So there are a number of studies on:
- encephalization within primates
- encephalization within vertebrates in general
- encephalization measured mathematically ("encephalization quotient").
Vertebrates are not the only members of Animalia that have brains. Arthropods and mollusks have them too, and if I'm missing a phylum or subphylum that contains them, let me know.
There seems to be no indication of which genes influence encephalization in various taxa and the mechanisms by which a loose collection of ganglia coalesce into a brain.
What can you tell me about this topic?
So the synapse appears to have something to do with it.
The ABC article seems to have a valid point about the evolution of nervous systems, but when one considers that the basal members of various phyla most likely did not have a brain (basal chordates being similar to Amphioxus, basal mollusks being similar to monoplacophorans bearing only a loose nerve ring with a loose collection of ganglia, and the earliest arthropods bearing similarly loose collections of ganglia, among the phyla in which brains developed), the article doesn't make sense. The ancestral bilaterian diverged, as far as I can tell, into Protostomia and Deuterostomia before brains coalesced.
The ScienceDaily article seems to be talking only about the CNS, which does not necessarily contain a 'brain'; it may just be a bunch of ganglia. I'm curious about how these ganglia formed brains.
Have either of you read "The Backbone of the Post-Synaptic Density Originated in a Unicellular Ancestor of Choanoflagellates and Metazoans" by Alie, A. and Manuel, Michael? It's a very insightful study on the evolution of the proto-neuron :]
I am not sure I would go so far as to claim an entire genus of single celled bacteria, as a proto-neuron.
My assumption is that ion channels, not just the sodium one, were already in existence long before neurons formed, as they have a role in the homeostatus of cells in general these first ion channel based cells, would have had pores with the equivalent of flood gates for nutrients, as described in this set of articles.
As a result, plant cells might have them as well.
Although I can't claim prior experience, evidence places the ganglion in the body of box jelly fish in a radial configuration, and in the body of the snail in a bilateral configuration that had about as many ganglions as the original jelly fish.
In essence the nearest I can make out, the jelly fish had a ganglion connecting its eye with its stinger for each segment of radial symmetry. If as I suggest the ganglions were conserved when we moved to bi-lateral symmetry, the number of senses that developed in the snail might indicate the degree of radial symmetry of the jellyfish ancestor.
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