The only kinds of ways we have to deal with viruses are old school, so vaccines for example are very effective, but the first vaccines were invented in the 1700's, so we're talking about technology that is over 200 years-old.
Carl ZimmerEvolution has led to some populations of people being able to digest milk without much trouble when they're adults as well.
Carl ZimmerAbout 1.2% of the human genome is made up of genes, things that encode for proteins, the stuff that we consider us. There is about 8.3% that's a virus. In other words we're probably about seven times more virus than we are human genes, which is kind of a weird way to thinking about yourself.
Carl ZimmerParasites are not only incredibly diverse; they are also incredibly successful. There are parasitic stretches of DNA in your own genes, some of which are called retrotransposons. Many of the parasitic stretches were originally viruses that entered our DNA. Most of them don't do us any harm. They just copy and insert themselves in other parts of our DNA, basically replicating themselves. Sometimes they hop into other species and replicate themselves in a new host. According to one estimate, roughly one-third to one-half of all human DNA is basically parasitic.
Carl Zimmer