Life depends on genes being switched on and off at exactly the right time. Even the simplest living organisms do this, but usually over short distances across the DNA sequence, with the on/off switch typically right next to a gene. This basic form of genomic regulation is probably as old as life on Earth. A new study published in Nature by researchers at the Centre for Genomic Regulation (CRG) and the Centre Nacional d’Anàlisi Genòmica (CNAG) finds that the ability to control genes from far away, over many tens of thousands of DNA letters, evolved between 650 and 700 million years ago. It probably appeared at the very dawn of animal evolution, around 150 million years earlier than previously thought. The critical innovation likely originated in a sea creature, the common ancestor or all extant animals. The ancient animal evolved the ability to fold DNA in a controlled manner, creating loops in three-dimensional space that brought far-flung bits of DNA in direct contact with each other. The discovery was made by exploring the genomes of many of the oldest branches on the animal family tree, including comb jellies like the ‘sea walnut’ (Mnemiopsis leidyi), placozoans, cnidarians, and sponges and single-celled relatives of animals.

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