Relationships: Sexual Selection And Human Reproductive Behaviour Flashcards
What is sexual selection?
It provides an evolutionary explanation for reproductive behaviours seen in modern. Humans as it suggests behaviours that increase reproductive success are passed on through genes, leading them to become common in modern humans.
- One type of sexual selection that influences human reproductive behaviour is inter-sexual selection. This occurs when one gender makes mate choices based on a
specific characteristic of the other gender (e.g., physical height).
- Evolutionary researchers have argued that inter-sexual selection (mate choice) is most relevant for
female reproductive behaviour. This results in an important reproductive behaviour: the relatively high level of female “choosiness” in mate selection, i.e., women will be more discerning than men in who they select as a partner.
- The cause of this difference in choosiness is that females have higher levels of parental investment than males. One cause of this high investment is that women can have fewer children than men (for various reasons, like the menopause and the menstrual cycle, women have a more restricted fertility window than men). Another cause is the greater energy investment in each child (e.g., pregnancy and breastfeeding are demanding).
Consequently, female “choosiness” evolved through sexual selection as females have a lot to lose if they select a
sub-standard partner.
emale choosiness has implications for the type of characteristics sought in a potential mate. For example:
- Preference for characteristics like physical strength/height, intelligence, access to resources, loyalty and characteristics associated with nurturing (along with many others) may have been sexually selected through intersexual selection as women and their children might receive better protection from such partners, meaning they would be more likely to reproduce and raise children that survive long enough to pass n their genes
- Intersexual selection may be more important for females, but it still matters for males. This explains the common
preference for a characteristics in a female partner (e.g., appearing old enough to have passed through adolescence but youthful enough not to have reached the menopause youth indicate reproductive fitness (the woman hasn’t entered the menopause) - According to the “sexy son’s hypothesis”, preference for partners with desirable characteristics ) may have been sexually selected because such characteristics can be inherited. This matters most if this child is a son, as he will have to compete against other men to be selected by “choosy” women, allowing him to pass on his (and his parents’) genes. Therefore, it pays for a woman to be choosy and select a “sexy” partner who will pass on his “sexy” genes, creating a “sexy” son who will…and so on.
What is a type of sexual selection?
- Intrasexual selection. This occurs where members of the same sex compete with one other for members of the opposite
sex - Evolutionary researchers have argued that intra-sexual selection (mate competition) is most important for explaining
the evolution of male reproductive behaviours.
reproductively fit females (meaning able to have children) are rarer than reproductive fit males. This availability is
further limited by female choosiness. This scarcity of female partners encourages males to compete for access, and
this leads to the sexual selection of various reproductive behaviours. For example:
- Male aggression – men are much more aggressive than women. It’s possible this aggression evolved through sexual selection as the more aggressive males were able to dominate less aggressive males, and so secure access to reproductively fit women.
- A lack of male choosiness – Due to parental investment, reproductively fit (and willing) females are more scarce, leading males to compete for available partners. In this competitive environment, males who were less choosy would reproduce more than the choosy males, meaning a less choosy reproductive strategy
would be passed on and inherited by modern males. - Mate guarding - Research has found that mate guarding (jealously guarding a partner from the interests of
potential rivals) is a reproductive behaviour especially common in men. This reproductive behaviour can be
explained by male-male competition for women. Because women can have fewer children, they are in high
demand, leading to competition between males for the opportunity to reproduce with them. From an evolutionary perspective, mate guarding is a potentially effective strategy for helping a male outcompete other males, and therefore successfully pass on his genes. Genes that lead to mate guarding may therefore have been sexually selected in males.
Why may Explanations of human reproductive behaviour in terms of sexual selection may be socially sensitive?
Explanations of human reproductive behaviour in terms of sexual selection are easily misunderstood , and this has the potential for harmful social consequences for men and women. For example, presenting reproductive behaviours like female choosiness (and a lack of male choosiness) as
sexually selected, could be interpreted as implying they are necessarily universal. This would not only be a
misinterpretation, as individual differences fuelled by genetic variation are a necessary feature of evolution, but also a socially sensitive mistake as it might lead to stigmatization against individuals who deviate from these behavioural
norms (e.g., women who are not choosy/men who are or atypical partner preferences). Another potential issue is that claiming a reproductive behaviour has been sexually selected might suggest it is “natural” and, by association, morally correct. This may be problematic, as it may serve to justify socially harmful behaviours, like aggression. Moreover, it reflects a misunderstanding of evolution, as explaining a behaviour through sexual selection only
implies that it once had reproductive benefits. This implies nothing for its moral acceptability. Furthermore, it may
well be that behaviours that were reproductively beneficial thousands of years ago may be counterproductive in
today’s society (e.g., excessive male aggression may be disadvantageous today). A final issue concerns the extent to which research into the link between sexual selection and human reproductive behaviour can be fruitfully applied to homosexual relationships. The issue is that sexual selection necessarily concerns reproduction, and since this is impossible in a homosexual relationship, it’s possible that none of the research findings on this topic can be applied
to homosexual relationships. Despite all these issues, it could be argued that research into the link between human reproductive behaviour and sexual selection is beneficial as it can help us understand the biological basis for such
behaviours, society may be better informed and better equipped to address socially undesirable behaviours, like
male aggression or mate guarding.
Research into the relationship between sexual selection and human reproductive behaviour may be
methodologically flawed.
According to Buller (2005), the majority of studies on female mate preference have used female undergraduates
as participants. Such women expect to achieve high educational status and so have expectations of high-income levels. The fact that these women express a preference for high-status men might be explained by the evolution of female ‘choosiness’ in partner preference through thousands of years of sexual selection. However, it’s also possible that finding that undergraduate women seek partners of a high educational status may simply reflect their desire for a partner who is like them. This illustrates how research into the relationship between sexual selection and human reproductive behaviour may be undermined by a lack of representative samples.
How can Sexual selection help explain variations in female reproductive behaviour during the menstrual cycle?
For example, Penton-Voak (1999) found that for most of their cycle, women showed a preference for slightly
feminised male faces, but preferred more masculine faces whilst ovulating. This human reproductive behaviour can be explained by sexual selection. Given the women’s greater parental
investment, women are likely to favour a more feminine partner as feminine characteristics, such as being nurturing,
are valuable in a long-term partner. However, a more masculine face may be preferable when ovulating as this may
indicate ‘strong’ genes that a woman would hope to pass on to her offspring. However, this study’s finding on the
link between human reproductive behaviour and sexual selection may lack credibility due to its lack of ecological
validity. The task in this experiment is highly artificial and may therefore reveal little about the reality of female reproductive behaviours.
