Evolving the Musculoskeletal System

Found this over at NeuroDojo: The beginnings of bone, here's a very relevant excerpt pertaining to why what ICdesign is doing is so much easier than what we are doing: I think we could dig out some good information about the current state of knowledge about the origin and evolution of bones, but it would take some effort. Someone in the last day or so posted a few pictures of creatures with more primitive bones than mammals, but it would probably be helpful if we could find examples of extant creatures with just a simple cartilaginous hard part or two. There's the single-celled diatoms (a type of algae) whose cell walls are made of silica.--Percy

If someone has access This paper on the Evolution of Bone might be interesting.

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Anyone so limited that they can only spell a word one way is severely handicapped!

Found a couple articles at Wikipedia about the earliest creatures with skeletons of some sort. Here's a brief excerpt about the Namacalathus, an Ediacaran fossil: This excerpt is from the Wikipedia article on Cloudinid: So the earliest examples of skeletons in the fossil record were very, very simple, but we know very little about these organisms.--PercyEdited by Percy, : Increase image margins.Edited by Percy, : Grammar.

It also appears that bones and skeletons may have been a later development, that calcium based hard surfaces may have first developed externally with cartilage taking the place of bones internally.

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Anyone so limited that they can only spell a word one way is severely handicapped!

The earliest chordates had no bones, such as Haikouella:Haikouella - WikipediaConnective tissue is all that is needed. No bones.In modern vertebrates like us we start with the same non-calciferous notochord as an embryo that later develops into the bony vertebral column.

I guess I wasn't very clear. I was assuming that my remarks would be read in the context of IC's argument, which is that if skeletons evolved, then every species with a skeleton should contain individuals who have less-evolved skeletons. Remember? He keeps asking why, if the human skeleton evolved piece by piece over millions of years, why we don't see humans with piecemeal skeletons.And the answer is because they've already evolved skeletons; every human being inherits the genes for a fully-evolved skeleton from their parents. No human being has to evolve their own skeleton, they already have a fully-evolved one that they inherited.ICDesign has this notion that evolution is a kind of slow change that happens in individuals, where a fish grows legs and lungs and takes a step onto land. Of course, he looks around and doesn't see any of this happening at all, so naturally he doesn't believe in "evolution." He sees individuals growing into static adult forms and then not changing at all.We keep trying to tell him that evolution is something that happens to populations, not to individuals, but ICDesign believes that learning things is not a good way to understand things, he believes that knowing the least about a scientific field puts you in the best position to assess its merit. So, naturally, we will be unable to convince him that evolution is not a slow change that happens to individuals, it's a slow change that happens to populations of individuals as a result of how individuals are born different from each other.ICDesign is determined to be the person who knows the least about biology in these conversations because he believes that's the best way to judge conclusions in the field of biology. Of course, somehow I doubt he goes to doctors who have yet to attend medical school, or has his car maintenance done by people who have never in their lives seen automobiles. For some reason it's only science where ICDesign believes that the best way to know what's true is to know nothing at all.

Greetings ICDesign,It is all too common for people to confuse the two meanings of the word "theory".In popular terms, "theory" means a guess, or speculation. Thus the common phrase "just a theory" meaning "just speculation", "just an untested idea", merely a claim that might be true.But,
in scientific terms, there is another, different, meaning to the word "theory" - it means an EXPLANATION. Theories EXPLAIN factsTheories explain the facts we observe :Gravity is a fact, we observe its effects.
Gravitational Theory describes how gravity works.Electricity is a fact, we use it everyday.
Electromagnetic Theory explains the details of how it operates.Germs are a fact.
Germ Theory explains how they cause disease.Evolution is a fact, it is observed.
The Theory of Evolution explains how it works. the ToE is an EXPLANATION, NOT speculationThe Theory of Evolution is NOT "speculation about evolution" - that is NOT what the phrase means at all.Rather -
the Theory of Evolution is the EXPLANATION for how evolution works, it models the behaviour of the FACTS of evolution, and allows predictions to be made.Just as Electromagnetic Theory is the explanation or model of how electricity works.
Would one say "electricity is just a theory" ?
Of course not.And Gravitational Theory is the explanation or model of how gravity works.
Would one say "gravity is just a theory" ?
Of course not.And Germ Theory is the explanation or model of how germs cause disease.
Would one say "germs are just a theory" ?
Of course not.Yet
some people say
"evolution is (just) a theory"as if it means
"evolution is merely untested speculation" (false)when it really only means
"evolution is an explanation, or model" (true)Claiming "evolution is just a theory" indicates lack of understanding of the word, and how science operates, and that the ToE is an explanation for observed facts. EVOLUTION = FACT & THEORYEvolution is a FACT.
We observe evolution.
And,
the Theory of Evolution is the EXPLANATION, or model, for the observed facts of evolution.KapyongEdited by Kapyong, : No reason given.Edited by Kapyong, : Minor adds.

crash,oh. i see. i was having some difficulty making sense of what the heck he even meant.

Don't worry about it; I should have been more clear. And I've had some ex parte conversations with him already.

I think the consensus is that sharks are descended from bony fish.

I think the term bony fish might be a bit confusing here. Do you mean teleostomi, the actual group known as bony fish? Or do you mean fish which had some bony structures like placoderms or agnathans?If you are saying that chondricthyes, including sharks, evolved from teleosts then that is pretty contrary to what I understood to be the case.TTFN,WK

I'm with Wounded King, sharks are not descended from teleosts, which is what I'd understand bony fish to mean.

And this is the trouble with Creationists: you don't know your biology.Pick up any decent textbook on the diverse biology and read it. You'll soon discover that there are animals living today that prove your argument completely wrong. There are animals in which the organs are simply suspended in fluid. Animals which have a sort of circulation system with no heart in which the fluid is moved simply by the motions of the animal. Animals with a primitive sort of heart - really nothing more than a bit of muscle that keeps the fluid moving. Animals with the separated lung/body circulation you see in humans, but an undivided heart so that the oxygenated and deoxygenataed bloods mix as it pumps, semi-divided hearts that improve the separation of the two and then hearts like ours which fully divide the two.If you took the time to study even a little bit of biology you'd know how absurd your claims that such things couldn't exist and wouldn't work really are.

I just mean fish which have bones where sharks have cartilage.

No, I'm afraid not. The fish that have bones where the sharks have cartilage are all teleosts, it is generally accepted that elasmobranches (inc. Sharks) did not evolved from the teleost fish.