Romantic love is a phenomenon of immense interest to the general public as well as to scholars in several disciplines. It is known to be present in almost all human societies and has been studied from a number of perspectives. In this integrative review, we bring together what is known about romantic love using Tinbergen’s “four questions” framework originating from evolutionary biology. Under the first question, related to mechanisms, we show that it is caused by social, psychological mate choice, genetic, neural, and endocrine mechanisms. The mechanisms regulating psychopathology, cognitive biases, and animal models provide further insights into the mechanisms that regulate romantic love. Under the second question, related to development, we show that romantic love exists across the human lifespan in both sexes. We summarize what is known about its development and the internal and external factors that influence it. We consider cross-cultural perspectives and raise the issue of evolutionary mismatch. Under the third question, related to function, we discuss the fitness-relevant benefits and costs of romantic love with reference to mate choice, courtship, sex, and pair-bonding. We outline three possible selective pressures and contend that romantic love is a suite of adaptions and by-products. Under the fourth question, related to phylogeny, we summarize theories of romantic love’s evolutionary history and show that romantic love probably evolved in concert with pair-bonds in our recent ancestors. We describe the mammalian antecedents to romantic love and the contribution of genes and culture to the expression of modern romantic love. We advance four potential scenarios for the evolution of romantic love. We conclude by summarizing what Tinbergen’s four questions tell us, highlighting outstanding questions as avenues of potential future research, and suggesting a novel ethologically informed working definition to accommodate the multi-faceted understanding of romantic love advanced in this review.

For 25 years, the predominant evolutionary theory of romantic love has been Fisher’s theory of independent emotion systems. That theory suggests that sex drive, romantic attraction (romantic love), and attachment are associated with distinct neurobiological and endocrinological systems which evolved independently of each other. Psychological and neurobiological evidence, however, suggest that a competing theory requires attention. A theory of co-opting mother-infant bonding sometime in the recent evolutionary history of humans may partially account for the evolution of romantic love. I present a case for this theory and a new approach to the science of romantic love drawing on human psychological, neurobiological, and (neuro)endocrinological studies as well as animal studies. The hope is that this theoretical review, along with other publications, will generate debate in the literature about the merits of the theory of co-opting mother-infant bonding and a new evolutionary approach to the science of romantic love.

This study extends the emerging body of research on farmer adaptation to climate change, by segmenting farmers on the basis of specific attributes (health, values, belief about climate change, sense of responsibility for climate change, desire to change, social, human and financial capitals and farmer demographics) and considering such attributes as critical social aspects of the contextualized capacity to adapt. The segmental analysis was based on a nationally representative sample of 3,993 farmers concerned with farmer adaptation of climate risks. The resulting data were subjected to two-step cluster analysis to identify homogenous groups of farmers based on factors related to climate change adaptation. A three-cluster solution was identified wherein farmers were distinguishable on the basis of belief in climate change, desire for financial assistance and advice, social connectedness, information seeking, and adverse farm conditions. The largest group (Cluster 1: 55%) was characterized by farmers who recognized being affected by drought and drying and who were actively engaged in adaptive practices, despite the fact that they had little income and poor farm resources. One third of these farmers reported that their health was a barrier to sustained activity in farming. Cluster 2 (26%) was characterized by farmers not readily affected by drying, who enjoyed good incomes, good health and better farming conditions. They expressed little desire to adapt. The smallest cluster (Cluster 3: 19%) was also characterized by farmers who recognized that they were affected by drying. However, despite a desire to adapt, they had very little means to do so. They reported the poorest natural resources and the poorest health, despite being younger. The findings suggest that it is the intent to adapt, starting from where people are at, which is a more important indicator of the capacity to work towards sustainable practices than assets tests alone.

In this non-systematic review, we consider the sample reporting practices of 42 studies up to and including 2021 investigating the biological mechanisms of romantic love (i.e., 31 neuroimaging studies, nine endocrinological studies, one genetics study, and one combined neuroimaging and genetics study). We searched scientific databases using key terms and drew on our and other authors’ knowledge to identify studies that investigated the mechanisms associated with romantic love using neuroimaging, endocrinological, and genetic methods. Only studies with a group or entire sample experiencing romantic love were included. The aim was to collate all relevant studies and determine the comparability of studies and ability to assess the generalizability of findings. We summarize how these studies report sex/gender, age, romantic love, relationship duration/time in love, and sample descriptors. We then outline the case for promoting comparability and the ability to determine generalizability in future studies. The findings indicate a limited ability to compare studies’ samples or make an assessment of the generalizability of findings. Existing studies are not representative of the general population in a particular country or globally. We conclude by presenting ideas about how best to report sex, age, romantic love characteristics, relationship status, time in love, relationship duration, relationship satisfaction, type of unrequited love, sexual activity, cultural characteristics, socio-economic status, student status, and method-relevant descriptors. If our ideas are adopted, in part or in whole, we expect the comparability of studies to increase. Adopting our ideas will also make it easier to make an assessment of the generalizability of findings.

Background: Evolutionary selection pressures, most notably sexual selection, have created (and continue to sustain) many psychobehavioral differences between females and males. One such domain where psychobehavioral sex differences may be prominent is romantic love. The ways in which females and males may experience and express romantic love differently has been studied in psychology as well as in the arts down the ages; however, no studies have focused specifically on romantic love (i.e., passionate love) using validated measures of romantic love solely in people who are currently experiencing this form of love. Methods: This study investigated sex differences in features and aspects of romantic love among 808 young adults experiencing romantic love. Univariate and multivariate analyses were conducted to measure sex differences in the number of times participants had fallen in love, when they fell in love relative to when they started their romantic relationship (love progression), intensity of romantic love, obsessive thinking about a loved one, and commitment. Additional univariate comparisons were made for sex differences in Passionate Love Scale scores. Results: Univariate analyses showed that males had fallen in love a greater number of times than females. Males had also fallen in love more quickly than females. Females had higher intensity of romantic love, higher commitment, and higher obsessive thinking about a loved one than males. These findings remained robust in multivariate analyses, controlling for several variables believed to influence romantic love, with the exception of commitment, which was no longer significant when other variables were controlled for. Conclusions: The findings are considered with reference to the evolutionary theory of sexual selection. We suggest that the specific adaptive challenges faced by females and males in the evolutionary history of romantic love may contribute to sex differences in romantic love. The findings shed light on contemporary sex differences in romantic love, as well as the possible evolutionary history and evolutionary functions of romantic love.

This article provides a narrative review of what is known about romantic love and sleep variations and provides possible explanations for the association. Romantic love and sleep are described using a comprehensive, unifying framework advocated by Tinbergen. We summarise the findings of studies investigating the relationship between romantic love and sleep. Sleep variations are associated with romantic love in adolescents and young adults. We then detail some proximate mechanisms that may contribute to sleep variations in people experiencing romantic love before considering potential evolutionary functions of sleep variations in people experiencing romantic love. The relationship between symptoms of psychopathology and sleep variations in people experiencing romantic love is described. With the current state of knowledge, it is not possible to determine whether sleep variations associated with romantic love are adaptations or by-products of romantic love. We conclude by proposing areas for future research.