Briefly, we outline two sets of theoretical frameworks that are largely shared across the social and biological sciences yet are often, and unknowingly, applied separately. Trivers RL. High birth sex ratios, some claim, may be caused in part by social factors.
Thus whether or not a particular indicator, such as male marital status, is a useful measure of MM predictions depends on the population under study. Sons are preferred because i they have a higher wage-earning capacity, especially in agrarian economies 24 ; ii they continue the family line; and iii they are generally recipients of inheritance 25
Another challenge, among humans in particular, is to refine the definition of the ASR for the population under study [ 32 ]. Accordingly, here we examine reproductive outcomes across individuals in response to the ASR experienced both in one's youth and adulthood simultaneously.
First, access to prenatal sex determination results in an increase in the proportion of wanted births, leading to less discrimination against girl children and lower female mortality. News, views and top stories in your inbox. The rarer sex has more bargaining power and can leverage their scarcity to realize their preferred mating strategy, while the more common sex must cater to the preferences of the rarer sex in order to acquire a mate.
External link. The Lancet Infectious Diseases. A combination of changing migration patterns and US immigration restrictions acted to shift the male-female balance in many ethnic groups in the early 20th Century. Utilising information on sex-specific mortality during early childhood, it can be shown that the sex ratio of for ages in implies a sex ratio at birth of during the seven-year period preceding the census, that is, roughly during the period The third model in Table 2 presents the results for whether the respondent tests positive for a sexually-transmitted infection STI.
In an attempt to clarify the role of the adult sex ratio ASR on behaviour, here we evaluate both competing and complimentary expectations derived from theory across the social and biological sciences. A self-consistent approach to paternity and parental effort.
Uggla C, Mace R. The UPDB is a unique research resource that enhances the value and furthers the advancement of research in studies linking early life circumstances to health and behavioural outcomes later in life.