Was Your Ancestor a Ball of Jelly? Evolution Study Surprises Experts
The question of whether sponges or comb jellies were the first animals to evolve continues to stir the waters.
While an argument over ancient ancestry may seem academic, it's an important question to answer because it influences how researchers think about the nature of animal evolution, said study co-author Andy Baxevanis, a geneticist at the National Human Genome Research Institute in Bethesda, Maryland.
Sponges are simple creatures, lacking muscles or a nervous system, he said, while comb jellies have both. (See a video on how comb jellies hunt.)
"There's been this long-standing tenet in evolutionary biology," Baxevanis explained, that once evolution led to "some kind of complex cell type—like musculature or an eye—you wouldn't lose it."
That's because keeping muscles or a nervous system would be a survival advantage.
But if comb jellies did in fact come before the simpler