Monstrous, one-eyed giants have prowled around our imaginations for at least 4,000 years – the oldest known description of such a creature was written on Babylonian tablets found near the Tigris river. The first stories about Cyclops emerged in Greece in the 8th–7th century BC: Homer’s epic poem Odyssey, followed by Hesiodus’ epic poem Theogonia, and later Euripides’ play Cyclops in the 5th century BC. What inspired these tales of a “horrid creature, not like a human being at all”? In 1914, the paleontologist Othenio Abel suggested that Ancient Greeks found local fossils of pygmy elephant skulls which contained a large, central nasal cavity resembling a single eye socket. You can read more about this idea in a previous Charged article!
Descriptions of Cyclops also appear in scientific literature and records throughout history. In 1619, the Italian physician and philosopher Fortunio Liceti wrote a letter about cyclopia, a rare congenital malformation that gives the appearance of a single median eye. Cyclopia gained attention in the 18th–19th century with the rise of teratology, the study of congenital malformations. During this time, Willem Vrolik, a Dutch anatomist and pathologist, developed a collection of human and animal cyclops specimens, and the French naturalist Geoffroy Saint-Hilaire created the “cyclocephaly” classification for facial anomalies affecting the eyes. It was not until the 20th century that scientists developed a better understanding of this rare condition.
Cyclopia occurs in about 0.001% of births with an excess of females and twins. Half of these infants are stillborn due to brain development being impacted—cyclopia is a type of holoprosencephaly, a birth defect that causes the ventral brain to form incorrectly. The lack of separation between the cerebral hemispheres causes an ependymal (neural) cyst around the center of the forehead, and in some cases the two eyes fuse together. The appearance of a single median eye is exaggerated by deformed orbital bones that cause protrusions above the eye(s) and the appearance of a single nasal cavity.
The exact cause of cyclopia remains unknown. It is likely that exposure to teratogenic environmental factors or chromosomal abnormalities contribute to this unusual and deadly congenital development. A study with mice investigated the relevance of Hedgehog (Hh) proteins which are responsible for inducing cells in the ventral brain region of the embryo. Specifically, mutations in Sonic hedgehog (Shh) proteins produced cyclopia in some infant mice. Another study found that transforming growth-factor-B (TGF-B) genes could play a role—in zebrafish, the cyclops (cyc) gene is believed to signal the TGF-B genes to develop the ventral brain and identify the midline where the hemispheres will split, so mutations in the cyc gene can produce cyclopia. However, it will take a lot of research to untangle our brains and truly understand the medical factors behind the mythical Cyclops.
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Blader, P., & Strahle, U. (1998). Casting an eye over cyclopia. Nature, 395(6698), 112-3. doi:http://dx.doi.org/10.1038/25836
Homer. (1999). The Odyssey (S. Butler, Trans.). Urbana, Illinois: Project Gutenberg. Retrieved from https://www.gutenberg.org/ebooks/1727
Kalantzis, G. C., Tsiamis, C. B., & Poulakou-Rebelakou, E. (2013). Cyclopia: From greek antiquity to medical genetics. Italian Journal of Anatomy and Embryology, 118(3), 256-62. Retrieved from https://go.openathens.net/redirector/gatech.edu?url=https://search.proquest.com/scholarly-journals/cyclopia-greek-antiquity-medical-genetics/docview/1497034944/se-2?accountid=11107
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