How does the vast, invisible ecosystem of microbes living within the human body dictate our physical health, mental state, and susceptibility to chronic disease? Alanna Collen, a biologist with a background in evolutionary biology, synthesizes current research on the human microbiome to argue that we are far more bacterial than human. She examines how modern lifestyle choices, including diet and antibiotic overuse, disrupt these internal communities and contribute to a range of contemporary health crises.

The text provides a comprehensive and accessible overview of the microbiome, suitable for readers interested in the intersection of biology and public health. Its focus on the evolutionary implications of our microbial dependencies offers a clear framework for understanding the consequences of modern medical interventions.