Evolution, diversification and function of the maternal–infant dyad in mammalian feeding

Abstract

The evolution of the mother/infant dyad providing a source of nutrition for infants is essential for the origin and subsequent diversification of mammals. Despite the importance of this dyad, research on maternal and infant function is often treated independently. Our goal is to synthesize the work on maternal and infant function, discuss our own studies of suckling, and compare the origins of lactation and suckling with their ensuing diversification. Our central premise is that while extensive work has demonstrated variation across mammals in the maternal aspect of this system, very little has been done to address how this relates to infant function. We start with a discussion of the fundamental anatomy and physiology of both mother and infant. We next discuss the origin of mammary glands and milk, and infant suckling, which is distinct from their subsequent diversification. We then discuss the diversification of maternal and infant function, highlighting the evolutionary diversity present in maternal function (both anatomically and physiologically), before arguing that the diversity of infant function is unexplored, and needs to be better studied in the future. We end by discussing some of the holes in our understanding, and suggestions for future work that can address these lacunae. This article is part of the theme issue ‘Food processing and nutritional assimilation in animals’.

Introduction: food processing and nutritional assimilation in animals

“…Life-history changes in oral processing have focused on the mammalian transition from suckling to chewing. During this transition in mammals, oral processing undergoes a monumental shift from a fluid substrate to solid or semisolid foods, resulting in changes in muscle activation patterns, jaw loading, tongue movements and swallowing [ 71 , 72 , 85 , 86 ]. However, animals other than mammals also undergo developmental transitions necessitating changes in oral processing, and there is a distinct lack of studies exploring these transitions.…”

“…Most of the studies in this issue examine food processing and nutritional assimilation across short time-scales. While short-term studies provide valuable insights, there is a need for research across longer time-scales to understand how these systems respond to ageing, and in turn, how food processing and nutritional assimilation impact overall health, growth and disease prevention over extended periods (reviewed in [ 71 , 72 , 86 ]).…”