The fast-slow continuum is not the end-game of life history evolution, human or otherwise

Abstract

Life history human evolution places a strong emphasis on the fast-slow continuum and pace-of-life continuum. Papers in this area frequently make a call for more integrative research to explore the relationships between the fast-slow continuum (population-level variation in traits) and pace-of-life continuum (ditto at the individual level). Here, using high-resolution demographic models from natural populations of 41 modern human populations, and hundreds of non-human animal populations and plant populations, I show that the fast-slow continuum, while of interest to explore variation in human strategies, should not be the sole focus of attention. Using a phylogenetically corrected principal component analysis, I show that other axes of life history variation show great promise. Specifically, understanding of the mechanisms of inter-specific and intra-specific differences in senescence rates in reproduction and survival, and how species respond to stochastic variation, I argue, should become the focus of my interdisciplinary research. The proposed new axis of demographic buffering-lability emerges as an important one to explain over 20% of variation in human and non-human populations. I show that these axes help predict demographic resilience, and also correlates with human nation per capita GDP and population growth rates.