Depression is often linked to adversity: why would it reliably appear in such conditions? Ed Hagen has spent over forty years wondering about this question, and is one of the world's foremost researchers on evolutionary approaches to depression. We discuss depression in this interview. Ed Hagen is a Pofessor of Evolutionary Anthropology at Washington State University. Professor Hagen began his academic career with a BA in mathematics from UC Berkeley and initially worked in an organic polymer lab before discovering his passion for anthropology. This led him to pursue a Ph.D. in anthropology at UC Santa Barbara, where he graduated in 1999. Following his doctoral studies, he joined Peter Hammerstein’s group at the Institute for Theoretical Biology at Humboldt University in Berlin. Since 2007, Dr. Hagen has been a faculty member at Washington State University, where he directs the Bioanthropology Lab. Dr. Hagen’s research explores evolutionary medicine, particularly focusing on non-infectious diseases—a field where traditional medicine has seen limited breakthroughs. His studies encompass various aspects of mental health, examining conditions like depression, suicide, and self-harm through the lens of evolutionary signaling strategies. He has also explored the complex dynamics of tobacco use and human interactions with plant secondary compounds, child growth and development (stemming from his research on postpartum depression), and more recently, evolutionary models of leadership and knowledge specialization. To connect with Dr. Hagen’s ongoing work, check out his blog at grasshoppermouse.github.io or follow him on Twitter at @ed_hagen and on Mastodon at @edhagen@fediscience.org.