Lecture 2 Flashcards
What is polyandry?
The opposite of polygyny so it’s when one woman has many male partners.
Discuss monogamy and culture briefly
It is greatly affected by culture. For example, there are many cultures where polygyny is the norm and some argue that monogamy only exists because it’s enforced by the law.
Who does polygyny benefit the most?
Wealthy, successful men.
Why would women accept a polygynous guy and be a second wife?
Because trade-offs happen; decision making model. For example, as a man’s wealth rises, so does a women’s reproductive success to a certain point where the curve plateaus. Although reproductive success starts off higher for monogamous relationships, it comes to a point where a wealthy polygynous man provides the same reproductive success as a less wealthy monogamous man. This is the polygyny threshold model.
Why aren’t all cultures polygynous?
Polygyny is only favoured if there a large variety in the quality of males. For example if resources can be monopolised or if conditions emphasise the differences like diseases. A cross cultural study was done that showed greater polygyny when there was increased exposure to disease.
Who loses out from polygyny?
The majority of men who don’t have a lot of resources.
Discuss matrilineal vs partilineal inheritance and the interests of the parents
Patrilineal inheritance in when the father’s leave their wealth to their offspring. This is most advantageous in polygynous societies as the wealth can be used to attract females. However, the parents have conflicting interests; the males want to use all of their wealth buying wives but the mothers want the sons to inherit the wealth. This correlates with the Oedipus complex except in terms of mothers supporting the son’s polygyny and not the father’s. This also highlights how polygyny can promote a women’s fitness (via their sons).
Matrilineal inheritance is when the mother’s pass on their wealth. When a male inherits the wealth, they usually pass it on to their sister’s son because of paternity uncertainty so they don’t want to give their potentially unrelated offspring any wealth. Therefore, they must believe that their nephew (0.25) is more related to them than their offspring (less than 0.25 probability that the child is mine). However, if paternity certainty is so low in this society then you may not be fully related to your sister. Most societies have this inheritance when women are economically important (horicultural societies) as opposed to pastoral societies.
Discuss incest and marriage patterns
Reproduction between close relatives increases the chances of inbreeding; recessive conditions. Therefore, culturally laws enforce against this. It is argued that we have evolved not to be sexually attracted to siblings due to the close proximity growing up; this is the westermarck effect. This has been supported by Shepher’s study. They observed Kibbutz children who are raised among peers rather than siblings and found that none of them married members of the same peer group. Additionally, divorce higher when Sim Pua children where raised with their future spouse compared to being introduced to them after puberty. However, if incest avoidance is autonomic then why are laws needed to prevent it. It could be argued that they’re made to prevent families becoming too powerful (e.g. laws against close kin and distant kin) or to prevent adultery (e.g. laws on affinal kin; in-laws). This is supported as affinal incest laws have worse punishments in patrilocal societies (moving into the husband’s home) as there’s more opportunities for adultery. Therefore, there is support for incest laws being created to assert power; powerful people are allowed to be incest but lower class families aren’t.
Why does polyandry exist?
The traditional evolutionary explanation argues that it’s because of an impoverished environmental situation; e.g. men are unable to support their wives. Fraternal polyandry is most common (brothers sharing a wife), e.g. it’s common in Tibet as it is economically effective; each husband has a different job role. This can be explained by Hamilton’s rule; assuming that the younger brother will not get offspring otherwise. If they pair up then the mean offspring between them is 5.2. However, in monogamous circumstances it would be 3.1. Additionally, this means that the senior brother ends up worse off leading to a conflict of interest but it continues because the younger brother, the wife and their parents end up better off.
What is the main theme of the marriage and inheritance lecture?
The idea that there is a complex interaction between culture and biology. For example; cultural incest rules might affect inheritance more than inbreeding avoidance. Also, polyandry can be explained by adaptive conflicts of interest but also by non-adaptive economically-driven decisions.
Discuss monogamy and crime
In monogamous cultures there is less crime as there is less competition for resources.
What causes fraternal polyandrous marriages to break down?
If the younger brother gets economic opportunities, then they can pursue monogamous marriages, however, this could then have a large economic price.
Also, they can break down as the number of siblings increases because there is a negative correlation between birth order and number of offspring.
Discuss Josephson’s study
They did a study exploring relationships in Utah from the 19th century. They found that women who married polygynously had less children but more grandchildren than monogamous couples. Therefore, there is a trade-off between decreased fertility for better reproductive performance of their offspring. This shows that a female’s reproductive decisions can influence social structure and challenges traditional views of fitness.
Discuss Chapais’ study
Not only is matrilineal inheritance common among humans, it is also common among macaques suggesting a deep-rooted evolutionary drive behind it. Chapais found that macaques inherit their mother’s or sister’s rank within the society and these ranks are primarily inherited during aggressive interventions (the younger macaque and their older related macaque act aggressively together).
Discuss Lieberman’s study
They expanded on the Kibbitzum and Taiwanese studies and Westermarck’s hypothesis. They explained that incest avoidance develops differently for younger and older siblings. Younger siblings learn via childhood coresidence with the siblings. Older siblings learn via exposure to the mother caring for the newborn. This suggests that there are environmental/cultural influences involved (learning who siblings are) but also a genetic predisposition as they are not told outright that incest is bad at this age. They just avoid it once discovering who their nuclear family is, suggesting that avoidance is somewhat innate.
