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.'
And yet, there was a time with no humans, and a later time with humans. How do you explain the interval? Are you suggesting they just poofed into existence ala "I Dream of Jeannie"?
Wow. Don't know what the melons are shaped like 'round your place, but it doesn't seem to bode well for continuation of your lineage.....
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)
Odd that the deer's neck didn't evolve to not fit the lion's mouth.
"I established the opposite view, that this history of the embryo (ontogeny) must be completed by a second, equally valuable, and closely connected branch of thought - the history of race (phylogeny). Both of these branches of evolutionary science, are, in my opinion, in the closest causal connection; this arises from the reciprocal action of the laws of heredity and adaptation... 'ontogenesis is a brief and rapid recapitulation of phylogenesis, determined by the physiological functions of heredity (generation) and adaptation (maintenance).'"
Haeckel, E. 1899. Riddle of the Universe at the Close of the Nineteenth Century.
The gill hypothesis tends to uphold Haeckel. For years scientists and their critics have denied that it is true. However, the creationists are overly critical of Haeckel and do not understand the nuance we see in developing embryos, that does present some evidence for evolution.
Haeckel was a great scientist and a genius.
Me too. I just do it for recreation. Finding otherwise intelligent people expouting poofism is just too comical to waste.
psst, that's ontogeny
I have been preaching this for many years now.
I have been working from the Hebrew in Genesis 1 for 20 years and I think much of it comports quite well with modern science, considering the culture of several thousand years ago and the restrictions of a non-technical language.
If you don't find evolution convincing, it may not be Christ that lit your bulb. It may be flames from a different place. ;-)
Just goes to show how great God is. He created reusable code before man created the computer.
Kinda makes you wonder how god-less evolutionists hold on to their fairy tale.
Merry Christmas!
"There is no proof of evolution as a matter of fact all the proof is against evolution"
Oh really? Please give us your "proof" against evolution.
You will get the Nobel prize for science.
It's called a branchial cleft cyst. The docs use the word "gill" because it's descriptive to lay people since the clefts resemble gills in the embryo. As it turns out, both fish gills AND human parathyroid glands develop from these clefts.
"Branchial pouches" is synonymous with "pharyngeal pouches" which is the term used in this article. "Branchial" = "Of, relating to, or resembling the gills of a fish, their homologous embryonic structures, or the derivatives of their homologous parts in higher animals breathing" (AHED).
"I am created in the image of God. And I'm pretty sure God's not a fish."
The image reference refers to your Spirit.
I don't think you should go around insulting God's fish.
Evolution is a fact. The Theory of Evolution explains that fact. We are still working on the various processes and collecting data to add to the mountains of data substantiating evolution is a fact.
We will never completely understand it, because God created evolution as His method of creating different life forms. He will not allow us to learn everything.
Poofism is the broader denial of the fact of space-time continuity. The fallacy is also commonly used in the abortion debate where some people claim there is a magical POOF, a precise instant, at which the beginning of a human individual can be proclaimed.
When you put things into terms of individuals, you will never understand evolution. Evolution works in terms of populations of breeding or otherwise reproducing individuals.
You are asking the chicken egg question.
When you look at comparative anatomy from single cells to man, you can follow the developments. Remember, we still have single cells and that things don't necessarily disappear. There is no direction to evolution from simple to complex as my first sentence in this paragraph may suggest.
Evolution is an elegant Theory. To understand it, it takes systemic thinking and open minded powers of observation. This is how Darwin came to it.
Thank you, but save some of that hope for yourself. You are the one accusing Him of either believing or professing absurdities.
Or, maybe it's someone else you've been hearing. I've never heard Christ tell me such nonsense.
In 1890 Ivy Leaguers were a lot more conservative than you are. lol
You're just jealous.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.