions become more common in the population, contributing to sexual dimorphism (the physical differences between males and females).

Intersexual Selection

Intersexual selection, or "mate choice," is the strategy typically employed by females. It occurs when individuals of one sex (usually females) select their mates from a pool of available partners.

Females, who have a limited reproductive lifespan, are more selective in their mate choices to ensure the best possible survival of their offspring. Males, on the other hand, are attracted to young, fertile females as they can reproduce more frequently and with less investment.

• Impact on Competition: The preferences of one sex drive the traits that become competitive factors in the opposite sex.

Evaluation

Support for Intersexual Selection

Clark and Hatfield Study:

• Point: There is empirical support for intersexual selection from research conducted by Clark and Hatfield.

• Evidence: In their study, male and female psychology students approached other students on campus with a proposition to sleep with them. None of the females agreed, while 75% of the males did.

• Conclusion: This supports the evolutionary theory, as it demonstrates that females are more selective than males in choosing sexual partners, aligning with the idea that females invest more in reproduction and thus are choosier. Waynforth and Dunbar's Research:

• Point: Further support for intersexual selection comes from Waynforth and Dunbar's study of Lonely Hearts advertisements.

• Evidence: Their analysis of advertisements in American newspapers showed that women often emphasised physical attractiveness, while men highlighted their resources.

• Conclusion: This finding supports the evolutionary approach, showing that the preferences of one sex influence the traits the other sex competes over.

Support for Evolutionary Explanations

• Singh's Study on Waist-Hip Ratio (WHR):
  • Point: Evidence from Singh's research supports evolutionary explanations of mate preferences.
  • Evidence: Singh found that men across various cultures preferred a waist-hip ratio of 0.7 in females, which produces an hourglass shape indicative of fertility.
  • Conclusion: This supports the evolutionary explanation that men, who remain fertile throughout life, aim to maximise reproductive success by preferring fertile females.

Critiques of Evolutionary Explanations

Buller's Critique:

• Point: Buller argues that the evidence for a universal female preference for high-status men is weak.
• Evidence: He suggests that many studies on female mate preferences are conducted on undergraduate students, who expect to achieve high status themselves. Their preference for high-status men may reflect similar educational and social aspirations rather than an evolutionary preference.
• Conclusion: This challenges the evolutionary explanation, suggesting that preferences may be shaped by social and educational factors rather than purely by evolutionary pressures.

Limitations Regarding Non-Heterosexual Relationships:

• Point: A criticism of the evolutionary approach is its inability to explain the partner preferences of gay men and lesbian women.
• Evidence: Since homosexual relationships do not have reproduction as a primary goal, the evolutionary explanation of mate selection does not apply.
• Conclusion: This limitation suggests that the evolutionary theory is constrained to explaining partner preferences in heterosexual relationships and does not account for the diversity of human sexual relationships.