1. Introduction
The social environment shapes human life courses, and can generate strong associations between sociality, health, and longevity. For example, higher social status predicts longer lifespan (Adler et al., 1993; Chetty et al., 2016; Hajat et al., 2011; Lantz et al., 2010; Sapolsky, 2004; Wilkinson and Marmot, 2003), greater social support predicts healthier aging (Antonucci et al., 2019; Béland et al., 2005; Holt-Lunstad et al., 2010), and early life social adversity predicts higher mortality risk (Anda et al., 2006; Ferraro et al., 2016; Hughes et al., 2017). However, disentangling the effects of the social environment on human life courses remains challenging due to multiple uncontrolled (e.g., incongruencies in self-reported health; non-random attrition) and unknown confounding factors (e.g., biased survey information). Comparative approaches can both provide evidence concerning the evolutionary origins of the social determinants of human health and aging, and provide a model for the intricate interactions and potential feedback loops between sociality and aging (Carey and Judge, 2001; Lucas and Keller, 2020). This review argues that studies on the comparative biodemography of aging can advance our understanding of the link between individual sociality, population-level demographic outcomes, and the evolution of aging in humans. For this, we define senescence as a decline in function with age and differentiate it from health statuses which we define as deviations from such expected mean decline. We introduce conceptual frameworks for the evolutionary demography of aging within social contexts, discuss why current challenges in human health and aging studies call for comparative approaches, and describe a unifying methodological framework for the biodemography of aging that links current research in the social determinants of health to evolutionary demography approaches to the fundamental rules of life history evolution.