For evolutionary biologists, what most distinguishes the marine creatures called cnidarians and ctenophores is not the peculiar spelling of their names, nor the fact that they tend to be beautiful, but that they are among the oldest known groups of complex animals. Cnidarians (the “c” is silent) include jellyfish, corals and sea anemones, and their colorful tendrils and fronds adorn oceans all over the globe. Ctenophores (another silent “c”), otherwise known as comb jellies, are mostly translucent and gelatinous, and they pulse through the marine world like ectoplasm.
Thought to have arisen between about 740 million and 520 million years ago, both phyla of marine invertebrates were among the first multicellular animals to evolve several different tissue types. Their appearance ramped up the complexity of the animal world: They are more similar to us in terms of size and organization than they are to the single-celled organisms that came before them. The evolutionary debut of cnidarians and ctenophores thus represented one of the most significant steps in the journey from primordial slime to humans.
What made it possible?
Sebé-Pedrós and his colleagues believe that what made these new patterns of gene regulation and expression possible in the earliest complex animals was a rather bizarre gambit that all multicellular creatures now employ. It involves pulling loops of DNA out of the tangled mass of the chromosomes, and letting the loops undergo topologically complicated contortions to put one part of the chromosome in contact with other parts far away. The origin of animal complexity might literally have been loopy.
Quanta Magazine
For evolutionary biologists, what most distinguishes the marine creatures called cnidarians and ctenophores is not the peculiar spelling of their names, nor the fact that they tend to be beautiful, but that they are among the oldest known groups of complex animals. Cnidarians (the “c” is silent) include jellyfish, corals and sea anemones, and their colorful tendrils and fronds adorn oceans all over the globe. Ctenophores (another silent “c”), otherwise known as comb jellies, are mostly translucent and gelatinous, and they pulse through the marine world like ectoplasm.
Thought to have arisen between about 740 million and 520 million years ago, both phyla of marine invertebrates were among the first multicellular animals to evolve several different tissue types. Their appearance ramped up the complexity of the animal world: They are more similar to us in terms of size and organization than they are to the single-celled organisms that came before them. The evolutionary debut of cnidarians and ctenophores thus represented one of the most significant steps in the journey from primordial slime to humans.
What made it possible?
Sebé-Pedrós and his colleagues believe that what made these new patterns of gene regulation and expression possible in the earliest complex animals was a rather bizarre gambit that all multicellular creatures now employ. It involves pulling loops of DNA out of the tangled mass of the chromosomes, and letting the loops undergo topologically complicated contortions to put one part of the chromosome in contact with other parts far away. The origin of animal complexity might literally have been loopy.
🧬 Read the full story: www.quantamagazine.org/loops-of-dna-equipped-ancie…
🎨 Myriam Wares for Quanta Magazine
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