[Hadrian (OP)]

Can anyone give an answer to this?

What you do speaks so loudly that I cannot hear what you say.

[another_someone]

Easy question, the egg.

Eggs were around long before the first chicken arrived.  Ofcourse, they were not chicken eggs, but they were eggs.

George

[Hadrian (OP)]

Yea i get that. But where do eggs fit into the scheme things reguarding birth etc.

What you do speaks so loudly that I cannot hear what you say.

[neilep]

When we go shopping, we buy eggs first, then chicken. QED


In fact there is argument that the egg preceded the chicken/bird by 140 million years but i will have to get permission first before posting it here.

[daveshorts]

What do you mean by "the scheme things reguarding birth etc."?

A chicken egg is fertilised while it is still in the hen, it is finished, layed, and the foetus will develop inside if the temerature is kept right etc. Eventually it hatches...

[another_someone]

quote:Originally posted by Hadrian

Yea i get that. But where do eggs fit into the scheme things reguarding birth etc.

All animals start as eggs, just some eggs mature inside the body (as is true of placental bodies), whereas other eggs mature outside of the body.

An egg is to an animal what a seed is to a plant.

George

[Hadrian (OP)]

Where did the hard shell come from and when did it first appear?

What you do speaks so loudly that I cannot hear what you say.

[another_someone]

quote:Originally posted by Hadrian

Where did the hard shell come from and when did it first appear?

Not all eggs have a hard shell.  Birds eggs have hard shells, but as far as I know, reptile shells eggs have a leathery cover, not a hard mineral covering.

http://en.wikipedia.org/wiki/Dinosauria

quote:
Modern birds are considered to be the direct descendants of theropod dinosaurs.

What kind of eggs theropods laid I cannot say.

George

[ukmicky]

quote:Where did the hard shell come from and when did it first appear?

Hadrian

An egg with a shell probably started off millions of years ago as nothing more than an egg which the host’s body rejected but couldn’t eject or absorb and so it encased it in calcite (Calcium Carbonate).
 
Explanation.
Some life forms on earth which includes us humans have a natural process which entombs objects in calcite (Calcium Carbonate) which reside in the womb if the host’s body deems them to be foreign and cant eject them as a way to isolate it from the host body to prevent infection, sepsis etc.

Birds eggs are just eggs entombed with a shell of Calcium Carbonate so an egg with a shell could be originally just a egg that had been rejected but through a flaw of evolution an ancestor of birds was born with a way to naturally eject a rejected calcite covered egg ,which through luck happened to be a good evolutionary flaw and so the feature was adopted in all future generations as a way to incubate the young due to the natural protection a shell gave which then started a new evolutionary branch of creatures which finally ended up with birds.

PS I’m tired so excuse any typos


Michael

[another_someone]

Thinking a little about this, it occurred to me that the development of mineral shells on eggs must have developed alongside the development of the beak, because without the sharp beak, it would have been difficult to break through the hard shell, but with the beak, it must be more difficult to break out of a soft coated egg.

George

[neilep]

quote:Originally posted by Hadrian

Can anyone give an answer to this?

What you do speaks so loudly that I cannot hear what you say.

These are not my words but I thought them apt to the original question:



-----------------------------------------

Fish lay eggs in the water. Those eggs are rather simple and water permeable with no hard casing. Amphibians developed from fish, and ventured onto the land. They could not lay hard shelled eggs but soft, fishlike eggs that would dry out on land. So they returned to the water to lay eggs.

A tetrapod from Cheese Bay offers some confirmation for a 30-year-old theory about how amniotes arose. "As soon as I saw the specimen of Casineria, I was terribly excited because here was a small form," says palaeontologist Robert L. Carroll of McGill University in Montreal. In 1970, Carroll proposed that amniotes evolved from a line of miniature amphibians, much smaller than brutes like Acanthostega.

http://www.sciencenews.org/sn_arc99/5_22_99/bob1.htm

Unlike many amphibians, most plethodontid salamanders lay their eggs on land and do not pass through a larval stage. Instead, the embryonic salamanders develop directly into an adult body form. At the heart of Carroll's theory lies the amniote egg, which has a series of membranes not present in the simpler eggs of frogs and salamanders.

The oldest amniotes currently known date from the Middle Pennsylvanian locality known as Joggins, in Nova Scotia (Carroll, 1964). The relationships of these fossils indicate that amniotes first diverged into two lines, one line (Synapsida) that culminated in living mammals, and another line (Sauropsida) that embraces all the living reptiles (including birds).

One Joggins fossil, the "protorothyridid" Hylonomus, appears to be a very early member of the line leading to Sauria (Crown-clade diapsids), the clade encompassing all living diapsids. This suggests that the more inclusive clade of which turtles (Testudines) are part (Anapsida) in most morphological phylogenies had diverged as well, even though its current record extends back only to the Lower Permian (Laurin & Reisz, 1995).

http://tolweb.org/tree?group=Amniota..._Vertebrat es

Early amniotes developed a calcified shell on the outer membrane of the egg. Their survival was better than those with soft shell eggs and vastly superior to the water permeable eggs of amphibians. So the first hard shell eggs (typical of chicken eggs) were in the Middle Carboniferous Period about 310 million to 301 million years ago. The reptilian egg was from the lower Permian, 290 million to 256 million years ago. We know that the reptiles who developed into Dinosaurs in the late Triassic laid hard shelled eggs. Some of these have been found and CAT scanned showing the dino embryo inside.

Birds apparently developed in the Jurassic Period of the Mesozoic from Therapod bipedal dinosaurs related to Velociraptors. That would have been sometime between 178-160 million years ago. A Jurassic Duck similar to modern ducks has been found in Late Jurassic deposits. We don't know exactly when chickens evolved but it is likely that it came about the same time as ducks and other birds of the Jurassic and early Cretaceous.

So hard shelled eggs date back to 310 million years ago, but birds did not evolve from raptor dinosaurs until about 170-160 million years ago.

Conclusion the Egg came before the Chicken, by 140 million years or so.
-------------------------------------

Thank you to  ' Amergin '...

As I said, these are not my words and so I am unable to respond directly to comments aimed at statements within it. I just thought it relevant to the question

Men are the same as women, just inside out !

[ukmicky]

quote:Originally posted by another_someone

Thinking a little about this, it occurred to me that the development of mineral shells on eggs must have developed alongside the development of the beak, because without the sharp beak, it would have been difficult to break through the hard shell, but with the beak, it must be more difficult to break out of a soft coated egg.

George

Possible, its also possible that the shell started off very thin or the parents of the chick broke it through external measure's when they heard the chick making noise from within. (don't crocodile's sometimes help there young escape from their shells )
Its also possible that the beak was a lucky addition which came along before the egg shell or maybe it took many evolutionary changes before a chick in an egg born in a shell survived and on till that time all the babies which survived were born fully formed.

GEORGE Sorry i nearly edited yours rather than quote from it.



Michael

[neilep]

quote:Originally posted by ukmicky
GEORGE Sorry i nearly edited yours rather than quote from it.



Michael

It's horrible when you think you've done that isn't it ?

Men are the same as women, just inside out !

[ukmicky]

i was looking for my reply which i just posted and couldnt find it, i thought i was going mad until i scrolled up and found it added on to georges post. i had to do a quick un-edit[]and repost

Michael

[neilep]

quote:Originally posted by ukmicky

i was looking for my reply which i just posted and couldnt find it, i thought i was going mad until i scrolled up and found it added on to georges post. i had to do a quick un-edit[]and repost

Michael

Michael, I think it's high time we revealed that we are in fact another_someone ourselves !

In fact, it's just us two on the whole site ! []




Take it to the extreme and a forum based website could be a schizophrenics Paradise !!.......or Bedlam !

Men are the same as women, just inside out !

[ukmicky]

lol


Michael

[Andrew K Fletcher]

The answer is neither

"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"

[ukmicky]

quote:Originally posted by Andrew K Fletcher

The answer is neither

"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"

elaborate

Michael

[Andrew K Fletcher]

Long before an egg develops there has to be primary circulation. This applies to everything alive, so long before an egg or a chicken could begin the process of existing, circulation come first. Circulation is what breathes life into inanimate substances by providing the animation, so it is only right to state that a non-living physical force breathes life into all living things. And wherever the egg or the chicken originates from, it must have been conceived from the same physical force. For to have no circulation, life cannot exist and without life, we have no egg or chicken!

"The explanation requiring the fewest assumptions is most likely to be correct."
K.I.S. "Keep it simple!"

[Ophiolite]

Amoeba experience primary circulation?

Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.