 These discussions of genome sizes were closely related to concerns about gene numbers. And this consideration of genome size vs. gene numbers is what originally gave rise to the concept of ‘junk DNA’ (Ohno  1972).[11]  The reasoning behind this concept was the following: if one assumes a) that more complex organisms will have more DNA than less complex organisms and b) that gene numbers increase in proportion with genome size, then the genome of the more complex organism should have more genes than the less complex  one.[12]  Human cells, for instance, contain about 750x more DNA than E. coli, meaning that they should turn out to have in the range of 3.7 million genes, as E. coli has about 5000 genes. This is clearly not the case; even in the 1970s it was generally supposed that the human genome might contain no more than 150,000 genes (Crollius et al. 2000). This discrepancy leads to the conclusion that the vast majority of the DNA in our genome cannot be genes and is therefore what Ohno referred to as  ‘junk’.[13]