Marriage is an evolutionary puzzle: It is unique to our species and found across human societies, yet also varies widely in form and function. Human marriage likely evolved from ancestral primate patterns of pair bonding and its universality in human societies suggests a deep evolutionary history. Indeed, some have argued that marriage is part of the evolution of a human-specific social structure linking relatives and nonrelatives together into uniquely large and complex social groups. Yet, the many cross-culturally variable aspects of marriage show how marriage systems are shaped by adaptive responses to local subsistence systems and environments through strategic decision-making relevant to reproduction, parental investment, and the acquisition and distribution of resources. Marriage is thus a species-typical adaptation with locally adaptive variation that has coevolved with systems of kinship, family, and inheritance – providing a profound example of the entanglement of human biological and cultural evolution. This chapter explores the evolutionary underpinnings of marriage and how patterns of marriage vary cross-culturally in response to local ecological conditions, focusing on the functions of marriage, when to marry, whom to marry, who makes marriage decisions, how many spouses one should have, where one should live after marriage, and how marriage is bound up in systems of resources, kinship, parental investment, and exchange.

Chapter 3 explores how and where individuals met their future marriage partners. From the eighteenth to the early twentieth century there was a gradual expansion in the spatial range in which the search for a marriage partner took place.The move into towns and cities broadened the spaces for courtship.This chapter also looks at the ages at which people married and the changes that came about in age of marriage over the period. It reveals that from the seventeenth through to the early twentieth century, financial and material considerations formed a central part of the negotiations for the majority of marriages. Marriage was used by families as a means to accumulate additional economic resources or to retain land within a particular family. The size of a dowry could vary, depending on class, family income, and the numbers of daughters requiring a marriage portion.The perception that the dowry and arranged marriages became more pervasive in post-Famine Ireland is, however, not supported by the evidence. Dowries, whatever shape they took, made marriages an explicit business deal.Assets and the rights brought with them, provided the expectation of a wife’s control of her own household, the support of a husband and the safety of a family unit in which all might prosper.