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I'm curious about the origin of the neural network.

I'm thinking perhaps once life evolved beyond the single cell organism, it needed a simple neural network to coordinate those cells, and cell functions.

What were the first neural systems like?

More specifically: What kind of cell did the first neurons evolve from and how did they work at first? (assuming there were few, if any, neural connections in the first organisms to develop neurons of some sort)

From what I understand about a neural system, it needs a few neurons linked together to keep firing.

Perhaps the first neurons had triggers other than dendrite connections?

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  • $\begingroup$ I think this is too broad, since you are basically asking about the evolution of nervous systems (in any type of organism?), and there are multiple questions rolled into one. Also, why do you think that single neurons would be useless? They could still transfer information between cells (e.g. sensory/environmental input to motor action). Wikipedia: Evolution of nervous systems will also answer/hint at some of your questions. $\endgroup$ – fileunderwater Jan 20 '15 at 15:09
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    $\begingroup$ @file I'll focus the question. $\endgroup$ – CuriousWebDeveloper Jan 20 '15 at 15:11
  • $\begingroup$ I think this question is unanswerable as neural tissue is not preserved in fossils. Looking at relatively 'simple' organisms may help to get an idea. For example the neural system in cephalopoda (various ganglions throughout the body each driving one tentacle etc) or in insects. $\endgroup$ – AliceD Jan 21 '15 at 0:30
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    $\begingroup$ @ChrisStronks We know tons about evolution that isn't preserved at all in the fossil record. For instance, we can study evolutionary model organisms and do comparative genomics. In fact, fossils play a fairly minor role in the modern study of evolution. $\endgroup$ – Konrad Rudolph Jan 21 '15 at 9:02
  • $\begingroup$ @KonradRudolph : sure, that's what I say, perhaps use insects or other organisms. And if there's tons of info on the first neural systems I am curious to your answer! $\endgroup$ – AliceD Jan 21 '15 at 9:07
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This question can be answered by taking a look back evolutionary and see how other organisms have utilized neurology. The prime example, because it was one of the first real models of the neurological system, is the squid. It has neurons with singularly long axons to send electrical pulses long distance. This method of electric pulse transfer has been evolutionary updated, essentially, but we can get an idea of how these cells came to be. If we look back at squid predecessors, like the jellyfish, we see that it also developed electrical impulse cells to aide in defense and movement. Back further, we see the sponge has no neurons, but has something similar. This gives us potential insight into the development of the cell. It has protein clusters that act similar to post-synaptic signaling. So it is likely the electrical impulses were developed based on the function of these protein clusters, and bam! Electrical pulses became a must faster way to communicate to different regions of a system than simply trying to protein signal across cells.

Of course, looking at this question evolutionary is tricky since the question of divergent evolution comes into play, and we can't know if the sponge protein clusters offer a potential answer to neuronal development. But, is interesting evidence and makes an interesting debate!

Source= Sakarya O, Armstrong KA, Adamska M; et al. (2007). Vosshall, Leslie, ed. "A post-synaptic scaffold at the origin of the animal kingdom". PLoS ONE

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    $\begingroup$ I would really emphasize how limited our conclusion can be through looking at current organisms. Yes we can say one organism may be "higher level" than the other, but knowing exactly what the primitive state was? That is most likely something we will never truly know. Perhaps when we can finely simulate evolution through computers. An interesting new advancement has been the creation of circuit boards using algorithms for evolution. Essentially the circuits that are less efficient die out. $\endgroup$ – FrankyG Dec 10 '15 at 21:22
  • $\begingroup$ I agree! New networking algorithms offer interesting new insight to these types of questions (and many others!). I actually am currently working on developing such algorithms for alternative toxicity testing methods! It's crazy the diversity of uses of different tools, right? $\endgroup$ – ephackett Dec 11 '15 at 0:57
  • $\begingroup$ @FrankyG this ironic thing is, the use of algorithmic evolution of a brain was my purpose for asking this question to begin with. I've been experimenting with throwing out random configurations of tens of thousands of neurons of virtual neurons, which behave in a similar way to actual neurons, and let the ones die which arent capable of overcoming a pre-defined environment. This is a vague experiment at this point, and it hasnt gotten anywhere, because I think I need to start smaller, simulating an extremely primitive small group of neurons accomplishing a simple task. $\endgroup$ – CuriousWebDeveloper Mar 2 '16 at 2:17
  • $\begingroup$ But the issue with that is, our modern day neurons seem to be fairly useless in small groups. Theoretically, being able to figure out how the most primitive group of neurons worked would allow a good starting point for the evolutionary model. $\endgroup$ – CuriousWebDeveloper Mar 2 '16 at 2:18
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    $\begingroup$ You can further add variation to this by having the type of connections created be varied. You'll have to do some more research on specific neurology though as there are several different types of connections neurons can make to one another and it affects not only the speed of the signal but the strength when it arrives and how that signal propagates, reaches threshold, etc etc. $\endgroup$ – FrankyG Mar 3 '16 at 19:14

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