Notorious for making us sick, viruses are weird, undead organisms – but new insights are revealing they may have created life’s glorious complexity in the first place
IMAGINE an alien creature floating in space. It doesn’t grow, communicate or move at all under its own steam. Without a home it is inert. We know very little about it, except that it will start reproducing when it enters the atmosphere of a planet that suits it. Is it living? Is it dangerous?
This may not sound like a plausible being, but it pretty much describes viruses, which are little more than bits of genetic material able to replicate only when inside a host. Viruses may seem alien, but they are the most abundant and, arguably, the most important organisms on Earth. They are found just about everywhere, from oceans and forests to the people around you and, of course, in and on you as well. This world of strange, quasi-living things has been dubbed the virosphere, and it is a mysterious one – we know less about viruses than any other life form. But that is changing rapidly.
People generally view viruses as synonymous with infection, and there is no doubt they cause some of the most dangerous diseases, including smallpox, AIDS, Ebola and flu. Yet viruses are so much more than indiscriminate killing machines. Our ability to inspect the genetic material they are made of has improved exponentially and, in the past five years, the number of species identified has increased 20 fold. What’s more, it is becoming increasingly clear that these bizarre and diverse organisms play a key role in evolution and may well have been crucial for the origins of life.