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Variation in human secondary sex ratio after extraordinary natural, social and cultural events
Hubová, Hana ; Kaňková, Šárka (advisor) ; Dušek, Adam (referee)
The secondary sex ratio represents the proportion of male and female births and is usually slightly skewed towards male births. Changes in the secondary sex ratio may be induced by a variety of ultimate (evolutionary) or proximate (physiological) causes. These causes tend to be linked to external factors such as natural disasters, armed conflicts, terrorism and/or important cultural and sports events. Natural disasters cause major destruction of housing, infrastructure and loss of lives. Such events are likely to be followed by a decrease in the secondary sex ratio. Stress-induced selection in utero against males is one of the widely discussed causes related to this phenomenon. Armed conflicts and terrorism commonly have a negative impact on society as well, however, an increase in the secondary sex ratio was often observed in the post-war periods. Important cultural and sports events, along with holiday celebrations, have a mostly positive impact on the social climate. These events induce a sense of community and are likely to be followed by an increase in the secondary sex ratio 9 months later, which suggests higher coital rates during such events.
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BABY BOY OR BABY GIRL
Zákostelná, Lucie ; Hebák, Petr (advisor) ; Burdychová, Bohdana (referee)
The thesis is mainly focused on the analysis and evaluation of the effects influencing the sex ratio of live births. After studying of the foreign language literature, main factors influencing the sex ratio are defined. Data used in the thesis (births by the sex) are retrieved from The Human Mortality Database, database of United Nations Statistics Division and from particular statistical offices. Based on the results of the exploratory data analysis, countries with unreliable data (data skewed due to the manipulation or due to the not appropriate standard of the registration of born) are specified. Subsequently, the countries with abnormal values of the sex ratio at birth resulting from the cultural traditions or technological development are defined. For countries with not evident influence of the factors mentioned the analysis of the relations and dependencies between sex ratio at birth and variables chosen (groups of the geographical, socioeconomics and demographical impacts). On the basis of this analysis it has been proved that the sex ratio at birth depends primarily, but not exclusively, on the total fertility rate and life expectancy.
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