Re: News: Humans and sponges may share a slimy ancestor

On Jan 29, 4:04=A0pm, "Robert Karl Stonjek" <rston...@xxxxxxxxxxxxxx>
wrote:

If they're true, the findings have a difficult implication for many
biologists: they suggest that the nervous system evolved twice in two
separate systems. Placozoa and sponges don't have a nervous system, but t=
he
related cnidarians - which include jellyfish - do.

I propose that the nervous system evolved once, but crossed
clades by horizontal gene transfer. Maybe the nervous system evolved
first in cnidarians, and crossed into the triblastic animals via a
virus. Or maybe the other way. A protocnidarian without a nervous eats
something with a nervous system and accidentally incorporates its DNA.
I would be interested if the genes coding for acetylcholine are
the same in all clades. Acetylcholine is a venom in cnidarians. It
stings because it is a neurohumor in higher forms of life.
Acetylcholine is a complicated protein. If cnidarians and humans share
the same neurohumors, then I would have to say that the nerve cell is
a primitive feature.

.

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