Cohort studies are essential for conducting large studies of multiple exposures and outcomes in humans. Recently, the ability to combine data from multiple cohorts in, for example, meta-analyses, and the willingness in the genetics community to collaborate to enable replication studies has led to many new insights into the genetic and environmental determinants of human health and behaviors. The contribution of Professor Nicholas Martin to the development of cohort studies, particularly of twin and twin-family studies, over a period of several decades is reviewed. He has contributed to the development and use of both Australian and international resources. The contributions of Australian twin studies to genomewide association projects are multiple, and across multiple domains, from biomarkers, lifestyle and behavior to disorders and disease.

Genetic research into human sexuality was scarce at the end of last century. In 1992 Nick developed a 12-page questionnaire to send to twins to investigate the underpinnings of sexuality. The questionnaire included items about sexual orientation, sociosexuality and sexual behavior, and was completed by almost 5000 twins. The resulting data, unique at the time, has been used to investigate many previously unexaminable research questions. Here we describe how Nick’s questionnaire contributed to our understanding of human sexuality and how we got involved in this endeavor.

I write this commentary as a part of a special issue published in this journal to celebrate Nick Martin’s contribution to the field of human genetics. In this commentary, I briefly describe the background of the Yang et al. (2010) study and show some of the unpublished details of this study, its contribution to tackling the missing heritability problem and Nick’s contribution to the work.

Nicholas Martin’s contribution to science is well known. This article reviews one small part of his pioneering work that integrated political and social attitudes with behavior genetics. Nick Martin, in part, led to a paradigm shift in the social sciences, and in political science in particular. These fields were previously wed to behavioralist approaches and now routinely include genetic influences in both theoretical and empirical study. This article also celebrates a part of Nick’s contribution that many do not know. Nick Martin does not just build science, he builds scientists. There are many who would not be academics or scholars without Nick’s guidance, mentorship and friendship. This review was written to express the deepest appreciation for what he has done and continues to do for science and the scientist.

This paper is about Nick’s contribution to the field of taste genetics, how I became involved and how a study on the genetic association between the perception of sweetness and bitterness ended up examining the influence of intelligence on taste perception.

Professor Nicholas (Nick) Martin spearheaded initial investigations into the genetic basis of political attitudes and behaviors, demonstrating that behaviors that are perceived as socially constructed could have a biological basis. As he showed, the typical mode of inheritance for political attitudes consists of approximately equal proportions of variance from additive genetic, shared environmental and unique environmental sources. This differs from other psychological variables, such as personality traits, which tend to be characterized by genetic and unique environmental sources of variation. By treating political attitudes as a model phenotype, Nick Martin was able to leverage the unique pattern of observed intergenerational transmission for political attitudes to reexamine the quintessential assumptions of the classical twin model. Specifically, by creatively leveraging the nuances of the genetic architecture of political attitudes, he was able to demonstrate the robustness of the equal environments assumption and suggest corrections to account for assortative mating. These advances have had a substantial impact on both the fields of political science, as well as behavioral and quantitative genetics.

Professor Nicholas G. Martin, from QIMR Berghofer Medical Research Institute in Brisbane, Australia, is a world leader in the effort to understand the genetic architecture underlying disordered gambling. This article pays tribute to Nick and his almost two decades of gambling research, highlighting his many strengths, ranging from the use of ingenious recruitment approaches, twin study methods, genomewide association studies, to facilitating international collaborations.

The International Cannabis Consortium (ICC) was founded in 2013 by Jacqueline Vink, Nathan Gillespie, Karin Verweij and Eske Derks. The largest contribution to the first meta-analysis was made by Prof. Nick Martin. The ICC has published two primary publications, in Translational Psychiatry and Nature Neuroscience, and many secondary publications. The study’s principal investigators will always be grateful for Nick’s contribution to science as they would not have been able to do any of this work without the contributions of Nick and others who collected samples. Nick has made unique contributions to the careers of many junior researchers by supporting their development and growth into senior positions.

The study and identification of genotype–environment interactions (GxE) has been a hot topic in the field of human genetics for several decades. Yet the extent to which GxE contributes to human behavior variability, and its mechanisms, remains largely unknown. Nick Martin has contributed important advances to the field of GxE for human behavior, which include methodological developments, novel analyses and reviews. Here, we will first review Nick’s contributions to the GxE research, which started during his PhD and consistently appears in many of his over 1000 publications. Then, we recount a project that led to an article testing the diathesis-stress model for the origins of depression. In this publication, we observed the presence of an interaction between polygenic risk scores for depression (the risk in our ‘genotype’) and stressful life events (the experiences from our ‘environment’), which provided the first empirical support of this model.

Identification of genetic variants associated with eating disorders is underway. The Anorexia Nervosa Genetics Initiative, an initiative of the Klarman Family Foundation, has contributed to advancing the field, yielding a large-scale genome-wide association study published in Nature Genetics. Eight genetic variants significantly associated with anorexia nervosa were identified, along with patterns of genetic correlations that suggest both psychiatric and metabolic origins of this serious and life-threatening illness. This article details the role of Professor Nick Martin in contributing to this important collaboration.

I recount early formative experiences with my father, Nick Martin.

This article opens with the brief life histories of reared-apart monozygotic (MZ) male twins. A New York City program that helped childless couples conceive via artificial insemination from the 1930s to the 1950s is examined as it related to these twins. The frequency with which pregnancies following assisted reproductive technology resulted in MZ twin pairs is also provided. Next, summaries of twin research concerning selective resuscitation, gene editing, sexual arousal and jejuno-ileal atresia are presented. The article ends with media reports of twin girls’ efforts to find a bone marrow donor for their father, possible parasitic twinning in a puppy, identical female twins’ business venture, the surgical separation of craniopagus twins, a twin-themed magazine cartoon and tragic events involving identical male twins.