This week's NewScientist gives a rundown of some of the latest research into viruses [sub. req.]. The shorthand version: they play a much larger part in evolution than anyone has imagined.
[Patrick] Forterre and others have since built up evidence that early life was a period of wild biochemical experimentation in which molecular systems were constantly being invented and thrown together into new and increasingly complex ensembles (Virus Research, vol 117, p5). Once cells evolved, the experimentation continued, driven by innovation and gene transfer by the first viruses. The result was the creation of numerous alternative living systems, built up from random combinations of the available components. Only three of these systems survive to this day in the form of the three domains of cellular life; much of the rest lives on in the virosphere.Humans aren't immune (couldn't resist):
That puts viruses right at the heart of early evolution. "If you consider that viruses have always been more abundant than cells, you should conclude that the flow of genes has always been higher from viruses to cells," says Forterre. "Given this, it should not be surprising that major innovations could have occurred first in the viral world, before being transferred to cells."
ERVs have been known of since the 1970s, but the full extent of their infiltration did not become apparent until 2003, when genome sequencing revealed that our DNA is absolutely dripping with them. At least 8 per cent of the human genome consists of clearly-identifiable ERVs. Another 40 to 50 per cent looks suspiciously ERV-like, and much of the rest consists of DNA elements that multiply and spread in virus-like ways. Taken together, virus-like genes represent a staggering 90 per cent of the human genome.You may be the product of intelligent design. Thing is, the designers were viruses.