As with the larger environment in which we live, our internal microbiome is at risk of extinction. A new study shows that we have lost many of the organisms that we co-existed with a millennium ago. How can we restore this diversity? Doctors and others are examining the evidence of how a healthier, more diverse gut may help us avoid chronic conditions such as diabetes and obesity. Science is learning more about pre-industrialized humans in the hope that it may be possible to restore some of the lost microbiome, and improve our balance in the modern world.