Brett was born in Bozeman, Montana, while his parents attended Montana State University. He spent his early childhood in Seattle, where his brother was born. Shortly thereafter, his family moved to San Francisco and, eventually, Portland, Oregon.
His family spent many of their summers at a wheat and barley farm in Cascade, Montana, helping with the annual harvest. This experience was important to Brett. He fished for trout on the Missouri River by evening and drove grain trucks on the farm by day.
He went to high school in a Portland suburb. He continued to fish while in high school, but hung up his bait rig for a fly-fishing one. He also spent inordinate amounts of time white water kayaking on Oregon's coastal rivers.
Brett attended the College of Idaho, a small liberal arts college, to alpine ski race, but left skiing for academics his sophomore year, after he discovered a deep passion for history. After college, he traveled to Japan and Switzerland and eventually decided to study Japan's history, culture, and language.
Lured by promises of talented professors and fly-fishing on the McKenzie River, Brett attended the University of Oregon in Eugene to earn a PhD after graduating with an MA from Portland State University. His first academic job was as assistant professor of history at Yale University. Like a salmon, he later returned to Bozeman to teach at Montana State University.
Brett attributes much of his interest in the environment to a childhood spent outdoors. His research focuses on diverse peoples and the complex environments in which they are enmeshed. Whether a home for microbial diseases, industrial pollution, or clean water, the environments where people live flow through their porous bodies. Our bodies are products of these landscapes and their histories – fleshy relics of time-specific ideas and enterprises. For this reason, Brett has concentrated his research at the intersection of human health, environmental change, and the history of scientific ideas to better understand the global challenges that face humanity.