Reply #3: They are on the edge of life [View All]

[Ichingcarpenter]

Whether or not something reproduces is a factor in determining life, but it's not the only one. Crystals, for example, will form on their own and nucleate new crystal formation, but they're not alive. Viruses aren't alive because they can't replicate on their own, and have none of their own internal processes - they need to hijack a host cell.

Viruses are most often considered replicators rather than forms of life. They have been described as "organisms at the edge of life",since they possess genes, evolve by natural selection, and replicate by creating multiple copies of themselves through self-assembly. However, viruses do not metabolise and require a host cell to make new products. Virus self-assembly within host cells has implications for the study of the origin of life, as it may support the hypothesis that life could have started as self-assembling organic molecules

http://en.wikipedia.org/wiki/Life