Language family


A language family is a group of languages related through descent from a common ancestor, called the proto-language of that family. The term family is a metaphor borrowed from biology, with the tree model used in historical linguistics analogous to a family tree, or to phylogenetic trees of taxa used in evolutionary taxonomy. Linguists thus describe the daughter languages within a language family as being genetically related. The divergence of a proto-language into daughter languages typically occurs through geographical separation, with different regional dialects of the proto-language undergoing different language changes and thus becoming distinct languages over time.
One well-known example of a language family is the Romance languages, including Spanish, French, Italian, Portuguese, Romanian, Catalan, Romansh, and many others, all of which are descended from Vulgar Latin. The Romance family itself is part of the larger Indo-European family, which includes many other languages native to Europe and South Asia, all believed to have descended from a common ancestor known as Proto-Indo-European.
A language family is usually said to contain at least two languages, although language isolates — languages that are not related to any other language — are occasionally referred to as families that contain one language. Conversely, there is no upper bound to the number of languages a family can contain. Some families, such as the Austronesian languages, contain over 1,000.
Language families can be identified from characteristics shared amongst their languages. Sound changes are one of the strongest pieces of evidence that can be used to identify a genetic relationship because of their predictable and consistent nature, and through the comparative method can be used to reconstruct proto-languages. However, languages can also change through language contact, which can falsely suggest genetic relationships. For example, the Mongolic, Tungusic, and Turkic languages share many similarities that have led several scholars to believe they were related. These supposed relationships were later discovered to be derived through language contact and thus they are not related through shared ancestry. Eventually though, intense language contact with other language families, and inconsistent changes within the original language family, will obscure inherited characteristics and make it virtually impossible to deduce earlier relationships; even the oldest demonstrable language family, Afroasiatic, is far younger than language itself.

Major language families

Estimates of the number of language families in the world may vary widely. According to Ethnologue there are 7,151 living human languages across 142 different language families. Lyle Campbell identifies a total of 406 independent language families, including isolates.
Ethnologue 27 lists the following families that contain at least 1% of the 7,164 known languages in the world; while Glottolog 5.0 lists the following as the largest families, of 7,788 languages :

Language counts can vary significantly depending on what is considered merely a dialect; for example Lyle Campbell counts only 27 Otomanguean languages, although he, Ethnologue and Glottolog also disagree as to which languages belong in the family.
Neither Ethnologue nor Glottolog list the language families of sign languages. Of sign language families, the Francosign family, hosting around 70 languages, is by far the largest and most widespread.
The largest five language families in terms of number of speakers make up five-sixths of the world’s population.

Genetic relationship

Two languages have a genetic relationship, and belong to the same language family, if both are descended from a common ancestor through the process of language change, or one is descended from the other.
The term and the process of language evolution are independent of, and not reliant on, the terminology, understanding, and theories related to genetics in the biological sense, so, to avoid confusion, some linguists prefer the term genealogical relationship.
There is a remarkably similar pattern shown by the linguistic tree and the genetic tree of human ancestry
that was verified statistically. Languages interpreted in terms of the putative phylogenetic tree of human languages are transmitted to a great extent vertically as opposed to horizontally.

Establishment

In some cases, the shared derivation of a group of related languages from a common ancestor is directly attested in the historical record. For example, this is the case for the Romance language family, wherein Spanish, Italian, Portuguese, Romanian, and French are all descended from Latin, as well as for the North Germanic language family, including Danish, Swedish, Norwegian and Icelandic, which have shared descent from Ancient Norse. Latin and ancient Norse are both attested in written records, as are many intermediate stages between those ancestral languages and their modern descendants.
In other cases, genetic relationships between languages are not directly attested. For instance, the Romance languages and the North Germanic languages are also related to each other, being subfamilies of the Indo-European language family, since both Latin and Old Norse are believed to be descended from an even more ancient language, Proto-Indo-European; however, no direct evidence of Proto-Indo-European or its divergence into its descendant languages survives. In cases such as these, genetic relationships are established through use of the comparative method of linguistic analysis.
In order to test the hypothesis that two languages are related, the comparative method begins with the collection of pairs of words that are hypothesized to be cognates: i.e., words in related languages that are derived from the same word in the shared ancestral language. Pairs of words that have similar pronunciations and meanings in the two languages are often good candidates for hypothetical cognates. The researcher must rule out the possibility that the two words are similar merely due to chance, or due to one having borrowed the words from the other. Chance resemblance is ruled out by the existence of large collections of pairs of words between the two languages showing similar patterns of phonetic similarity. Once coincidental similarity and borrowing have been eliminated as possible explanations for similarities in sound and meaning of words, the remaining explanation is common origin: it is inferred that the similarities occurred due to descent from a common ancestor, and the words are actually cognates, implying the languages must be related.

Linguistic interference and borrowing

When languages are in contact with one another, either of them may influence the other through linguistic interference such as borrowing. For example, French has influenced English, Arabic has influenced Persian, German has influenced Hungarian, Sanskrit has influenced Tamil, and Chinese has influenced Japanese in this way. However, such influence does not constitute a genetic relationship between the languages concerned. Linguistic interference can occur between languages that are genetically closely related, between languages that are distantly related and between languages that have no genetic relationship.

Complications

Some exceptions to the simple genetic relationship model of languages include language isolates and mixed, pidgin and creole languages.
Mixed languages, pidgins and creole languages constitute special genetic types of languages. They do not descend linearly or directly from a single language and have no single ancestor.
Isolates are languages that cannot be proven to be genealogically related to any other modern language. As a corollary, every language isolate also forms its own language family—a genetic family which happens to consist of just one language. One often cited example is Basque, which forms a language family on its own; but there are many other examples outside Europe. On the global scale, the site Glottolog counts a total of 423 language families in the world, including 184 isolates.

Monogenesis

One controversial theory concerning the genetic relationships among languages is monogenesis, the idea that all known languages, with the exceptions of creoles, pidgins and sign languages, are descendant from a single ancestral language. If that is true, it would mean all languages are genetically related, but in many cases, the relationships may be too remote to be detectable. Alternative explanations for some basic observed commonalities between languages include developmental theories, related to the biological development of the capacity for language as the child grows from newborn.

Structure of a family

A language family is a monophyletic unit; all its members derive from a common ancestor, and all descendants of that ancestor are included in the family. Thus, the term family is analogous to the biological term clade. Language families can be divided into smaller phylogenetic units, sometimes referred to as "branches" or "subfamilies" of the family; for instance, the Germanic languages are a subfamily of the Indo-European family. Subfamilies share a more recent common ancestor than the common ancestor of the larger family; Proto-Germanic, the common ancestor of the Germanic subfamily, was itself a descendant of Proto-Indo-European, the common ancestor of the Indo-European family. Within a large family, subfamilies can be identified through "shared innovations": members of a subfamily will share features that represent retentions from their more recent common ancestor, but were not present in the overall proto-language of the larger family.
Some taxonomists restrict the term family to a certain level, but there is little consensus on how to do so. Those who affix such labels also subdivide branches into groups, and groups into complexes. A top-level family is often called a phylum or stock. The closer the branches are to each other, the more closely the languages will be related. This means if a branch of a proto-language is four branches down and there is also a sister language to that fourth branch, then the two sister languages are more closely related to each other than to that common ancestral proto-language.
The term macrofamily or superfamily is sometimes applied to proposed groupings of language families whose status as phylogenetic units is generally considered to be unsubstantiated by accepted historical linguistic methods.