The human genome has around three billion base pairs of DNA, and yet our best estimates are that this massive amount of DNA only includes about 20,000 protein-coding genes. These genes amount to a mere 1.5% of the total genome. Scientists have known that some portion of the remaining “non-coding” DNA has regulatory functions but the vast majority of the genome appeared to have no function. When I started a PhD program in molecular biology in 1992, the functionless DNA was sometimes called, “junk DNA” and was considered an artifact of evolution. “No intelligent being would make a genome this inefficient” was a common refrain.
Nearly twenty-five years later it turns out that “junk” is just another name for our ignorance.