So we learn at New Scientist:
A comb jelly fossil from some 500 million years ago shows a previously unknown species of these ancient sea animals that had a more complex nervous system than their modern descendants.
Evolutionary theory doesn’t preclude the possibility of organisms becoming simpler over geological time, but it’s a relatively uncommon phenomenon.James Urquhart, “Ancient comb jelly had more complex nerves than its modern relatives” at New Scientist (August 14, 2021, The paper is open access.)
Well, it’s a good thing for “evolutionary theory” that it doesn’t “preclude” life forms becoming “simpler over geological time.” That’s called devolution and it is in fact very common.
In fact, as Michael Behe points out in Darwin Devolves, a great deal of “evolution” is simply breaking or blunting working machinery for an immediate advantage. That’s natural selection at work. The real natural selection, that is, not the Darwinians’ magical version.
If a comb jelly can survive while being less complex, it probably will. Being less complex may not be an advantage in the long run but natural selection is not about the long run. Natural selection is about the here and now — and can never be more than that.
See also: Genome Map Shows Comb Jellies Had Separate Course Of Evolution From Other Animals