User:Wikieditor1017/sandbox

I plan on reading the sources that are in my sections (7) and (8) to gain an understanding of the writing done by previous editors. If anything is misrepresented I will flag the text and draft edits of my own to replace them. I also plan on doing a literature search to find any recent findings in the field that could be added to the sections to create a more complete dialogue.

Parasite Stress on Mate Choice
The parasite-stress theory, otherwise known as pathogen stress, states that parasites or diseases, stress the development of organisms, leading to a change in the appearance of their sexually attractive traits. In societies with a high prevalence of parasites or pathogens greater evolutionary advantage is derived from selecting for physical attractiveness/good looks of their potential mates, by the members of that society, compared to members of societies with a lower prevalence of parasites or diseases who put less emphasis on physical attractiveness. It indicates that physical attractiveness serves as a method by which humans can determine resistance to parasites, as it's believed that parasites and diseases would lower the ability to portray attractive traits of those who are suffering or have suffered from a disease, and would also limit the number of high-quality pathogen-resistant mates.

Hamilton-Zuk Hypothesis
The Hamilton-Zuk hypothesis (see Indicator traits) has greatly influenced research regarding human mate choice. The initial research showed that, within one species (brightly colored birds), there was greater sexual selection for males that had brighter plumage (feathers). In addition, Hamilton and Zuk showed that, between multiple species, there is greater selection for physical attributes in species under greater parasitic stress. In cultures where parasitic infection is especially high, members of that society use cues available to them to determine the physical health status of the potential mate. Regardless of the wealth or ideology, the females in areas of a society that are more at risk or have higher rates of parasites and diseases will rate masculinity as a higher priority.

Hamilton-Zuk Hypothesis in Humans

 * Scarification: In pre-industrial societies, body markings such as tattoos or scarifications are predicted to have been a way in which individuals could attract potential mates, by indicating the reproductive quality of a person. Meaning, scars on the body could be viewed by prospective mates as evidence that a person has overcome parasites and is thus more attractive to potential mates.. Research investigating this hypothesis (Singh and Bronstad 1997), found that in instances of increase pathogen prevalence, the only anatomical area with evidence of scarification in females was found on the stomach, with no evidence found for male scarification.


 * Masculinity: In societies where there are high levels of parasites or diseases, the females of that society, as the overall health of its members decreases, increasingly start to place more emphasis on masculinity in their mate preference. In particular, women look for increasing signs of masculinity in areas such as the voice, face and body shape of males. The face, in particular, may hold several cues for parasitic resistance and has been the subject of most attractiveness research.
 * Polygamy: Tropical areas were originally associated with polygynous societies and this was a result of the surrounding environment being both ecologically richer and homogenous. However, whilst tropical areas were associated with Polygamy, pathogen stress, is regarded as a better indicator of polygamy and has been positively correlated with it. Furthermore, over the course of human evolution, areas which had high levels of parasite-stress may have shifted the polygamy threshold and increased the presence of certain types of polygamy in a society.

Criticisms
Gangested and Buss (2009) say that research indicates that parasite stress may have only influenced mate choice through females searching for "good genes" which show parasite resistance, in areas which have high prevalence of parasites. John Cartwright also points out that females may be simply avoiding the transmission of parasites to themselves rather than it being them choosing males with good genes and that females look for more than just parasite-resistant genes.

MHC-Correlated Mate Choice
Major Histocompatibility Complex (MHC) or in humans, Human Leukocyte Antigen (HLA), produces proteins that are essential for immune system functioning. The genes of the MHC complex have extremely high variability, assumed to be a result of frequency-dependent parasite-driven selection and mate choice. This is believed to be so it promotes heterozygosity improving the chances of survival for the offspring.

Odour preferences
In experiments using rats, MHC-associated mate choice indicated that odor cues played a role. In humans, there is conflicting evidence about whether men and women will rate the opposite genders odor as more pleasant, if the potential mate has MHC-dissimilar antigens to them. However, women on contraceptive pills rate the odour of MHC-similar men as being more pleasant, it is unknown why women on contraceptive pills rate smell in this way. It was found that when processing MHC-similar smells were processed faster. Contrary to these findings, other studies have found that there is no correlation between attraction and odor by testing males' odor preferences on women's odors. The study concludes that there is no correlation in attraction between men and women of dissimilar HLA proteins. Research completed on a Southern Brazilian student population resulted in similar findings that found significant differences in the attraction ratings of giving to male sweat and MHC-difference.

Facial preferences
Human facial preferences have been shown to correlate with both MHC-similarity and MHC-heterozygosity. Research into MHC-similarity with regards to facial attractiveness is limited but research so far suggests that women, when thinking of long-term relationships, will choose males who are MHC-similar. While facial asymmetry hasn't been correlated with MHC-heterozygosity, the perceived healthiness of skin appears to be. It appears to be that only MHC-heterozygosity and no other genetic markers are correlated with facial attractiveness in males and it has been shown that so far that there is no correlation that has been found in females. Slightly different from facial attractiveness, facial masculinity is not shown to correlate with MHC heterogeneity (a common measure of immunocompetence).

Criticisms
A review article published in June 2018 concluded that there is no correlation between between HLA and mate choice. . In addition too assesing previous studies on HLA-Mate choice analysis to identify errors in their research methods(such as small population sizes), the study collects a larger set of data and re-runs the analysis of the previous studies. By using the larger data set to conduct analysis on 30 couples of european decent, they generate findings contrary to previous studies that identified significant divergence in the mate choice with accordance to HLA genotyping. Additional studies have been conducted simultaneously on African and European populations that only show correlation of MHC divergence in European but not African populations.