Posted on 12/21/2004 4:13:57 PM PST by beavus
The human parathyroid gland, which regulates the level of calcium in the blood, probably evolved from the gills of fish, according to researchers from King's College London.
Writing in the latest edition of Proceedings of the National Academy of Sciences, Professor Anthony Graham and Dr Masataka Okabe suggest that the gills of ancestral marine creatures, which were used to regulate calcium levels, were internalised rather than lost when land-living, four-limbed animals – the tetrapods – evolved.
Many physiological processes such as muscle contraction, blood coagulation and signalling by nerve cells, require specific levels of calcium in the body. In humans, calcium levels are regulated by the parathyroid gland, which secretes parathyroid hormone if the calcium concentration in the blood falls too low. This hormone then causes the release of calcium from bone, and increases its reuptake in the kidney, raising the calcium levels back to normal.
Fish don't have parathyroid glands. Instead they increase their internal calcium concentration by using their gills to take up calcium from the surrounding water.
'As the tetrapod parathyroid gland and the gills of fish both contribute to the regulation of extracellular calcium levels, it is reasonable to suggest that the parathyroid gland evolved from a transformation of the gills when animals made the transition from the aquatic to the terrestrial environment,' said Professor Graham.
'This interpretation would also explain why the parathyroid gland is positioned in the neck. If the gland had emerged from scratch when tetrapods evolved it could, as an endocrine organ, have been placed anywhere in the body and still exert its effect.'
The researchers supported their theory by carrying out experiments that show that the parathyroid glands of mice and chickens and the gills of zebrafish and dogfish contain many similarities.
Both gills and parathyroid gland develop from the same type of tissue in the embryo, called the pharyngeal pouch endoderm; both structures express a gene called Gcm-2, and both need this gene to develop correctly.
Furthermore, the researchers found a gene for parathyroid hormone in fish, and they discovered that this gene is expressed in the gills.
'The parathyroid gland and the gills of fish are related structures and likely share a common evolutionary history,' said Professor Graham. 'Our work will have great resonance to all those people who have seen Haeckels' pictures, which show that we all go through a fish stage in our development. This new research suggests that in fact, our gills are still sitting in our throats – disguised as our parathyroid glands.'
Okay, I'll play. My spleen is a remnant of the air bladder. Thats why I can live without if I get in a car accident.
God created reusable code. That's an excellent way to describe what seems to have happened.
Faith and reason should not conflict.
Naw. We will make one on a tiny chip of silicon. :-)
yec intrep
I understand the shorthand but I really believe it goes deeper than just the shorthand and reflects the reality of the thought process. Isn't this shorthand just too heavily relied upon because the thought that it implies is imbedded in the process?
Thank you from and x-evolutionist. I am embarassed to say I once believed this sort of nonsense. Until Christ turned the light on for me!
I don't think I'm stretching here to say that you are accusing Him of being a poofist. And poofism IS absurd.
I think the chicken/egg question is valid.
To believe their system, an evolutionist must have every bit as much faith as the creationist does in his, I think.
I'm really not here to try to convince anyone anything, but it is a fun debate.
I understand the process you are explaining.
It has nothing to do with my big picture, which is that humans would not evolve or exist without a parental oversight already in place.
I of course did no such thing. I merely characterized your description of Him.
And you post this inflamatory nonsense simply because my stated beliefs in Christ don't agree with your positions on evolution.
What's good for the goose. You have no trouble arrogating His name for your own views at the expense of others, but oh boy, if someone else does the same...
There is a word for that.
Is your whole LIFE motivated by fallacies? The facts of nature have nothing to do with what anyone, including Darwin, did or did not say.
No, the creationist's point wasn't that sensible. It really was what I said.
Deer would survive better if they evolved to fit into the lions mouth? Oooooookay.
that's old cheek and throat pouches originally holding a bubble of air
no...you are evolving into a computer and robotics...notice robots smarter that you and I at their task, needing no food or water or shelter or clothing are exploring Mars for you...this is the future of the human race
no you and apes came from a common ancestor...we all come from fish ( and earlier creatures to be fair)...want to get a surprise ? run your tongue high up your cheek ( on the inside idiot!! *hehehe*) in the direction of your cheekbone...feel the little flaps ar notches ? thise are your vestigial gills....
sorry but now you know we are from slime (-;
Post 101? I can't find the word "internalised". Did you intend to comment on the "I Dream of Jeannie" hypothesis of human development?
It's funny how evos seem to think that creatures change through some kind of will of their own. I really think that you have to read this into their thought processes.
I can't speak for what all people think, but evolutionary biologists know that isn't true. However, there is no shortage of confused lay thinking about evolutionary theory, and even the language of biologists is misleading in its causality (as you say). The closest to the truth your description reads is that creatures' behavior affects their survival, but that is not a useful trait in describing which creatures survive to reproduce, since the trait is essentially ubiquitous.
only in my dreams !!!!
( research is in biochemistry; maybe we can brew up something to help with the dreams)
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