Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269-3125, USA.
Reconstructing the 'Tree of Life' is complicated by extensive horizontal gene transfer between diverse groups of organisms. While numerous conceptual and technical obstacles remain, a report in this issue of Journal of Biology from Koonin and colleagues on the largest-scale prokaryotic genomic reconstruction yet attempted shows that such a tree is discernible, although its branches cannot be traced.