Suchergebnisse

Abstract
According to the Trivers–Willard hypothesis (TWH), when the mother's condition around conception influences the future reproductive success of male and female offspring differently, the adjustment of offspring sex ratio (SR) to maternal condition will increase the parents' fitness. The TWH has been tested in several taxa, including humans where socioeconomic status as an index of condition has been widely used. The results are inconsistent, possibly because the preconditions of the TWH are not always met. To investigate the preconditions and prediction of the TWH in the contemporary Hungarian population, we collected data by an online questionnaire on self-perceived childhood living standard, the number of children and the sex of the respondents' siblings. We found no sex-specific relationship between reproductive success and childhood living standards, thus the precondition of the TWH was not met. We found no relationship between socioeconomic status and offspring SR when data from the whole country was used, but there was a tendency in the predicted direction when we used data from Budapest and considered the SR of only those family members who were born under similar conditions. Similar approaches should be preferred in the future to avoid noise caused by changing status during the reproductive lifespan.

SummaryGuerrero (1975) has cited a wealth of direct data supporting the hypothesis that timing of insemination is related to the sex of the resulting zygote. It is argued here that if this hypothesis were correct, then parental coital rate would be associated with the sex of the resulting children. It is suggested here that empirical data support this inference and hence support the hypothesis.It is estimated that if Pmale (the probability that a zygote will be male) declines linearly across the fertile period, that decline is from about 0·57 to 0·45.