What came first, the chicken or the egg?

SW VandeCarr

The discussion exists because chickens don't die from complications of pregnancy. Before the 20th century 1000-2000 women per 100000 live births died from complications of pregnancy. Even today it's about 14 per 100000 live births in the US. Placental viviparity is complicated and prone to many more difficulties for the mother (morbidity as well as mortality) than oviparity. In the past, pregnancy was treated almost as a disease with women being confined for months. Yes, eggs need to be watched as do the hatchlings. But the mammalian young also need to be nurtured and protected after birth for periods of a year or longer. In the case of humans, it's now officially up to 26 years under US tax law. The egg needs to be incubated and protected, but birds have developed efficient ways to accomplish this.

Of course there's nothing we can do about this except perhaps by using surrogates for those women who have the money and want to go to the beach. Nevertheless, the costs of viviparity in humans far exceed the benefits IMO. If we laid eggs, there would be easy inexpensive ways for us to protect them and keep them warm.

http://www.digitalhistory.uh.edu/his...childbirth.cfm

RabbitWho

THAT'S a chicken!?

What the heck is this then?

Allawonder

Well, from the statement, I don't see why we all seem perplexed: the chicken came first in 'What came first, the chicken or the egg?' Anyway, nice discussion so far... LOL!

Cerlid

Yeah but surely if you think about live birth over the whole animal kingdom you can come up with a few reasons why it is better than laying eggs, that was my point. Let's try thinking about why live birth favours species not why it might disadvantage one species, and as it turns out it didn't anyway. 7 billion of us, we live in more environments than any other mammalian species on every continent, and we show a remarkable evolutionary fitness, despite our need to wipe each other out on a massive scale, we're very good breeders because of live birth, because of the socialisation that brings and because of the protection that brings to our offspring.

Cherry picking humans, and humans who happen to rule the world as a species at that seems reaching a little, but if you want to discuss how bad off we are then let's do that. Whilst I agree it seems that us developing such large heads, and such wide shoulders, and walking upright may at first of seemed a massive disadvantage but all those things gave us the ability to use our hands freely, to be wise, and to develop medicine. The fact that you are even typing this on a mass communication device, just asserts every dominance the human race has gained. And that's evolution for you, it is blind, but sometimes seemingly dumb evolutionary trails lead to seemingly massive advances in a species that mean their only threat of extinction is themselves, unlike every other species on the planet who's major threat is us.

I don't genuinely see why we have been disadvantaged by live birth given a holistic view; and more importantly given the dominance of live birthing animals general I don't see why they have either as a whole. Hence I don't see the issue. Eggs don't work as well to produce diversity, unless they are internal and not laid in a fashion that means they are subject to predators etc, except in smaller ecological niches. It's evolution baby, when it works and well, and when it favours sexual reproduction and a species, then it is unquestionable that it is better, it would not exist if it was not.

tiny-tim

from http://en.wikiquote.org/wiki/Evolution …

A hen is only an egg's way of making another egg.

(Samuel Butler, in Life and Habit, 1877).

Darwin123

Not if its a shark's egg!

jojay99

Not true. Otherwise, we should all be single cell organisms.

Darwin123

Most mammal females do not have the same level of difficulty giving birth as humans. Humans are an unusual species of mammal in terms of their difficulty in giving birth.
Human babies have big skulls which can hardly fit through the pelvic opening of the mother. This is why human mothers usually have only one baby at a time. Twins are much more difficult. Triplets still more.
Modern technology helps the offspring of multiple births to survive. Before incubators and milk bottle formulas, even a premature baby had difficulty surviving. You hear a little in ancient stories about twins. You seldom hear about triplets and quadruplets.
A dog can give birth to more than five puppies at once. Often, four or more will survive. So can mice, pigs and other mammals. How often have you heard of a dog dying in childbirth? Have you ever heard of cats or pigs dying in childbirth?
Hyenas are eutharia that have very small babies. How many hyena have died in childbirth? The marsupials have very small babies. Who ever heard of a kangeroo dying in childbirth?
Laying a large egg is at least as risky as giving live birth to a small baby. Yet, the kiwi lays a large egg and the marsupials give birth to small babies.
Our evolution has not caught up with the growth of our brains. Women die in childbirth because the human brain is proportionally larger than that of other mammals.
Taking the human species out of the discussion, live birth isn't much more dangerous than egg-laying. There is as much mystery concerning why all birds lay eggs as there is concerning the fact that most mammals give birth live.
Since there is so many niches that have both egg layers and live bearers, the answer must be in the early history of both classes of animals: the birds and the mammals. Egg laying is the most common mode of operation. However, somehow it didn't work out for the common ancestor of all marsupials and eutharia. The question is why most mammals out of all the vertebrates are usually live bearers.
The answer is probably historical. There may have been an environmental factor where living bearing animals have a large advantage.
The links previous posted on live-bearing squamata seem rather suggestive. Most live bearing squamata live in cold climates. It makes sense to me that some of the early mammals may have lived in cold climates. Their warm bloodedness is consistent with that hypothesis.
While we may never know the answer, I think that it is a plausible conjecture. Some Mesozoic species of mammal living near the North or South pole may be the most recent common ancestor of all the eutharia and marsupials.
I would suggest that paleontologists start to look for Mesozoic mammal fossils in a region that used to be near the North or South pole. There are deposits of dinosaur fossils in such areas. I hope they find mammal fossils there. Paleontologists, start looking for the little fossils in these Mesozoic polar regions!

bobze

Yes, it is true. A change in species happens at the level of a population, when we have changes in allele frequencies within the population. It doesn't happen with individuals. That is a common misconception. There is no "first organism" born of a species one day.

We're not single celled organisms, because populations changed overtime. Not because a new species ever arose through one individual.

SW VandeCarr

Humans may well have more potential complications of pregnancy than other mammals, but all mammals are subject to ectopic pregnancies, infections, fetal-maternal incompatibility, especially with free breeding animals, as well as other problems. Dogs are not immune.

http://www.pethealthandcare.com/dog-...-problems.html

If you google veterinary medicine, problem pregnancies, you will find references to canine, feline, equine and bovine pregnancies. Cattle ranchers are very familiar with problem pregnancies in their herds.

Ken Natton

This of course is the heart of the point. As others have pointed out, the egg, as meant in the question, appeared some vast time period before anything even vaguely resembling a modern chicken. But the clear assumption underlying the question is that it is possible to identify the first chicken, or even the first egg. Neither assumption has any foundation whatever.

RabbitWho

I read somewhere (why can I never remember where?) that difficult childbirth is a trade we made when we started standing upright, that it changed the shape of our hips in a way that makes childbirth a pain in the hiney.

checkbox

Assuming we are talking about a 'modern' chicken and a 'modern' chicken egg, the answer would seem to be: the egg.

Rationale: two creatures both 99.999% (etc) genetically similar to modern chickens, but in different ways, mated. The result is an egg that now contains 100% 'modern' chicken DNA.

Ken Natton

Hmmm. You're still not getting it, checkbox. You are assuming that all living chickens are gentically identical. They are not. All living chickens, like all living humans, are mutants.

QuantumHop

A chicken is just an egg's way of making another egg

Jimmy Snyder

If I remember correctly from my HS health course, it was the rooster.

Pythagorean