Viruses hold a special place in theories about the origins of life. They are incredibly simple things, just consisting of a protein coat (called a capsid) and some RNA (or DNA), and so intuitively they could be some of the earliest and simplest forms of life. On the other hand, viruses are obligate parasites – they cannot reproduce outside of a more complex host like a bacterium, plant, or animal. So the question remains, which came first: the parasite or the host?
Conventionally, biologists have assumed that the parasitic nature of viruses meant that they evolved after more advanced life forms. More recent discoveries of giant, complex viruses, however, have called this assumption into question. A new “Virus World” hypothesis suggests that viruses evolved before cellular life-forms and then guided the latter’s evolution. In this light, understanding how the first viruses came about becomes key to understanding the evolution of all modern life.
Now, a study published only this month in Nature promises answers to some of the more vexing questions about how viruses evolved. And amazingly, the researchers behind the study began with a very different goal : creating a better way of delivering vaccines.