Abstract
Symbiogenesis is a form of horizontal evolution that occurred 2 billion years ago, with the evolution of eukaryotic cells. It will be argued that, just as we can develop universal selection theories based upon a general account of natural selection, we can also develop a universal symbiogenetic principle that can serve as a general framework to study the origin and evolution of language. (1) Horizontal evolution will be compared with and distinguished from vertical evolution. (2) Different examples of intra- and interspecific horizontal evolution will be given to show that horizontal evolution is quantitatively and qualitatively the most commonly occurring form of evolution throughout the history of life. (3) Finally, three examples are given of how a universal symbiogenesis principle can be implemented in the study of language origins and evolution, more specifically within: (a) the study of language variation, (b) language genes and (c) conceptual blending.