Could the brain have evolved from a parasitic organism?

Has anyone ever tried to explain where the organism of the brain came from?

I'm just speculating here but could the protobrain have started out as an organism that would attach itself to the inside of another organism and feed? And as this organism evolved it lost the ability for self-propelled movement? And is thought in the brain that long lost motive power turned in on itself? So instead of moving itself, it evolved thought and senses to better successfully direct it's host through its environment?

 

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You lost me at "organism of the brain" - I can't tell what your question is actually asking.

 

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The brain is an organism, right? If not, just ignore that part. I'm pretty sure it's an organism, though.

 

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The brain is an organ, not an organism.

 

Organisms that are more intelligent are more successful at reproducing, therefore the traits that enable higher intelligence are naturally selected or "evolved". I hope this adequately answers your question. If you have a more specific question about biology you can always message me

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We wouldn't say that an organism had "lost self propelled movement". Because we know that the only way this is possible is if this characteristic is removed from the gene pool (all carriers of the trait are deceased). If it had been removed from the gene pool, that is because a more effective mutation had made reproduction more likely - these small mutations are the first signs of what we call the "brain" which is obviously more complex now than during early stages of mutation. "self-direction" as you call it would require much more than a simple thought process (I know it's a bummer). It's easy to assume that an early brain was evolved to control movements - but the complexity of movement is mind boggling. Early intellect was likely first used as a way of determining sensory input, to signal if the organism was in danger. A system for self propulsion would require proprioception and an intricate motor system (which obviously doesn't happen in the first generation of mutations). Your theory about parasitic intelligence isn't necessarily unfounded, it's just not how the sequence of events would occur.

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Thank you for the detailed response.. Of course I'm sure you know it's more a hypothesis than a theory...I'm not sure why I latched on to the assumption the brain could have possibly been once a separate organism at one time in the distant past. Do you know if there are any verifiable animal organs now part of an animal that scientists think may have existed as a separate organism at one time? I'm thinking this might be more likely in an ocean going creature but I wouldn't really have any idea.

I should have also been more clear that I was implying all the necessary sequences of development would eventually be in place....thought alone could not suffice... I don't know...perhaps the early ancestor of the brain cell entered into a biological partnership with another species that could move but had no self direction...maybe the early brain cell latched onto the inside of this species and proceeded to increase it connections to its host over time until the ones that had more of an ability to warn or direct their host away from danger had a better chance of survival. Over time the brain and its accompanying appendages used to process external stimuli and direct action became more evolved and refined at controlling their host...?

 

On this you may be correct. I did not search much but recall that the PMW is thought to be a symbiotic relationship that has become permanent in a new creature. Why I quickly found this:

But, no the brain evolved with the rest of the organism we call apes (humans being one type). Even single cell amoebas have some capacity to sense their environment - will avoid light, for example. From there, refinements / increased complexity/ it is "all down hill" for evolution - the first hardest step is done.

 

I had a feeling I had heard about a sea creature that had evolved into itself from several other independent organisms. Of course, if this happened with the ancestor of the brain cell it was already fused permenantly with its host species long before humans showed up, or even mammals and we are only enjoying the results.

One of the problems with my hypothesis is that it presupposes in the parasitic ancestor of the brain cell a capacity it is not supposed to have yet and is supposed to explain.. If you can already feel as a way to find your host, you already have the rudimentary foundation for an organ that can send messages to other parts of a biological structure.

 

Organs that were once organisms? No, I can't say I've ever heard of that.

 

Billy T has provided the example of the Portuguese man of war.

 

They call these organs organisms because of their germ cell production - which isn't necessarily unheard of.

"Each gonophore has a central spadix of multinucleate endodermal cells separating the coelenteron from a layer of germ cells. Covering each germ cell is a layer of ectodermal tissue. When gonophores first bud, the germ layer is a cap of cells on top of the endodermal spadix. As gonophores mature, the germ cells develop into a layer covering the spadix. Spermatogonia form a thick layer, while oogonia form a convoluted band several cells wide, but only one cell layer thick. There is very little cytoplasmic material within these cells, except during rare instances when cell division is occurring. Oogonia begin development at approximately the same size as spermatogonia, but become considerably larger. All oogonia are apparently formed at an early stage of gonophore development prior to the occurrence of enlargement. Interestingly, there appears to be yolk globules within the cytoplasm of most oogonia."
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I'm going to assume that the sexual representation(germ cells) of 'organisms' within the man-a-war is because the man-a-war itself is unable to replicate without them. To say that their organisms were at one time another entity altogether is speculation that only the fossil record could prove.

http://biology.stackexchange.com/qu...-any-organs-start-out-as-autonomous-organisms

 

You may want to look into symbiogenesis.

http://en.m.wikipedia.org/wiki/Endosymbiotic_theory

 

That was easier to follow than I expected for what seems an infinitely complex subject. . I can't imagine how difficult it is for the people tasked with figuring this all out... Thank you ...

 

You may want to read Hothouse by Brian Aldiss.

 

I've never read it as I don't read much fiction...Do you consider it that good a work of science fiction that it would shed light on this subject?

 

It's pretty good. And it considers the issue of brains as symbiotic organisms. I doubt that the idea is possible, so this book might be the closest thing to serious consideration you'll find.

 

I raised honey bees, for two summers and the winter between - very interesting project and read several books on them. The individual bee is most accurately viewed as a specialized organ in the organism called a bee hive, not an organism by its self. These organs not only do specific jobs but communicate information, and not just by "dance" that tells where newly discovered good food source is, but by chemical exchanges like the organs of your body do.

If the queen is removed, not much happens for about an hour. The "essence of queen" chemical level in the fluids they exchange is OK, but when it falls too low, all hell breaks out. Frantic recovery of larva still in stage that they can develop into queens, new larger wax cell are built, and selected larva moved into them and feed "royal jelly" etc.

Also if you watch the landing platform of the hive, most bees returning will be greeted with some sort of chemical test to make sure they are not from another hive, coming to try to steal honey or pollen. One of the specialized duties is guard duty. Another is ventilation duty, on hot days. They may have more specialized organs than humans do!

My hive was on a wooded lot I owned and I would go there to cut up fallen limbs, etc. in late summer for my fire place. In a book I had learned that bees could be marked with a little white flour. So first thing I did when arriving was to mark a couple that were stationary with wings furiously beating just at the entrance slot of the hive. A couple of hours later when I had nice load of wood in my pick-up truck I went back to look. Both bees were still there, with feet locked into paint or a crack, I could not see, still doing their "ventilation duty" as assigned.

 

There's a whole specialty of the biological sciences devoted to that kind of thing: developmental biology. This science studies how organisms' anatomies differentiate and develop, from fertilized-egg to adult.

That's kind of a cool idea, the idea that we (our intelligence and awareness at least) are the result of parasites (or more accurately symbionts) that took up residence in early animals.

It would have had to have been a very early animal, since virtually all animals have nervous systems clumped into brain-like ganglia, at the least. What kind of free-living organism would have been the ancestor of nervous systems?

A pretty strong argument against this theory is the fact (at least I think it's a fact) that the cells of the human nervous system share precisely the same genome as the rest of the human organism. If they had a different ancestry, we'd expect to see residual genetic differences. It's interesting in that regard that mitochondria (little power-generating organelles inside eucaryotic cells) are believed to be the descendents of symbiotic bacteria and they still have their own mitochondrial DNA separate from that of the chromosomes in the cell nucleus.

Ok, if they aren't symbionts, where do brains come from? Developmental biology reveals that very early embryos develop three tissue layers that are the predecessors of skin, muscle and gut cells. Then among the chordates at least, this very early skin layer develops a groove on its surface that grows deeper and deeper. Eventually the top edges of this groove meet and reseal, leaving a tube of skin cells under the surface, that start turning into nerve cells, becoming the spinal cord, brain and peripheral nerves.

http://en.wikipedia.org/wiki/Neural_tube