This page forms part of an etymology course that gives an outline of the development of English. It is written in a sequence that you may want to follow. The best place to start, if you want to follow the whole course, is Etymology course, or, if you are only interested in English, Development of English. You may also arrive at any of these articles from other links. For more information about the history of English, you should of course read a good history of the language, such as Baugh (1993), Strang (1970), or Crystal (2005)
Much of the description of different languages and how they develop is based on ideas akin to those found in evolution. In particular, modern teaching of etymology relies heavily on the metaphor of the language family. This suggests, correctly, that languages grow and change. It traces relationships of ancestry and descent, which are the best explanations we have of the differences in languages. It is not a wholly successful metaphor, as languages can influence each other whether related or not; and languages of the same generation which are descended from the same parent can influence each other in ways that real brothers and sisters cannot; nor is a language born in an instant, like a human baby. But to talk of a language family is to suggest the relationships between different groups of language.
There are many families of languages, of which there are grounds to suppose that the 'Sino-Tibetan' group (containing most of the languages called 'Chinese') has more speakers than any others. The group in which students of English must be most interested in is the Indo-European super-family, which contains several families. Among these, English belongs to the West Germanic family, and has been heavily influenced by members (particularly French and, less so, Latin) of the Romance family and by the North Germanic language family. Every continent has its own language families, as indeed evolutionary theory would suggest: their isolation applies to the ways that their peoples speak, as well as to the physical developments of the different species that inhabit them. In Africa there are the 'Nilo-Saharan', the 'Khoisan' (well-known for its use of 'click' sounds in speech), the 'Niger-Congo' and the 'Afro-Asiatic' group (which includes the Semitic family usually associated with west Asia). In America, many native American language families have been distinguished, although scholars debate precisely how they should be classified. Some of the names that have been proposed are the 'Eskimo-Aleut' family, from the Arctic area; the Athabaskan from the western side of North America and the Algonquian from the eastern side; the 'Mayan' from Central America; and 'Ge-Pano-Carib' , 'Andean-Equatorial' and 'Macro-Chibchan' from South America. In Asia, there are the 'Altaic', 'Korean and 'Japanese' families, mostly towards the east; to the south, there are 'Dravidian' languages, as well as the dominant Indo-European languages, 'Hindi', 'Panjabi' (or 'Punjabi') and 'Urdu'.
Most of the information on this page has been drawn from The Cambridge Encyclopedia of Language.