The discovery of a megavirus

The discovery of a megavirus is confirmation that giant viruses descended from complex cells that became simpler.

Since the discovery of the first giant virus, mimivirus, in 2003, researchers have debated how they evolved. Unlike conventional viruses, mimivirus carriesmany genes thought to be unique to cellular life, suggesting that it evolved from a cell. But it could also have stolen those genes from cells that it infected.

The new giant virus, dubbed megavirus, is 7 per cent larger than mimivirus. It was found by Jean-Michel Claverie of the Structural and Genomic Information Laboratory in Marseille, France. It is a distant relative of mimivirus, sharing all its cell-like genes. Claverie says this is "definitive proof" of a cellular ancestor.