High Quality Content by WIKIPEDIA articles! The 2R hypothesis or Ohno`s hypothesis, first proposed by Susumu Ohno in 1970, is a contested hypothesis in genomics and molecular evolution suggesting that the genomes of the early vertebrate lineage underwent one or more complete genome duplications, and thus modern vertebrate genomes reflect paleopolyploidy. The name derives from the 2 rounds of duplication hypothesized by a 1994 version, and the term 2R hypothesis was probably coined in 1999; variations in the number of duplications typically still are referred to as examples of the 2R hypothesis. Since Ohno proposed the first version of it in Evolution by Gene Duplication, the 2R hypothesis has been the subject of much research, but even with recent data from the human genome, it remains a matter of scientific dispute.