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.'
"These Bible-haters get sillier and sillier every day!!"
Did you ever consider that saying God individually designed man with all the mistakes like the missing vitamin C gene all apes (like man) have and our eyes designed backward, might be the silliest thing ever? Or that the Earth is only 6000 years old because some silly priest miscounted?
Do you think God likes silly people?
"Bird mothers protect their young fiercely and even protect their eggs a lot more firecely that some Liberal human mothers protect their unborn."
It would seem the one thing liberals and creationists have in common is a reluctance to believe in evolution.
"Perhaps because we don't understand, we infer nonsense or lack of function. Imagine how dumb we really are? The Lord probably laughs all the time at our naivete. "
One true statement from a creationist. We are making some progress, except we have not come to a consensus on which side of the debate is dumb and naive.
It looks like God may have created you in His image by creating the first "amoeba" and letting evolution happen.
Did I tell you that Creation is not contained in the Theory of Evolution?
And there you have it.
Funny what passes as science these days.
I think some of them already have.
Happy Christmas, Aquinas!
Same to you!
"Point to ponder. Why is it that an "evolutionary change" happens over a small period of time and never reoccurs?
Why have there been no new ape men over the last several thousand years. Why no new fish becoming land dwellers? Why no lizards becoming birds?
On a slightly more humorous note: Did the first man have sex with a "monkey"? "
OH! He was being serious about the first questions!!! LOL
How do you define "Darwinism"?
I always wondered why it smelled like fish.
Suppose you have a haystack... and you take some hay away. Do you still have a haystack?
How much hay can you take away before it's not a "haystack" anymore? The distinction may be arbitrary, or it may be discrete. Same with "first man"... was it a single genetic difference that puts someone into that category? Is it a line that you draw and say, "this isn't much like modern man, but it's what we will consider 'man'"?
I must remember to add G.K. Chesterton to my "dinner party list"... Jesus of Nazareth, Thomas Jefferson, etc...
Easy, the scientific method does not apply to evolution.
There are many scientific methods and most of them are used to substantiate the Theory of biological evolution. In all cases peer review is used, which is probably the "method" you think means nothing.
Fish are in the path of common descent from unicellular organisms to man. We had a common ancestor, but probably split off from each other millions of years ago.
Many people you know look like fish, many smell like fish and some are almost as smart as fish. I wouldn't put down fish too much, if I were you. lol
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