Abstract
In the course of the last century industrialized countries have experienced significant changes in mortality rates. Since the sex ratio of a population may be considered a function of, among other factors, differential mortality in the two sexes, it is expected to correlate with changes in sex-specific mortality rates. In this paper secular changes in the sex ratio at birth and after the action of relevant components of early selection (stillbirth, mortality within the first month and within the first year of life) have been studied in the Italian and in the USA White populations. The results can be summarized as follows. (i) In the past, extra male-specific mortality appeared to reduce the relatively large values of the sex ratio observed at birth, and this held true in both populations. (ii) In more recent times, male-specific mortality has been decreasing in all age groups, and the sex ratios before and after the action of early selection now tend to identical values. Therefore, it can be envisaged that in the near future the sex ratio observed at birth will be maintained up to the reproductive age. If the reproductive value is stabilized by natural selection, as is likely, new relationships between sex ratio and selection may be expected to develop in a relatively short time.
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
