Explaining Below-Replacement Fertility and Increasing Childlessness in Wealthy Countries: Legacy Drive and the “Transmission Competition” Hypothesis

We propose a novel evolutionary perspective for explaining why, in most wealthy countries, female fertility has recently dropped below replacement level, with an increasing incidence of childlessness. Our hypothesis is based on the proposition that throughout human evolution, behaviors that promoted gene transmission (offspring production), and hence fitness, have involved not just those associated with a strong “sex drive,” but also those associated with a strong “legacy drive”—the desire to “leave something of oneself for the future. Because of this intrinsic legacy drive, we argue, humans (and males, in particular) have been inherently vulnerable for “side-tracking” into other activities that promote “meme transmission” — i.e., activities perceived as providing a lasting legacy of “self through investment in career development, accumulation of wealth and status, and several other activities that have potential to impact on the thoughts and actions of others in both current and future generations. Humans engage in meme transmission, therefore, at the potential expense of time, energy, and resources for investing in gene transmission. Based on evolutionary arguments, we discuss why realized competition between gene transmission and meme transmission has emerged significantly only in recent human history, why meme transmission is presently winning out in wealthy countries — thus accounting for below-replacement fertility and increasing childlessness — and why natural selection can be expected in the near future to generate a significant shift in the fertility-promoting behaviors of humans