A jelly-like sea creature may have evolved a nervous system before every other animal
Comb jellies glide using thousands of beating cilia rather than muscles, and genome studies suggest their lineage may have split off from the rest of the animal kingdom even earlier than sponges did — which would make their nervous system either the oldest one alive today, or evidence that neurons evolved more than once, independently. Some species even appear to build two separate, differently-wired nerve nets in a single body.