Reminds me of the idea that at some point a pair of (relatively close in time) genome duplications gave rise to jaws, adaptive immune systems, and a bunch of ne

Reminds me of the idea that at some point a pair of (relatively close in time) genome duplications gave rise to jaws, adaptive immune systems, and a bunch of neuropeptides: "Nearly forty years ago, Susumu Ohno proposed that one or two rounds of whole genome duplication took place close to the origin of vertebrates. The refined version of this proposal, known as the two round (2R) hypothesis, assumes that the genome of jawed vertebrates has been shaped by two rounds of whole genome duplication that took place after the emergence of urochordates and before the radiation of jawed vertebrates. [...] Of special interest in this connection is the proposal of Olinski et al. [ 45••] that the four sets of MHC paralogons and the four sets of neurotrophin paralogons were derived from a single contiguous region on an invertebrate proto-chromosome (Figure 2). Interestingly, two of the neurotrophin paralogons [46] are located on 12p11–p13 and 19q13–q14 that encode the NKC and LRC, respectively." http://www.ncbi.nlm.nih.gov/pubmed/17707623 http://www.ncbi.nlm.nih.gov/pubmed/17707623