Biosemiotics is the synthesis of biology and semiotics, and its main purpose is to show that semiosis is a fundamental component of life, i.e., that signs and meaning exist in all living systems. This idea started circulating in the 1960s and was proposed independently from enquires taking place at both ends of the Scala Naturae. At the molecular end it was expressed by Howard Pattee’s analysis of the genetic code, whereas at the human end it took the form of Thomas Sebeok’s investigation into the biological roots of culture. Other proposals appeared in the years that followed and gave origin to different theoretical frameworks, or different schools, of biosemiotics. They are: (1) the physical biosemiotics of Howard Pattee and its extension in Darwinian biosemiotics by Howard Pattee and by Terrence Deacon, (2) the zoosemiotics proposed by Thomas Sebeok and its extension in sign biosemiotics developed by Thomas Sebeok and by Jesper Hoffmeyer, (3) the code biosemiotics of Marcello Barbieri and (4) the hermeneutic biosemiotics of Anton Markoš. The differences that exist between the schools are a consequence of their different models of semiosis, but that is only the tip of the iceberg. In reality they go much deeper and concern the very nature of the new discipline. Is biosemiotics only a new way of looking at the known facts of biology or does it predict new facts? Does biosemiotics consist of testable hypotheses? Does it add anything to the history of life and to our understanding of evolution? These are the major issues of the young discipline, and the purpose of the present paper is to illustrate them by describing the origin and the historical development of its main schools.