After years of study, he thinks he knows why. According to traditional evolutionary biology, neurons evolved just once, hundreds of millions of years ago, likely after sea sponges branched off the evolutionary tree. But Moroz thinks it happened twice — once in ancestors of comb jellies, which split off at around the same time as sea sponges, and once in the animals that gave rise to jellyfish and all subsequent animals, including us. He cites as evidence the fact that comb jellies have a relatively alien neural system, employing different chemicals and architecture from our own. “When we look at the genome and other information, we see not only different grammar but a different alphabet,” Moroz said."
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