Muscles or Skeletons?
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As far as I remember, invertebrates existed before vertebrates, so muscles came first.
https://www.youtube.com/watch?v=gZpsVSVRsZk
Well being invertebrate doesn't necessarily imply muscles. Sagan's clip does a huge jump at 2:00, from filter-feeding organisms attached to the ocean floor, to freely swimming organism with backbones.
I'm not implying that all invertebrates have muscles. But still, they came before vertebrates and there are invertebrates with muscles. There are still some today. So the implication is that muscles came before skeletons.
I think your implication is a fair assumption. It just lacks the details I would like. Most invertebrates I can think of wouldn't benefit from a backbone. Give a worm or a squid a backbone and they might not be able to move at all unless its segmented and you rearrange all its muscles.
Fine, lets suppose muscles and invertebrates did come first. My follow up, once more, would be what came first then? Muscles or the nervous system/nerve net?
Hey, @John, and what do you think it developed first then? Muscles or the nervous system/nerve net? Intuitively, I'd say the nerve net, at least, what it's needed to move to coordinate those muscles and bones.
You know for certain I'm not a scientist, but based on human fetus' development, I'd say: On the 4th week of pregnancy, there are 3 layers of cells, one of them, the "mesodermo" (I couldn't find the English translation), is the one which will develop into muscles and bones, so this makes me think that maybe they're formed more or less, at the same time. And this is another clue to think the neural system is a previous requirement to develop them.
I think that's a valid hypothesis, but you need to be careful when comparing evolution to embryonic development. The mesoderm does develop into the muscles and skeletal system, but it develops at the same pace as the ectoderm, from which the nervous system develops. The end result is a spine with a spinal chord locked inside, with nerves that extend out into the muscles, which are attached back to the spine.
However, in terms of evolution, I don't know what the purpose of a nervous system without muscles would be. Perhaps sensation, but the purpose of sensation is to inform movement.
John, you need to be careful when comparing evolution to embryonic development You're right, I used it just an example to back my intuition up.
what the purpose of a nervous system without muscles would be. I don't know either, but take a look at "Cnidaria" animals... They have a "mesoglea" instead of a body, neither bones nor muscles yet they have a nervous system.
P.S. Cnidaria could also lead to think that neural net comes first.
(edited)
Right, cnidaria includes the jellyfish. They are the ones known to have the neural net, and you're right they don't have muscles exactly. However, the purpose of the neural net is still movement.
Jellyfish are a contemporary of ours. They're at the cutting edge of evolution just like us. Do you think we evolved from cnidarian-type species?
Do you think we evolved from cnidarian-type species? Maybe not directly, but I guess metazoa could be a common ancestor of both.
P.S. I mean eumetazoa.
Alright, well at least your answer makes sense theoretically.
Why don't you tell us your theory, John? I'm really curious and I'm sure you know more about evolutionary changes than I do (despite you feel the need to add God into all of this).
I mean my theory is that all three things are simultaneously necessary. If someone tells me all three evolved at the same time, it would at least make physiological and anatomical sense. You have the neuromuscular junction between muscles and nerves. The nerves release acetylcholine, and the muscles respond to it. The muscles are attached to the bones, to allow movement, the bones protect the nerves, such as in the spine, ribs, and skull. They all need each other.
all three things are simultaneously necessary It makes perfect sense however the eumetazoa (and evolutionary results as cnidarian) seem to be telling us something different, since they don't need muscles and bones to move...
How about muscles and bones being evolutionary products of mesoglea? Maybe I'm being nonsensical, but, as you said, they're all related to movement...
P.S. Or at least exoskeletons could come from a type of mesoglea.
Right, well you would simply need to make that connection and find evidence for it. Currently, if you removed our skeletal system, nervous system, or muscular system, we become vegetative, comatose, or simply die. We don't have anything that resembles an exoskeleton or a mesoglea in our bodies as far as I know.
From what I've seen, those belong to a completely separate branch of evolution.
you would simply need to make that connection and find evidence for it. I really wish to have the scientific skills required for that...
We don't have anything that resembles an exoskeleton or a mesoglea in our bodies as far as I know. Well, corals are also cnidarian and they have mesogleas, yet I'm reading they have the ability to secrete calcium carbonate, which results in a kind of exoskeleton... So I guess these two are not unrelated.
So you would need to correlate these two to bony creatures, although as you said, those are very distant from us mammals, maybe cartilage could have a word on this...
I mean cartilage doesn't answer the question, it just shifts it to the same problem. I could ask what came first, muscles or cartilage, muscles or tendons, muscles or exoskeletons.
Perhaps an easier question would be how do you think jellyfish or squids could evolve a skeletal system?
@John, Perhaps an easier question would be how do you think jellyfish or squids could evolve a skeletal system?
An easier question? lol.
Power to the imagination: they're compiting with fishes for the food, so some features could make them improve their hunt... Since corals (their cousins) generate calcium to emulate an exoskeleton, maybe they could do the same... Or its oral arms could turn into muscly appendixes...
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Maybe it would be more fruitful to pose this question to an evolutionary biologist.
That's kinda what I was thinking too. Maybe this belongs in a biological forum instead of a "religious" forum.
That is, assuming it's an honest question and not just an attempt to get to "irreducible complexity".
You guys are the disciples of evolutionary biologists are you not?
I'm not, and don't remember ever claiming to be so.
My apologies, I thought you believed in evolution.
Well, no, I don't *believe* in it. However, I think it is fact based on the evidence. To be clear, to me, belief requires acceptance of something without evidence.
But that aside, I'm not an evolutionary biologist, and to my knowledge, no one who is an active poster here is one either. So if you are legitimately interested in information that would answer your OP, your best resource would be an evolutionary biologist, not a poster on some unrelated forum.
Fine, the distinction between beliefs and knowledge is blurry anyway. Most theists on this forum are not theologians, historians, or biologists. Would it be a fair assumption that no one should be posting questions here if they want legitimate answers?
Well, I suppose it depends on the question. Some questions folks are able to answer easily, some they are simply not qualified to answer. Now if you want to know what one would guess is the answer or supposes is the answer, fine. No problem. I suggested you ask an expert because it sounded to me like you wanted an expert answer.
@CyberLN
And just how would that be more fruitful. It's obvious that John wants opinions from members of the forum.
Your statement is tantamount to saying "don't ask questions here, go away."
Agreed.
As far as I can tell, he's not asking the question honestly. He's asking it to get us into a "gotcha" position.
If he REALLY wanted to know which came first, there are better places to get that answer. Although, if he wants to know this from an "atheistic" perspective, I'd tell him to go to athiestforums.org. There's a resident biologist there who could probably answer this question in great detail.
Initially, I asked out of curiosity. But I guess I asked a good question, since everyone wants me to go away lol.
You have to understand that a lot of us have been through questions like this where the person had ulterior motives, to prove something or to steer the conversation in a certain direction.
If you are just curious and genuinely asking the question, then I apologize.
That being said, you aren't asking general questions about evolution, you asking for very specific details about a very specific function.
I'd venture for most people here, the only honest answer will be "I don't know". Anyone who could answer to the detail you're looking for will likely either be an actual biologist, or at least have done a good amount of study in biology.
So I'm afraid you're probably not going to get an answer to your liking here.
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