So to be crystal clear: everything out there is influencing the evolution of everything else. The bacteria and viruses and parasites that cause disease in us have affected our evolution as we have adapted in ways to cope with their effects. In response they have evolved in turn, and keep on doing so. All kinds of environmental factors have affected our evolution, from shifting weather patterns to changing food supplies—even dietary preferences that are largely cultural. It’s as if the whole world is engaged in an intricate, multilevel dance, where we’re all partners, sometimes leading, sometimes following, but always affecting one another’s movements—a global, evolutionary Macarena.

From Survival of the Sickest: The Surprising Connections Between Disease and Longevity.