He obtained his degree in Florence, where among his teachers were the Hellenist Ettore Bignone, the philologist Giorgio Pasquali and the semitists Giuseppe Furlani, Giacomo Devoto and Bruno Migliorini.
At the beginning of his career he taught Greek and Latin in a High School. In 1950 he was appointed Supervisor of Bibliography for the Veneto and in 1955 for Tuscany. He taught some lessons of Medieval Latin at the University of Florence in a School of Latin palaeography. Afterwards he was director of the Biblioteca Laurenziana and then of the Biblioteca Nazionale Centrale of Florence. In 1967 he was honoured with the gold medal for culture merits. He was a honorary member of the Accademia Etrusca. He was also a member of the Oriental Institute of Chicago.
Semerano rejected the Indoeuropean theory - taken for granted by mainstream historical linguistics. He highlighted the fact that Indoeuropean is only a constructed language, with no written records. Through comparison of a huge amount of words without convincing etymology in European languages, he supposes that these originated in Mesopotamia, from the Akkadic and Sumerian languages. According to his supporters, Semerano's works have helped better understand the story of all European languages, not only the ancient and classic ones like Greek, Latin and Etruscan, but also all other languages and dialects, both modern and ancient, in Italy and Europe.
Among the various important scholars who agree with Semerano's thesis there are: Umberto Galimberti (philosopher), Massimo Cacciari (philosopher), Franco Cardini (historian of the Middle Ages), Luciano Canfora (philologist), Emanuele Severino (philosopher), Elémire Zolla (philosopher).. With the partial exception of Canfora, there are no linguists among them, .
The origins of the European culture (not yet translated into English) has as subtitle Rivelazioni della linguistica storica (Revelations of historic linguistics - Leo Olschki, Florence 1984-1994). It is divided into 4 volumes, two of which are on etymology: one on Greek and one on Latin and modern entries. The other two volumes treat thousands of ancient and modern words of European languages, that should be related to the age-old Semitic languages, like Hebrew, Arabic, Sanskrit, Chinese and many more African languages. Several pages are dedicated to Etruscan.
The book starts by assuming an old cultural protohistoric unity of Europe and the Middle East, on the basis of a Mesopotamic derivation of many geographic and ethnic terms. The original meaning of the name of many cities, people, rivers, characters, belongings, typical verbs of thought and hand activities are also usually included in a generic Mediterranean substrate that gathers all that cannot be categorized in the Indoeuropean linguistic framework (Continental). The author suggests that Akkadic, the language with the oldest and widest written records, should be rather used as an alternative reference framework, since it also belongs to the family of Semitic languages and has the oldest evidence of Sumerian substrate, like the tens of thousands of tablets written in cuneiform, discovered in the archives of the old city of Ebla in Syria (Assyria) and dug out by the archaeologists during an Italian mission in 1968.
According to the author this linguistic framework proves the influence that Mesopotamia had on European civilizations, radiated along the Continental path of the Danube and along the coasts of the Mediterranean Sea, from Africa to Ireland. along the old trade roads of amber, tin and iron.
The work (The endlessness: a millenary misunderstanding), with the subtitle of Le antiche civiltà del Vicino Oriente e le origini del pensiero greco (The oldest civilizations of the Middle East and the origins of the Greek thought), (edited by Bruno Mondadori, 2001, collana "Sintesi" ISBN 8842497622), aims to revise all languages as entities originating from a common Akkadic and Sumerian matrix. This allows the author to reinterpret radically the entire environment of Archaic and Classic Greece, no longer regarded as a miraculous island of rationality, but as a part of a unique community including Mesopotamia, Anatolia and Egypt.
The theory of the volume is based on a new interpretation of the term Ápeiron, central in Anaximander's philosophy. Anaximander defines the element from which all things originate with the Greek term àpeiron, commonly held to be formed from a(alpha privative, "without") and péras ("determination", "limit"), and thus translated as "endless", "unlimited". According to Semerano, though, since the word péras has a short e, whereas àpeiron has a diphthong ei that reads as a long closed "e", the diphthong cannot be produced by the short e of péras.
Semerano derives it from a collision of the Semitic term 'apar, the biblical 'afar and with the Akkadic eperu, all meaning "earth". The notorious fragment of Anaximander, in which we read that all things originate and come back to the All'àpeiron would not be referred to a philosophical conception of endlessness, but to a concept of "belonging to the earth" that we can find in a previous sapiential tradition of Asian origin exemplified in the Bible: "dust you are and to dust you will return".
On the basis of this interpretation, Semerano reviews the whole development of previous sophistic philosophy with an anti-idealistic and anti-metaphysic principle, reconsidering the differences and similarities between ancient thinkers and ascribing most of them to corpuscular physics, that brings together Anaximander, Thales and Democritus.
Semerano's theories are strongly rejected by most linguists.
Semerano's objections to the Indoeuropean language theory are essentially objections to the theory as propounded by early nineteenth century German linguists. He does not consider subsequent modifications (for instance, the so-called wave model, in German Wellentheorie), that could correct and refine the first hypotheses. Such refining, it has to be said, is progressively approaching to the area where Indoeuropean should have been created (today's Anatolia) in the Mesopotamic area.
Moreover Semerano's assertions, according to which the existence of Indoeuropean would be a "??mock??", has no evidence in archeaeological finds which confirm the theory. For example, the decipherment (successfully completed and enriched through the introduction of new historical data) of Hittite tablets started from the point that it was an Indoeuropean language written in the cuneiform script.
Semerano's whole theory is based on a wide series of approaches of heterogeneous theories with no proposal of an alternative and consistent model to traditional linguistics and with no explanation and definition of linguistic laws that headed the derivation of the various languages examined by the ancient Mesopotamic languages.
In his reconstruction of the derivation of Ápeiron, Semerano appears not to know an essential element: in the Ionic dialect, unlike the Attic dialect and many other Greek dialects, the alternation between "e" (short vowel) and "ei" (diphthong), is quite common and originates from well-known linguistic dynamics. There are also synonyms of Anaximander's term in Homer, where we read of pòntos apèiritos: on Semerano's thesis, this should not be translated as "endless sea" but "earthen sea", which seems unlikely.
Another example of Semerano's paretymological approach is his suggestion for the origin of the Latin word res "thing": he ascribes it to the Akkadic rēš "head" (phrase rēšu), neglecting the fact that the final Latin -s is the ending of the nominative (therefore the root of the Latin word being re- -*reh- and not rēš). If he had started from the accusative rem he would instead have been led to the Akkadic word rēmu "belly". Semerano seems to have simply used dictionaries of various languages with little methodological scruple, often deliberately ignoring grammatical structure.