Süssmilch, a German army chaplain, produced an important book on vital statistics, the title of which translates as The divine order in the circumstances of the human sex, birth, death and reproduction.  Among other things, he showed the necessity of a healthy and industrious population for the survival of a nation. Süssmilch discovered that, in the long term, there is a constant sex ratio of 1,000 female births to 1,050 male births. His work was the most important until the time of Malthus. Digital facsimile of a printed facsimile of the first edition from the Hathi Trust at this link.