A Terminal Mesozoic Greenhouse

1979 Science  
McMillen (/) may be correct in "conservatively" estimating the primary ratio of human male to female conceptuses to be at least (Y,:100 =) 120: 100, but the argument she presents shows only the consistency of that range of ratio values with certain selected empirical data. Since the quantity of interest is y" the proportion of males at conception [or equivalently Y, = 100 y,/(lyl)], the analysis is much simplified by solving the equation of her reference 14 for y, [d defined below, the other
more » ... iables as in YI=Y2(l -f)l[d(y2l)f + II where f = proportional female zygote loss, "'reported" to be between 0.2 and 0.5; d = mf = excess male-over-female mortality ratio, "observed" to be between .04 and .18; Y2 = the proportion of live-borns that are male, the male secondary sex proportion, observed to be between .5115 and .5131 for the later (1950 to 1972) of two sets of data used in her analysis. With this equation for Yi, the cited ranges off, d, Y2, and the definition of Y1, we obtain Y1 values between 110 and 165; this range is quite close to the previous estimates, 110 to 170, that McMillen cites in her first paragraph. Thus she has not succeeded irq reducing the range of uncertainty regarding the primary sex ratio.
doi:10.1126/science.206.4425.1428-a pmid:17739302 fatcat:pc7ht4urrvf6dot74nxxzjp3um