Question: where do viruses come from

Sara Imari Walker answered on 17 Jun 2011:

Viruses are so cool!! I was at a conference last week, and met a virus expert there. I was practically stalking the guy, I was so excited to learn more about them!! Lol.

The interesting thing is that we are not really sure where viruses come from. They are made of the same molecular machinery as we are – based on DNA with a protein coat usually. That’s why they cause us trouble. Since viruses are so primitive, being only a tiny strip of coding DNA plus some extra stuff, it has been suggested that they are very ancient. Maybe even playing a role in the origin of life.

However, viruses require the same complex copying machinery that every living thing on Earth requires. They NEED cells to reproduce, they are nothing without cells. Therefore a lot of people are starting to think viruses evolved much later in the history of life on Earth. Bacteria often exchange chunks of DNA, called mobile genetic elements, through a mechanism called horizontal gene transfer. Basically in a pool of bacteria, there is a bunch of DNA floating around which bacteria can pick up and incorporate into their own genome (they can also add genes to this pool). So, viruses may be an evolved form of these mobile genetic elements that gained some autonomy and became their own entities.

These are very different hypotheses, and the truth is we don’t know which may be right!! They may both be wrong. We still have a lot to learn. Really great question taljeda!