h/t to fBast: “Ooooh, stop the presses! New thread, somebody? See: Origin of Nerves traced to Sponges, it seems that sponges don’t have nerve cells, but they know how to grow ‘em. This smacks very loudly of front-loading.”
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Abstract:
“We are pretty confident it was after the sponges split from trunk of the tree of life and sponges went one way and animals developed from the other, that nerves started to form,” said Bernie Degnan of the University of Queensland. “What we found in sponges though were the building blocks for nerves, something we never expected to find.”
In humans and other animals, nerves deliver messages to and from the brain and all the parts of a body.
Degnan and colleagues studied a sea sponge called Amphimedon queenslandica. “What we have done is try to find the molecular building blocks of nerves, or what may be called the nerve’s ancestor the proto-neuron,” Degnan said. They found sets of these genes in sponges.
“But what was really cool,” he said, “is we took some of these genes and expressed them in frogs and flies and the sponge gene became functional — the sponge gene directed the formation of nerves in these more complex animals.
Sponge Genes Provide New Insight into the Evolutionary Origin of the Neurogenic Circuit Gemma S. Richards, Elena Simionato, Muriel Perron, Maja Adamska, Michel Vervoort, and Bernard M. Degnan Current Biology Volume 18, Issue 15, 5 August 2008, Pages 1156-1161