Recent evidence of horizontal gene transfer -- in which genes are exchanged from other organisms, not from ancestors -- has some scientists thinking that the dominant form of evolution for most of the Earth's history was between non-related organisms and not among ancestors.
In the past few years, a host of genome studies have demonstrated that DNA flows readily between the chromosomes of microbes and the external world. Typically around 10 per cent of the genes in many bacterial genomes seem to have been acquired from other organisms in this way, though the proportion can be several times that. So an individual microbe may have access to the genes found in the entire microbial population around it, including those of other microbe species. "It's natural to wonder if the very concept of an organism in isolation is still valid at this level," says Goldenfeld.
Read on for their hypothesis about how horizontal evolution drove innovation -- development of a universal genetic code and genetic innovation-sharing protocols -- in life forms early on in the Earth's history. Fascinating.