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.'
Only if yo' mommy was a Carp and yo' daddy was a Flounder.
May I recommend a Good Book on the subject? The truth of the first two chapters will rid you of the unknown, as defined by your word 'probably', and set you free.
The similarities ARE the evidence. No one guaranteed you'd be convinced by it.
Don't you know? It is as proven a fact as gravity!
Lungs were developed out of necessity because of a lack of water for use with gills. The local lizard 101 was responsible for the manufacture and had they not been on strike evolution would not have taken millions of years.
Sounds like you're talking about poofism, or one of its variants like creationism.
Coulda fooled me. Looks like vestigial gills (i.e., the pharyngeal clefts), a tail-- and FINS too, fancy that!
Guess I need to read the Bible and forget what my own lyin' eyes are telling me.
-ccm
There's a difference between poofism and creationism?
So are you accusing Christ of being a deceiver or a dolt? Not very nice of you either way.
I am created in the image of God. And I'm pretty sure God's not a fish.
My old high school english teacher said man did not evolve from the ape, he evolved from the jackass!
Define "humans."
Define "suckers."
Define "straws."
Define "grasp."
Define "story."
Define "define."
And when you're finished please remember: along with the rest of the universe you are the product of nothing more than an unguided process of elemental chaos.
"Once it was apes, then aardvarks and now fish. There's no telling what else we "evolved" from."
Didnd't all democrats evolve from snakes?
They're YOUR words. Not mine.
I truly hope He forgives you.
(1) The author didn't say that human embryos have gills. He said that fish gills and human parathyroid glands both originate from the embryonic pharyngeal pouches.
(2) As for human embryos having tails:
No. Democrats evolved into snakes.
The forked-tongue fossil record proves it.
Does not apply.
No human mother could exist without first being a human infant.
No human infant could exist without having a human mother care for it for years after birth.
See the dilemna?
It's true. Scientists will never be as sure of themselves as poofists. The price of skepticism, I suppose.
Why do you try? Do you fancy yourself a cult deprogrammer?
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