Evolutionary demography of age at last birth: integrating approaches from human behavioural ecology and cultural evolution

Abstract

Cultural evolutionary theory and human behavioural ecology offer different, but compatible approaches to understanding human demographic behaviour. For much of their 30 history, these approaches have been deployed in parallel, with few explicit attempts to integrate them empirically. In this paper, we test hypotheses drawn from both approaches to explore how reproductive behaviour responds to cultural changes among Mosuo agriculturalists of China. Specifically, we focus on how age at last birth (ALB) varies in association with temporal shifts in fertility policies, spatial variation and kinship ecologies. We interpret temporal declines in ALB as plausibly consistent with demographic front-loading of reproduction in light of fertility constraints and later ages at last birth in matrilineal populations relative to patrilineal ones as consistent with greater household cooperation for reproductive purposes in the former. We find little evidence suggesting specific transmission pathways for the spread of norms regulating ALB, but emphasize that the rapid pace of change strongly suggests that learning processes were involved in the general decline in ALB over time. The different predictions of models we employ belie their considerable overlap and the potential for a synthetic approach to generate more refined tests of evolutionary hypotheses of demographic behaviour.This article is part of the theme issue ‘Bridging cultural gaps: interdisciplinary studies in human cultural evolution’.

Cultural group selection and human cooperation: a conceptual and empirical review

“…Lamba and Mace 2011). Recent empirical work in humans, both at the macro-scale (Botero et al 2014) and at the micro-scale (Colleran 2016;Mattison et al 2018), is beginning to bridge this gap by integrating how adaptive behaviour can arise based on the interplay of ecology, social learning strategies, individual decision-making and wider historical normative and institutional factors.…”

Biological Anthropology in 2018: Grounded in Theory, Questioning Contexts, Embracing Innovation

“…Mattison et al. () examined how ultimate and proximate mechanisms—in the form of adaptive decision making and transmission of social information—have combined to influence age at last birth among the Mosuo of China. Hypotheses derived from human behavioral ecology predict that relatively early reproductive stopping may be adaptive if it maximizes parental resources, allocare, or parental fitness given current demographic trends.…”

Bridging cultural gaps: interdisciplinary studies in human cultural evolution

“…They suggest that this stems from differences in both the underlying assumptions and the typical focus of the questions asked. Mattison et al [13] aim to reconcile these two fields, making their case with analysis of the cultural underpinnings of the age of women at last birth in the Mosuo population in China.…”

“…The aim of this issue is to advance interdisciplinary discussion of the roles that culture plays in shaping the course of human evolution, exploring the mechanisms of cultural evolution from their cognitive underpinnings in individuals, through the behavioural ecology of learning from others, to the dynamics of transmission at the level of individuals and populations. The articles in this issue bring insights from disparate disciplines to bear on major questions in cultural evolution [1-11] and suggest broad-scale ways in which the study of cultural evolution can be synthesized with other disciplines [12][13][14].…”

“…The aim of this issue is to advance interdisciplinary discussion of the roles that culture plays in shaping the course of human evolution, exploring the mechanisms of cultural evolution from their cognitive underpinnings in individuals, through the behavioural ecology of learning from others, to the dynamics of transmission at the level of individuals and populations. The articles in this issue bring insights from disparate disciplines to bear on major questions in cultural evolution [1-11] and suggest broad-scale ways in which the study of cultural evolution can be synthesized with other disciplines [12][13][14].In the introduction to this issue [15], we outline how integrative studies are poised to move the field of cultural evolution forward; we demonstrate the utility of this approach by reviewing a number of interdisciplinary studies in cultural evolution and related fields that encompass behavioural ecology, population dynamics, cognition and genetics. Next, in the special issue's first article, Truskanov & Prat [1] bring insights from the behavioural ecology of social learning in non-human animals to bear on the underlying mechanisms of cultural transmission.…”