female:male ratio in K-3 kids

[Sophie Wilson]

Jennifer S Kassie (jkassie at uoguelph.ca) wrote:
: Sophie Wilson (sophiewi at uoguelph.ca) wrote:
: : And I dimly remember from a biology class that as women 
: : age, they are more likely to produce female babies than male babies.  Is 
: : it possible that the average age of the MOTHERS might be a factor here?


: But doesn't the male (who carries both X and Y chromosomes) determine the 
: sex of the baby?  Females can ONLY contribute an X chromosme.  

Two things... isn't there now some discussion about whether certain eggs 
may be more receptive to X or Y sperm - so the woman's eggs may actually 
have 
some determining input?  (I read this in a newspaper... so I'll happily 
accept correction.)
AND - I understand that females are more hardy right from the start, i.e. 
even before birth.  So IF an older uterus is not a perfect environment, 
then perhaps female zygotes/fetuses will have a higher survival rate than 
their male counterparts.  Hence, older mothers may give birth to more 
girl-children than the average.  (Again, correction happily accepted...:))