Jeff Leach’s interest in modern diet and the gut microbiome began more than a decade ago when his daughter was diagnosed with type 1 diabetes mellitus. Since then it has become increasingly clear that the gut microbiome plays a role in the development of type 1 diabetes mellitus, other autoimmune diseases, and modern (ecological) diseases of the Western world. In an effort to raise awareness about the changes in human ecology that have given rise to diseases of the so-called modern world, Jeff launched the Human Food Project (nonprofit, 501(c)(3)) to explore the microbiomes of indigenous populations in Africa and Mongolia. To further blur the line between microbiome science and the general public’s understanding of the role of microbes in health and disease, he cofounded the American Gut (http://www.americangut.org), the largest open-source/crowd-funded microbiome project in the world (also includes British Gut, Asian Gut, and Australian Gut). He has also recently cofounded UK-based MapMyGut (http://www.mapmygut.com) and is the author of Rewild.