For a long time, twins have been considered as a sign from God, which was marking a discontinuity in the natural order of things.
Differently from many other species, humans reproduce themselves in a single “event”: the embryo, during gestation, develops into a fetus within the uterus. The evolution of this process is related to both maternal and fetal factors and associated with the human morphogenetic complexity and also with the uterus stretching due to human erect posture.
Some ethnic groups typically show a higher frequency of twins than the average. Above all, many African populations can be mentioned as notable in twins’ birth rates, for instance the Yoruba communities (mostly present in Nigeria). Even in these areas, twins birth have been considered as a curse or a divine punishment, probably also because of higher mortality and defect rates of twins with respect to individual births. Moreover, twin births were often seen as a sign of resemblance to animals, for which multiple births is a very frequent and typical phenomenon. Sometimes, due to this feeling of malsanity and sexual promiscuity, these populations have committed infanticide in order to redeem themselves somehow.
Mediterranean civilizations have been characterized by a significant number of myths about twins, whose birth has always been seen as an exceptional and extraordinary event. Castore and Pollux, the Dioscuri, were born twins together with Elena and Clitennestra from Zeus and Leda. The “Dioscuri” twins, whose name comes from the names “Zeus” and Kouros”, sons of God, have been depicted and venerated by the Greek and Italic civilizations, as shown by numerous temples and sculptures. They were told to be heroes and warriors, main characters of epic tales like those of the Argonauts and of Hercules and his labors. The myth stresses their dizygotic origin, since just one of them was considered as son of Zeus. Leda never disclosed to Zeus which one of the two brothers was his son and which one son of Tindaro, king of Sparta and Leda’s legitimate husband. When Castore died during an epic fight, Pollux asked his father for the possibility of leaving his condition of immortality to remain closed to the brother. Zeus, touched by this request, satisfied his wish and decided to host both twins partly at the Olympus and partly at the Inferi. Furthermore, he gave origin to a constellation in which Castore and Pollux could shine forevermore. Actually, on the Earth, these twins have gathered a significant amount of notoriety and fame, as testified by the great number of valuable sculptures and pictures depicting them. On the “Monte Cavallo” in Rome, in the nowadays celebrated “Piazza del Quirinale”, two important Statues of the Dioscuri twins dominate the center of the Square. Such statues were copied by an ancient Greek bronze, which has been lost. They had been placed for centuries at the entrance of the Terme di Costantino, and in the sixteenth century were moved to their current place by Pope Sisto V. They have become one of the most important emblem of the “eternal” city, almost as important as the “Lupa Capitolina” feeding Romolo e Remo. But just a few people are aware that the latter twins (Romolo e Remo) were added by Andrea del Pollaiolo in the fifteenth century to the original statue of the “Lupa”, which dates back to the fourth or third century B.C. The foundation of Siena is linked to the myth of Romolo and Remo: The Museo Della Scala contains a statue of Silvia with the twins, made by Iacopo della Quercia.
Other Statues of the Dioscuri twins can be found also on the Campidoglio and in many other locations of the ancient “Magna Grecia” colonies, as for instance Sicilia and Calabria. Even the twins feeded in the statue coming from Megara Hyblea, displayed at the Orsi Musem of Siracusa, might be recognized as the Dioscuri twins. This sculpture nicely depicts the twins while being feeded contemporaneously (following the position called “kourotrophos”), in a modern fashion. Nevertheless, the Dioscuri myth has survived to the end of the Greek and roman Civilizations. Leonardo Da Vinci depicted Leda with the swan, representing Zeus, and the sons, perfectly catching both the sensuality and the maternal affection. It is worth mentioning that during the “Rinascimento” twins birth was thought as consequence of a sort of excess of male semen, and hence in line with sexual promiscuity. Twins were often considered sons of different fathers, following a hypothesis made first by Aristotele in one of his book discussing natural phenomena. They have also been considered as symbol of the assisted reproductive technologies.
Also Giacobbe and Esaù were twin brothers. The Bible describes them to have been in conflict within the uterus and upon birth. Esaù upon birth is described as “rubizzo” and hairy. Some people saw in this description a clear knowledge of the process concerning the twin–twin transfusion syndrome in which we may find discordance for growth and hemoglobin levels. One twin in these cases is the donor and shows anemia while the other is the recipient and shows policytemia, on the basis of pathologic interchanges of blood flow during a twin pregnancy with anastomosis between their vascular systems.
Twins were also Cosma e Damiano, medical doctors consecrated as saints by the Catholic Church, sharing the patronage of medicine. They are often figured while offering together their cure to suffering patients.
Declaration of Interest
The authors report no conflicts of interest. The authors alone are responsible for the content and writing of this article.