The so-called "C-Value Paradox" was described over thirty years ago. Here's how Benjamin Lewin explained it in Genes II (1983).
The C value paradox takes its name from our inability to account for the content of the genome in terms of known function. One puzzling feature is the existence of huge variations in C values between species whose apparent complexity does not vary correspondingly. An extraordinary range of C values is found in amphibians where the smallest genomes are just below 109bp while the largest are almost 1011. It is hard to believe that this could reflect a 100-fold variation in the number of genes needed to specify different amphibians.Since then we have dozens and dozens of examples of very similar looking species with vastly different genome sizes. These observations require an explanation and the best explanation by far is that most of the genomes of multicellular species is junk. In fact, it's the data on genome sizes that provide the best evidence for junk DNA.
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