MTorrice writes: Our chromosomes hold a partial record of prehistoric viral infections: About 8% of our genomes come from DNA that viruses incorporated into the cells of our ancestors. Over many millennia, these viral genes have accumulated mutations rendering them mostly dormant. But one of these viruses can reawaken in some patients with amyotrophic lateral sclerosis (ALS), a progressive muscle wasting disease commonly known as Lou Gehrig's disease. A new study demonstrates that this so-called endogenous retrovirus can damage neurons, possibly contributing to the neurodegeneration seen in the disease. The findings raise the possibility that antiretroviral drugs, similar to those used to treat HIV, could slow the progression of ALS in some patients.