The chicken or the egg causality dilemma is commonly stated as the question, "which came first: the chicken or the egg?" The dilemma stems from the observation that all chickens hatch from eggs and all chicken eggs are laid by chickens. "Chicken-and-egg" is a metaphoric adjective describing situations where it is not clear which of two events should be considered the cause and which should be considered the effect, to express a scenario of infinite regress, or to express the difficulty of sequencing actions where each seems to depend on others being done first. Plutarch posed the question as a philosophical matter in his essay "The Symposiacs", written in the 1st century CE. [1] [2]
The question represents an ancient folk paradox addressing the problem of origins and first cause. [3] Aristotle, writing in the fourth century BCE, concluded that this was an infinite sequence, with no true origin. [3] Plutarch, writing four centuries later, specifically highlighted this question as bearing on a "great and weighty problem (whether the world had a beginning)". [4] In the fifth century CE, Macrobius wrote that while the question seemed trivial, it "should be regarded as one of importance". [4]
By the end of the 16th century, the well-known question seemed to have been regarded as settled in the Christian world, based on the origin story of the Bible. In describing the creation of animals, it allows for a first chicken that did not come from an egg. However, later Enlightenment philosophers began to question this solution. [4] Carlo Dati in the mid 17th-century published an erudite satire on the subject. [5]
Although the question is typically used metaphorically, evolutionary biology provides literal answers, made possible by the Darwinian principle that species evolve over time, and thus that chickens had ancestors that were not chickens, [4] similar to a view expressed by the Greek philosopher Anaximander when addressing the paradox. [3]
If the question refers to eggs in general, the egg came first. The first amniote egg – that is, a hard-shelled egg that could be laid on land, rather than remaining in water like the eggs of fish or amphibians – appeared around 312 million years ago. [6] In contrast, chickens are domesticated descendants of red junglefowl and probably arose little more than eight thousand years ago, at most. [7]
If the question refers to chicken eggs specifically, the answer is still the egg, but the explanation is more complicated. [8] The process by which the chicken arose through the interbreeding and domestication of multiple species of wild jungle fowl is poorly understood, and the point at which this evolving organism became a chicken is a somewhat arbitrary distinction. Whatever criteria one chooses, an animal nearly identical to the modern chicken (i.e., a proto-chicken) laid a fertilized egg that had DNA making it a modern chicken due to mutations in the mother's ovum, the father's sperm, or the fertilised zygote. [9] [4] [10] [11]
It has been suggested that the actions of a protein found in modern chicken eggs may make the answer different. [10] [11] In the uterus, chickens produce ovocleidin-17 (OC-17), which causes the formation of the thickened calcium carbonate shell around their eggs. Because OC-17 is expressed by the hen and not the egg, the bird in which the protein first arose, though having hatched from a non-reinforced egg, would then have laid the first egg having such a reinforced shell: the chicken would have preceded this first 'modern' chicken egg. [10] [11] However, the presence of OC-17 or a homolog in other species, such as turkeys [12] and finches [13] suggests that such eggshell-reinforcing proteins are common to all birds, [14] and thus long predate the first chickens.
Poultry are domesticated birds kept by humans for the purpose of harvesting animal products such as meat, eggs or feathers. The practice of raising poultry is known as poultry farming. These birds are most typically members of the superorder Galloanserae (fowl), especially the order Galliformes. The term also includes waterfowls of the family Anatidae but does not include wild birds hunted for food known as game or quarry.
The chicken is a large and round short-winged bird, domesticated from the red junglefowl of Southeast Asia around 8,000 years ago. Most chickens are raised for food, providing meat and eggs; others are kept as pets or for cockfighting.
An egg is an organic vessel grown by an animal to carry a possibly fertilized egg cell and to incubate from it an embryo within the egg until the embryo has become an animal fetus that can survive on its own, at which point the animal hatches.
Peptide mass fingerprinting (PMF), also known as protein fingerprinting, is an analytical technique for protein identification in which the unknown protein of interest is first cleaved into smaller peptides, whose absolute masses can be accurately measured with a mass spectrometer such as MALDI-TOF or ESI-TOF. The method was developed in 1993 by several groups independently. The peptide masses are compared to either a database containing known protein sequences or even the genome. This is achieved by using computer programs that translate the known genome of the organism into proteins, then theoretically cut the proteins into peptides, and calculate the absolute masses of the peptides from each protein. They then compare the masses of the peptides of the unknown protein to the theoretical peptide masses of each protein encoded in the genome. The results are statistically analyzed to find the best match.
In biology, the nuclear matrix is the network of fibres found throughout the inside of a cell nucleus after a specific method of chemical extraction. According to some it is somewhat analogous to the cell cytoskeleton. In contrast to the cytoskeleton, however, the nuclear matrix has been proposed to be a dynamic structure. Along with the nuclear lamina, it supposedly aids in organizing the genetic information within the cell.
An eggshell is the outer covering of a hard-shelled egg and of some forms of eggs with soft outer coats.
Dichlorodiphenyldichloroethylene (DDE) is a chemical compound formed by the loss of hydrogen chloride (dehydrohalogenation) from DDT, of which it is one of the more common breakdown products. Due to DDT's massive prevalence in society and agriculture during the mid 20th century, DDT and DDE are still widely seen in animal tissue samples. DDE is particularly dangerous because it is fat-soluble like other organochlorines; thus, it is rarely excreted from the body, and concentrations tend to increase throughout life. The major exception is the excretion of DDE in breast milk, which transfers a substantial portion of the mother's DDE burden to the young animal or child. Along with accumulation over an organism's lifetime, this stability leads to bioaccumulation in the environment, which amplifies DDE's negative effects.
Bird eggs are laid by the females and range in quantity from one to up to seventeen. Clutch size may vary latitudinally within a species. Some birds lay eggs even when the eggs have not been fertilized; it is not uncommon for pet owners to find their lone bird nesting on a clutch of infertile eggs, which are sometimes called wind-eggs.
The molluscshell is typically a calcareous exoskeleton which encloses, supports and protects the soft parts of an animal in the phylum Mollusca, which includes snails, clams, tusk shells, and several other classes. Not all shelled molluscs live in the sea; many live on the land and in freshwater.
Dinosaur eggs are the organic vessels in which a dinosaur embryo develops. When the first scientifically documented remains of non-avian dinosaurs were being described in England during the 1820s, it was presumed that dinosaurs had laid eggs because they were reptiles. In 1859, the first scientifically documented dinosaur egg fossils were discovered in France by Jean-Jacques Poech, although they were mistaken for giant bird eggs.
Humans and their hominid relatives have consumed eggs for millions of years. The most widely consumed eggs are those of fowl, especially chickens. People in Southeast Asia began harvesting chicken eggs for food by 1500 BCE. Eggs of other birds, such as ducks and ostriches, are eaten regularly but much less commonly than those of chickens. People may also eat the eggs of reptiles, amphibians, and fish. Fish eggs consumed as food are known as roe or caviar.
Darwinopterus is a genus of pterosaur, discovered in China and named after biologist Charles Darwin. Between 30 and 40 fossil specimens have been identified, all collected from the Tiaojishan Formation, which dates to the middle Jurassic period, 160.89–160.25 Ma ago. The type species, D. modularis, was described in February 2010. D. modularis was the first known pterosaur to display features of both long-tailed (rhamphorhynchoid) and short-tailed (pterodactyloid) pterosaurs, and was described as a transitional fossil between the two groups. Two additional species, D. linglongtaensis and D. robustodens, were described from the same fossil beds in December 2010 and June 2011, respectively.
Elongatoolithus is an oogenus of dinosaur eggs found in the Late Cretaceous formations of China and Mongolia. Like other elongatoolithids, they were laid by small theropods, and were cared for and incubated by their parents until hatching. They are often found in nests arranged in multiple layers of concentric rings. As its name suggests, Elongatoolithus was a highly elongated form of egg. It is historically significant for being among the first fossil eggs given a parataxonomic name.
Eggshell membrane separation is a recycling process to separate the protein-rich eggshell membrane from the eggshell.
In molecular biology, the latexin family is a family of proteins which family consists of several animal specific latexin and proteins related to latexin that belong to MEROPS proteinase inhibitor family I47, clan IH.
Eggshell membrane or shell membrane is the clear film lining eggshells, visible when one peels a boiled bird egg. Chicken eggshell membranes are used as a dietary supplement.
Egg drop syndrome '76 is a viral disease that affects birds, notably chickens, ducks, geese and swans. It is characterised by a sudden drop in production of eggs as well as its eggshell quality in apparent healthy laying birds.
Shell-less chick embryo culture is the process of growing chick embryos in vitro, without their protective egg shells, for scientific observation.
Avian metaavulavirus 2, formerly Avian paramyxovirus 2, is a species of virus belonging to the family Paramyxoviridae and genus Metaavulavirus. The virus is a negative strand RNA virus containing a monopartite genome. Avian metaavulavirus 2 is one of nine species belonging to the genus Metaavulavirus. The most common serotype of Avulavirinae is serotype 1, the cause of Newcastle disease (ND). Avian metaavulavirus 2 has been known to cause disease, specifically mild respiratory infections in domestic poultry, including turkeys and chickens, and has many economic effects on egg production and poultry industries. The virus was first isolated from a strain in Yucaipa, California in 1956. Since then, other isolates of the virus have been isolated worldwide.
Ancient proteins are complex mixtures and the term palaeoproteomics is used to characterise the study of proteomes in the past. Ancients proteins have been recovered from a wide range of archaeological materials, including bones, teeth, eggshells, leathers, parchments, ceramics, painting binders and well-preserved soft tissues like gut intestines. These preserved proteins have provided valuable information about taxonomic identification, evolution history (phylogeny), diet, health, disease, technology and social dynamics in the past.