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.'
Or perhaps the parathyroid gland was put into humans in order to mislead scientists and mankind as a whole by...Satan! ;-)
\churchlady:off
Just goes to show how great God is. He created reusable code before man created the computer.
Interesting thought, and it makes a great deal of sense, and I'm wondering what thoughts there might be on the development of lungs.
Man this article makes me thirsty.
Interesting take.
I knew a girl in high school who claimed she was born with gills. She did smell kinda fishy.
Evil utionists came from green slime and have not formed brains yet!
Parathyroid glands come from gills, which is why they aren't next to your kidneys Ping!
Will one day our brains evolve into something useful in a higher creature?
Yep. Was watching a nature show the other day about mountain lions and the moderator said that "the mountain lion's mouth evolved to be a perfect fit for a deer's neck". This explains all the fossils of the extinct small-mouthed mountain lion, and the extinct large mouth mountain lion.(/sarcasm off)
You are going to take a lot of hits from creationists for this one. LOL
Haeckel is one of their boogey men.
B. S. God created me. How you got here is your problem.
ha ha ha good one.
How about maybe the cucumber plant family??
Well, we must swim before we walk.....OK, who said "you drink like a fish?"....it must be my glands...yes, that's it!!!
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