An Elegant Defense: The Extraordinary New Science of the Immune System: A Tale in Four Lives

by Matt Richtel

Then about 500 million years ago, a split occurred, resulting in what would evolve into two major immune system lineages. One lineage belongs to non-jawed vertebrates, such as the lamprey and the hagfish. They developed a defense network that is both fundamentally different from ours and nearly as sophisticated. By comparison to ours, theirs is like an ancient language with different lettering, an alternate scripting of the genetic code that confers many of the same defense advantages. Twenty million years later, around 480 million years ago, the other lineage finds its roots. We know this because creatures that lived that long ago, like the shark, rely on this second lineage. And so do human beings. In the most fundamental sense, we share an immune system with sharks and other jawed vertebrates.