Mermaid
Tales of mermaids are nearly universal. The first known mermaid stories appeared in Assyria, ca. 1000 BCE. Atargatis, the mother of Assyrian queen Semiramis, was a goddess who loved a mortal shepherd and in the process killed him. Ashamed, she jumped into a lake to take the form of a fish, but the waters would not conceal her divine nature. Thereafter, she took the form of a mermaid — human above the waist, fish below — though the earliest representations of Atargatis showed her as being a fish with a human head and legs, similar to the Babylonian Ea. The Greeks recognized Atargatis under the name Derketo, where she was often conflated with Aphrodite. Prior to 546 B.C., the Milesian philosopher Anaximander proposed that mankind had sprung from an aquatic species of animal. He thought that man with his extended infancy could not have survived, originally, in the manner he does presently. This idea does not appear to have survived Anaximander's death.

A popular Greek legend has Alexander the Great's sister, Thessalonike, turn into a mermaid after her death. She lived, it was said, in the Aegean and when sailors would encountered her, she would ask them only one question: "Is Alexander the king alive?", to which the correct answer would be "He lives and still rules" (Greek:). Any other answer would spur her into a rage, where she transformed into a Gorgon and meant doom for the ship and every sailor onboard.

Mermaids are one of the most famous creatures of popular culture, and are depicted regularly in literature and film. This is likely due to the influence of Hans Christian Andersen's fairytale The Little Mermaid (1836), which has been translated into many languages. Andersen's portrayal, immortalized with a famous bronze sculpture in Copenhagen harbour, has arguably become the standard and has influenced most modern Western depictions of mermaids since it was published. The story has been retold in other films and television programs, and regularly features in collections of fairytales. It has been adapted into various media, the most famous of which is the 1989 Disney movie of the same name.

Various cultures throughout the world have similar figures. They were known to sing sailors to their deaths, like the Siren, or squeeze the life out of drowning men, while trying to rescue them. The Sirens of Greek mythology are sometimes portrayed in later folklore as mermaids; in fact in some languages the name sirena is used interchangeably for both creatures. Other related types of mythical or legendary creature are water fairies (e.g. various water nymphs) and selkies.

Mermaid Syndrom - Sirenomelia
Sirenomelia Sequence [Mermaid Syndrom] is a very rare disorder, congenital structural anomaly characterized by an abnormal development of the caudal region of the body with different degrees of fusion of the lower extremities and bears resemblance to the mermaid of Greek mythology. This deformity is also known as Symmelia, Symposia, Sympus, Uromelia and Monopodia. This condition is found in approximately one out of every 100,000 live births (about as rare as conjoined twins) and is usually fatal within a day or two of birth because of complications associated with the abnormality.

The precise etiology of sirenomelia is not well understood. Many theories have been proposed but none of these is considered conclusive. It has been reported to occur as a result of the use of teratogenic agents. Hibelink et al demonstrated that the intravenous administration of cadmium and lead can produce sirenomelia in the golden hamster. VonLennep et al described the possible teratogenic effects of Vitamin A. Duhemmel et al consider this anomaly as a manifestation of the caudal regression syndrome that is a consequence of abnormal development of structures derived from the caudal mesoderm of the embryo before the fourth week of gestation and extended to various cranio-caudal levels. Maternal diabetes mellitus, genetic predisposition and vascular hypoperfusion have been proposed as possible causative factors.