Possible Role of Non-coding DNAs in the Cambrian Explosion

The "Cambrian explosion" (CE) refers to a sharp increase in the number of fossils of living beings in the sediments of the Cambrian period (CP), which began 538.8 ± 0.2 million years ago and ended 485.4 ± 1.9 million years ago. It was in the CP that drastic changes took place in the biosphere: if before that almost all life was simple and unicellular, then after the CE there was a sharp increase in the number of complex multicellular organisms. However, the reason(s) for these drastic changes remains unknown. Various hypotheses were put forward: a sharp change in climate; the appearance of sexual reproduction; bilaterality or an increase in oxygen concentration that allowed the development of multicellularity. Apparently, the essence of the problem is to clarify the mechanisms and material basis of fundamental changes in the biosphere. For such an explosion, radical changes in the genome are necessary. It is suggested that the CE is associated with the evolution of the most mobile part of the eukaryotic DNA genome, rather than an increase in the number of previously existing or newly emerged genes. From our point of view, the evolution of non-coding DNAs, which make up the vast majority of DNA in the eukaryotic genome, could play an important role in the emergence of CE.