Human Fertility and Fitness Optimization

Census and other sur\ej data from across the norld releal maJor differences m fertdlt! rates hetueen the more economIcall> debeloped and the less economIcall\ developed socletles The former are slgmficantly more likely than the latter to feature famlhes of tHo children or fewer hlultlple regression analysis shoHs that, among larlous mdlcaters of ‘Umodernlzatlon.” three (female level of education. female gainful emplo!ment. and proportion of phjslclans m the population) account for 71Cr of the barlatlon m farnil) size. all three larlables hale strong13 srgmficant. direct. and negatlre effects on fertdlt> The paper hvpotheslzes about the possible evolution of a reproductwe pqcholog> toward the two-child farnIl and seehs to explain hIghIS depressed rates of reproduction bl reference to both ultimate and proximate factors In some hIghI\ deleloped countries, zero-child and one-child rates of fertdlt\ represent together up to 40°C of all eter-married women. The findmgs stress the Importance of qstematlc research toward estabhshmg the proximate factors that are most hkelj to facdltate or Impede fitness optlmlzatlon-the Importance. that IS. of surrounding the optlmlzatlon prrnclple with the logic and ancdlarj propositions that will gwe It a greater and more dlrectl\e reach